**Compostable Polymers and Nanocomposites — A Big Chance for Planet Earth**

Gity Mir Mohamad Sadeghi and Sayaf Mahsa

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/59398

#### **1. Introduction**

In this chapter, the significance of composting composites and nanocomposites based on biobased polymers used in various applications to reduce the amount of solid waste in landfills is presented. Furthermore, composting methods to produce compostable materials and international standard test methods for evaluation of the above mentioned materials have been explained.

Our every action must have an impact on the well-being of our planet, and our everyday decisions can help create a better world for all. Reducing the amount of solid waste in landfills and the addition of nutrient-rich organic matter are the help that composting gives to the Earth because organic content in the soil encourages the passage of air and water. The introduction of various contaminants into natural environments that have resulted in instability, disorder, harm, or discomfort to an ecosystem is known as pollution and includes different forms such as air, soil, water, sound, etc.

Chemicals that are released into the ground deliberately, accidentally, or by underground leakage have resulted in soil pollution, and these can include hydrocarbons, herbicides, pesticides, chlorinated hydrocarbons, and heavy metals such a chromium and cadmium. Natural and man-made sources such as vehicle emissions and other principal sources includ‐ ing chemical plants, petrochemical plants, PVC factories, and other plastic factories have caused air pollution [1, 2].

Waste can result in the obstruction of storm water runoff which causes stagnant water bodies to form, hence becoming a means of disease. Furthermore, waste dumped near water sources results in contamination of the groundwater source as well as the water body.

© 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Plastic pollution is also a serious threat to some of the world's oceans. Ocean currents cause plastic detritus to cumulate together to form large garbage patches. Therefore, polymer pollution is a serious threat that is presented as follows.

#### **1.1. Polymer pollution: A serious threat**

Polymers are materials that the earth cannot digest and cause serious damage to the environ‐ ment during their production and disposal process. All polymers produced thus far still exist and could remain with us for more than hundreds of years. Polymers break down into smaller particles which attract toxic materials and are swallowed by wildlife in the ocean or land and then contaminate our food chain. The growth rate in polymer production is significantly fast. Figure 1 presents rates of past and future plastic growth during a 60-year time period (1960 to 2020) through a semilog graph. In order for any of these four plastic categories to slightly change their order of magnitude, a long time duration is necessary. In addition, among the different plastics, polycarbonate and some alloys might be ones that achieve the commodity plastics status by 2020. An average of 8.1 % annual growth rate brought solid polymers from seven million tons to 196 million tons between the years 1960 and 2005. This number will continue to escalate to over 365 and 540 million tons in 2015 and 2020, respectively, with a more conservative yearly rate of 6.5 %. The overall production/consumption of plastics worldwide at the turn of the century had an average yearly growth rate of 15 %. In other words, the growth rate doubled every five years, until around 1979, when the trend broke at the first oil shock. Such a high growth rate was seen only then, as the average annual growth rate of plastics went from 15 % between the years 1960 and 1974 to 8 % between the years 1974 and 2000 and 2005. The expanding and fast developing markets, with more than a 10–15 % growth rate per year, were similar to the times of great success for the plastics built up in Europe, the USA, and Japan, in the 1960–1975 era [2].

World plastics production includes thermoplastics, polyurethanes, thermosets, elastomers, adhesives, coatings and sealants, and PP fibers, not including PET-, PA- and Polyacryl fibers as shown in Fig. 2 that is reported by the PlasticsEurope Market Research Group (PEMRG) [3]. Once the polymer is produced, the harm introduced is almost permanent. This results in a serious waste disposal and pollution problem. Solid waste is significantly increasing within the world. Where municipal waste is concerned, from the year 1995 to 2003, the average European citizen's municipal waste generation has continually increased by about 2 % per year from 204 million tons (457 kg/person) in 1995 to 243 million tons (534 kg/person) in 2003 [5]. The proportion of postconsumer waste in EU-27, Norway, and Switzerland according to the function could be observed in Fig 3. It is extremely difficult to measure the state of plastic waste. Statistics show that in 2008, an average of 24.9 megatons of plastic waste [4, 5, 6] was produced in EU-27, Norway, and Switzerland; however, confirming this distribution is quite difficult. Conventional polymers which are made from a hydrocarbon base, such as polyethy‐ lene, polypropylene, polystyrene, polyethylene, terephthalate, etc., are virtually nonbiode‐ gradable [6].

In addition to their extreme effects on the ecosystem, chemicals can cause a range of illnesses including birth defects, cancer, and damage to the nervous and immune system and also affect the blood and the kidneys. Many of these toxic substances are also given off during the Compostable Polymers and Nanocomposites — A Big Chance for Planet Earth http://dx.doi.org/10.5772/59398 65

**Figure 1.** Rates of past and future plastics growth, over a 60-year time span [2]

Plastic pollution is also a serious threat to some of the world's oceans. Ocean currents cause plastic detritus to cumulate together to form large garbage patches. Therefore, polymer

Polymers are materials that the earth cannot digest and cause serious damage to the environ‐ ment during their production and disposal process. All polymers produced thus far still exist and could remain with us for more than hundreds of years. Polymers break down into smaller particles which attract toxic materials and are swallowed by wildlife in the ocean or land and then contaminate our food chain. The growth rate in polymer production is significantly fast. Figure 1 presents rates of past and future plastic growth during a 60-year time period (1960 to 2020) through a semilog graph. In order for any of these four plastic categories to slightly change their order of magnitude, a long time duration is necessary. In addition, among the different plastics, polycarbonate and some alloys might be ones that achieve the commodity plastics status by 2020. An average of 8.1 % annual growth rate brought solid polymers from seven million tons to 196 million tons between the years 1960 and 2005. This number will continue to escalate to over 365 and 540 million tons in 2015 and 2020, respectively, with a more conservative yearly rate of 6.5 %. The overall production/consumption of plastics worldwide at the turn of the century had an average yearly growth rate of 15 %. In other words, the growth rate doubled every five years, until around 1979, when the trend broke at the first oil shock. Such a high growth rate was seen only then, as the average annual growth rate of plastics went from 15 % between the years 1960 and 1974 to 8 % between the years 1974 and 2000 and 2005. The expanding and fast developing markets, with more than a 10–15 % growth rate per year, were similar to the times of great success for the plastics built up in Europe, the

World plastics production includes thermoplastics, polyurethanes, thermosets, elastomers, adhesives, coatings and sealants, and PP fibers, not including PET-, PA- and Polyacryl fibers as shown in Fig. 2 that is reported by the PlasticsEurope Market Research Group (PEMRG) [3]. Once the polymer is produced, the harm introduced is almost permanent. This results in a serious waste disposal and pollution problem. Solid waste is significantly increasing within the world. Where municipal waste is concerned, from the year 1995 to 2003, the average European citizen's municipal waste generation has continually increased by about 2 % per year from 204 million tons (457 kg/person) in 1995 to 243 million tons (534 kg/person) in 2003 [5]. The proportion of postconsumer waste in EU-27, Norway, and Switzerland according to the function could be observed in Fig 3. It is extremely difficult to measure the state of plastic waste. Statistics show that in 2008, an average of 24.9 megatons of plastic waste [4, 5, 6] was produced in EU-27, Norway, and Switzerland; however, confirming this distribution is quite difficult. Conventional polymers which are made from a hydrocarbon base, such as polyethy‐ lene, polypropylene, polystyrene, polyethylene, terephthalate, etc., are virtually nonbiode‐

In addition to their extreme effects on the ecosystem, chemicals can cause a range of illnesses including birth defects, cancer, and damage to the nervous and immune system and also affect the blood and the kidneys. Many of these toxic substances are also given off during the

pollution is a serious threat that is presented as follows.

64 Recycling Materials Based on Environmentally Friendly Techniques

**1.1. Polymer pollution: A serious threat**

USA, and Japan, in the 1960–1975 era [2].

gradable [6].

**Figure 2.** World plastics production 1950–2011 shows that the plastics industry continues to grow rapidly [3]

**Figure 3.** Proportion of postconsumer waste [5]

recycling of polymer. As is the case with all other chemical substances, the "disposal" of polymer seems to be a fallacy.

Polymeric wastes cause drain blockage and irreparable damages to the urban sewage systems. Plastic wastes that are constantly dumped into rivers, streams, and sea pollute the water, soil, marine life, and also the air we breathe. Clogged drains can create extremely bad conditions for mosquitoes to gather while also causing flooding during the monsoon.

Fig. 4 shows Pacific Garbage Patch, as a result of the mentioned condition [7]. Since plastic does not undergo bacterial decomposition, landfilling using plastic would mean preserving the poison forever. Stability of plastics to degradation, closing of landfill sites, and growing water and land pollution problems caused lots of concern about polymers. Waste problem and its serious impact on the environment lead to new interest in the area of degradable polymers. Waste plastic fills bird's stomachs and slowly kills them (see Fig. 5). The interest in environmental issues is growing up; also there are increasing demands to develop materials that do not burden the environment. With the excessive use of plastics and increasing pressure being placed on available capacities for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has led to its increased importance in the past few years [8].

Polymers are made of major chemicals that are highly toxic and pose a serious threat to all living species on the planet Earth. Some of the polymer components such as benzene and vinyl chloride are proven to cause cancer, and other gases and liquid hydrocarbons bring about great damages to the earth and air. The toxic substances that are emitted during polymer production are synthetic chemicals like ethylene oxide, benzene, and xylene [9]. Figures 6a and 6b show acid rain production cycle and huge smoke that are produced by polymers production plants. Compostable Polymers and Nanocomposites — A Big Chance for Planet Earth http://dx.doi.org/10.5772/59398 67

**Figure 4.** Pacific Garbage Patch [7]

recycling of polymer. As is the case with all other chemical substances, the "disposal" of

Polymeric wastes cause drain blockage and irreparable damages to the urban sewage systems. Plastic wastes that are constantly dumped into rivers, streams, and sea pollute the water, soil, marine life, and also the air we breathe. Clogged drains can create extremely bad conditions

Fig. 4 shows Pacific Garbage Patch, as a result of the mentioned condition [7]. Since plastic does not undergo bacterial decomposition, landfilling using plastic would mean preserving the poison forever. Stability of plastics to degradation, closing of landfill sites, and growing water and land pollution problems caused lots of concern about polymers. Waste problem and its serious impact on the environment lead to new interest in the area of degradable polymers. Waste plastic fills bird's stomachs and slowly kills them (see Fig. 5). The interest in environmental issues is growing up; also there are increasing demands to develop materials that do not burden the environment. With the excessive use of plastics and increasing pressure being placed on available capacities for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has led to its increased importance in the past

Polymers are made of major chemicals that are highly toxic and pose a serious threat to all living species on the planet Earth. Some of the polymer components such as benzene and vinyl chloride are proven to cause cancer, and other gases and liquid hydrocarbons bring about great damages to the earth and air. The toxic substances that are emitted during polymer production are synthetic chemicals like ethylene oxide, benzene, and xylene [9]. Figures 6a and 6b show acid rain production cycle and huge smoke that are produced by polymers production plants.

for mosquitoes to gather while also causing flooding during the monsoon.

polymer seems to be a fallacy.

**Figure 3.** Proportion of postconsumer waste [5]

66 Recycling Materials Based on Environmentally Friendly Techniques

few years [8].

**Figure 5.** Bird corpse, photo: Chris Jordan

Contaminants such as persistent organic pollutants (POPs) are also attracted by polymeric waste, especially in marine life. Many of these contaminants are hydrophobic; therefore, mixing or binding with water is not possible.

The role of plastics waste on the impact of the toxic chemicals is not evident. These chemicals could potentially move to clean environments by plastics, and when taken in by wildlife, the chemicals could transfer into the organism's system by plastics. However, in certain condi‐ tions, plastic could become less available to wildlife and act as a sink, particularly if they are Fig. 5. Bird corpse, photo: Chris Jordan

Polymers are made of major chemicals that are highly toxic and pose a serious threat to all living species on the planet Earth. Some of the polymer components such as benzene and vinyl chloride are proven to cause cancer, and other

emitted during polymer production are synthetic chemicals like ethylene oxide, benzene, and xylene [9]. Figures 6a and

Fig. 6a. Production cycle of acid rain in the Earth [10] Fig. 6b. Huge dangerous smoke:

plastics. However, in certain conditions, plastic could become less available to wildlife and act as a sink, particularly if

**Figure 6.** (a). Production cycle of acid rain in the Earth [10] (b). Huge dangerous smoke: A result of plastics production [10]

buried on the seafloor. Microplastics have a large surface area-to-volume ratio and are prone to make chemicals more available to wildlife and the environment compared to larger-sized plastics [11]. A result of plastics production [10] Contaminants such as persistent organic pollutants (POPs) are also attracted by polymeric waste, especially in marine

However, microplastics could pass through the digestive system faster than larger plastics once they have been ingested, potentially giving less chance for chemicals to be absorbed into the circulatory system [8]. A descriptive example is presented in the next section. life. Many of these contaminants are hydrophobic; therefore, mixing or binding with water is not possible. The role of plastics waste on the impact of the toxic chemicals is not evident. These chemicals could potentially move to clean environments by plastics, and when taken in by wildlife, the chemicals could transfer into the organism's system by

#### *1.1.1. Descriptive example* they are buried on the seafloor. Microplastics have a large surface area-to-volume ratio and are prone to make chemicals

In 2002, the production of PET worldwide was 26 million tons which is expected to rise to 85 million tons in 2018. Numerous postconsumer PET products, especially bottles and containers, are not directly hazardous to the environment. You can see a photograph in Fig. 7 that shows the Caspian Sea beach captured by the author. However, its substantial volume fraction in solid waste streams, high resistance to the atmosphere, poor biodegradability, and photo degradability has caused serious problems. Each year, it is estimated that a billion plastic bottles are disposed, while recycling only one plastic bottle can conserve enough energy to light a 60 W light bulb for up to 6 h [12]. more available to wildlife and the environment compared to larger-sized plastics [11]. However, microplastics could pass through the digestive system faster than larger plastics once they have been ingested, potentially giving less chance for chemicals to be absorbed into the circulatory system [8]. A descriptive example is presented in the next section.

4

PET waste can be seen everywhere, so the world production rate of PET waste grows fast (Fig. 8). A greater necessity is felt for the recycling of this product.

Fig. 7. PET waste as a threat, serious cause of concern to the environmentalists **Figure 7.** PET waste as a threat, serious cause of concern to the environmentalists

In Singapore, 684, 400 tons of plastic wastes were generated in 2008, and the recycling rate was 9 %. Even though PET has major advantages for use, such as its nontoxic nature, durability, and crystal-clear transparency, its nonbiodegradability seems to be the serious cause of concern to environmentalists [13]. PET waste can be seen everywhere, so the world production rate of PET waste grows fast (Fig. 8). A greater necessity is felt for the recycling of this product. In Singapore, 684,400 tons of plastic wastes were generated in 2008, and the recycling rate was 9 %. Even though PET has major advantages for use, such as its nontoxic nature, durability, and crystal-clear transparency, its nonbiodegradability seems to be the serious cause of concern to environmentalists [13]. Since it is not appropriate to dispose of waste PET by landfills, other recycling methods of waste PET products including physical and chemical recycling have been developed. Chemical recycling of PET includes chemolysis of the polyester

PET waste can be seen everywhere, so the world production rate of PET waste grows fast (Fig. 8). A greater necessity is

Since it is not appropriate to dispose of waste PET by landfills, other recycling methods of waste PET products including physical and chemical recycling have been developed. Chemical recycling of PET includes chemolysis of the polyester with an excess of reactants such as water (hydrolysis), alcohols (alcoholysis), glycols (glycolysis), amines [14], and ammonia (ammo‐ nolysis) [15]. felt for the recycling of this product. In Singapore, 684,400 tons of plastic wastes were generated in 2008, and the recycling rate was 9 %. Even though PET has major advantages for use, such as its nontoxic nature, durability, and crystal-clear transparency, its nonbiodegradability seems to be the serious cause of concern to environmentalists [13]. Since it is not appropriate to dispose of waste PET by landfills, other recycling methods of waste PET products including physical and chemical recycling have been developed. Chemical recycling of PET includes chemolysis of the polyester with an excess of reactants such as water (hydrolysis), alcohols (alcoholysis), glycols (glycolysis), amines [14], and with an excess of reactants such as water (hydrolysis), alcohols (alcoholysis), glycols (glycolysis), amines [14], and ammonia (ammonolysis) [15].

However, microplastics could pass through the digestive system faster than larger plastics once they have been ingested, potentially giving less chance for chemicals to be absorbed into the circulatory system [8]. A descriptive example is Fig. 8 PET waste can be seen everywhere (left image), so the world production rate of PET waste grows fast (right image) **1.2 Which Way Must Be Chosen to Save Our Planet? [7] Figure 8.** PET waste can be seen everywhere (left image), so the world production rate of PET waste grows fast (right image) Others believe that polymers refuse any attempt at disposal, whether through recycling, burning, or landfilling. When one hazard is done away with, it paves the way for another to come. One of the only ways to overcome the noxious danger of plastic pollution is to reduce the use of plastic and completely avoid it if possible.

It is believed that any attempt to dispose of plastic through landfills is also harmful. In addition to the toxic seepage from

#### the landfill which caused to contamination of precious water sources, the waste mass hinders the flow of groundwater. As landfills are also prone to leakages, the lead and cadmium in the wastes mix with rain water and then drip through the **1.2. Which way must be chosen to save our planet? [7]**

pollution will have long-term benefits for the generations to come.

ammonia (ammonolysis) [15].

buried on the seafloor. Microplastics have a large surface area-to-volume ratio and are prone to make chemicals more available to wildlife and the environment compared to larger-sized

**Figure 6.** (a). Production cycle of acid rain in the Earth [10] (b). Huge dangerous smoke: A result of plastics production

Fig. 5. Bird corpse, photo: Chris Jordan

Polymers are made of major chemicals that are highly toxic and pose a serious threat to all living species on the planet Earth. Some of the polymer components such as benzene and vinyl chloride are proven to cause cancer, and other gases and liquid hydrocarbons bring about great damages to the earth and air. The toxic substances that are emitted during polymer production are synthetic chemicals like ethylene oxide, benzene, and xylene [9]. Figures 6a and

6b show acid rain production cycle and huge smoke that are produced by polymers production plants.

However, microplastics could pass through the digestive system faster than larger plastics once they have been ingested, potentially giving less chance for chemicals to be absorbed into

life. Many of these contaminants are hydrophobic; therefore, mixing or binding with water is not possible.

In 2002, the production of PET worldwide was 26 million tons which is expected to rise to 85 million tons in 2018. Numerous postconsumer PET products, especially bottles and containers, are not directly hazardous to the environment. You can see a photograph in Fig. 7 that shows the Caspian Sea beach captured by the author. However, its substantial volume fraction in solid waste streams, high resistance to the atmosphere, poor biodegradability, and photo degradability has caused serious problems. Each year, it is estimated that a billion plastic bottles are disposed, while recycling only one plastic bottle can conserve enough energy to

more available to wildlife and the environment compared to larger-sized plastics [11].

PET waste can be seen everywhere, so the world production rate of PET waste grows fast (Fig.

the circulatory system [8]. A descriptive example is presented in the next section.

(a) (b)

plastics [11].

[10]

68 Recycling Materials Based on Environmentally Friendly Techniques

*1.1.1. Descriptive example*

light a 60 W light bulb for up to 6 h [12].

presented in the next section.

8). A greater necessity is felt for the recycling of this product.

4 ground and drain into nearby streams and lakes and other water sources, poisoning the water we use. Others believe that polymers refuse any attempt at disposal, whether through recycling, burning, or landfilling. When one hazard is done away with, it paves the way for another to come. One of the only ways to overcome the noxious danger of plastic pollution is to reduce the use of plastic and completely avoid it if possible. Some people are of the belief that one of the ways to cut off the hazards of polymer pollution is to reduce the use of polymer and thereby force a reduction in its production. It is best to refrain from using plastic whenever and wherever you can. It is better to opt for the use of a cloth bag when carrying your groceries. Any attempt we make to end polymer It is believed that any attempt to dispose of plastic through landfills is also harmful. In addition to the toxic seepage from the landfill which caused to contamination of precious water sources, the waste mass hinders the flow of groundwater. As landfills are also prone to leakages, the lead and cadmium in the wastes mix with rain water and then drip through the ground and drain into nearby streams and lakes and other water sources, poisoning the water we use.

5

5

Others believe that polymers refuse any attempt at disposal, whether through recycling, burning, or landfilling. When one hazard is done away with, it paves the way for another to come. One of the only ways to overcome the noxious danger of plastic pollution is to reduce the use of plastic and completely avoid it if possible.

Some people are of the belief that one of the ways to cut off the hazards of polymer pollution is to reduce the use of polymer and thereby force a reduction in its production. It is best to refrain from using plastic whenever and wherever you can. It is better to opt for the use of a cloth bag when carrying your groceries. Any attempt we make to end polymer pollution will have long-term benefits for the generations to come.

**Figure 9.** Burning a polymer caused releases of poisonous chemicals. Photo courtesy of Flickr

Waste strategies used across the globe are quite similar and are based upon the prevention and recycling of waste. For example, Japan has extensive rules and regulations pertaining to waste and other sustainable production and consumption policies under the "3Rs – reducing, reusing, and recycling" umbrella.

The European Union has its own strategy in dealing with waste, by preventing waste from the start, recycling waste, and optimizing the disposal of waste [5].

By recycling polymers, we are only returning them back into the marketplace and eventually into the environment, hence causing no reduction in its use. The recycled polymer is degraded in quality and requires the production of a newer polymer to make the original product. Burning a polymer has its own disadvantages. When burned, it could release a great number of poisonous chemicals into the air (Fig. 9). In addition to these dangers, recycling polymers is not very economical. Studies conducted by many "Public Interest Research Groups" have indicated that it is also a very dirty task, requiring hard physical work. Recycling of polymer has been connected to skin and respiratory problems as a result of being exposed to toxic fumes, especially hydrocarbons and residues emitted during the process [7], [12].

#### *1.2.1. Serious response to polymer pollution*

Others believe that polymers refuse any attempt at disposal, whether through recycling, burning, or landfilling. When one hazard is done away with, it paves the way for another to come. One of the only ways to overcome the noxious danger of plastic pollution is to reduce

Some people are of the belief that one of the ways to cut off the hazards of polymer pollution is to reduce the use of polymer and thereby force a reduction in its production. It is best to refrain from using plastic whenever and wherever you can. It is better to opt for the use of a cloth bag when carrying your groceries. Any attempt we make to end polymer pollution will

the use of plastic and completely avoid it if possible.

70 Recycling Materials Based on Environmentally Friendly Techniques

have long-term benefits for the generations to come.

**Figure 9.** Burning a polymer caused releases of poisonous chemicals. Photo courtesy of Flickr

start, recycling waste, and optimizing the disposal of waste [5].

reusing, and recycling" umbrella.

Waste strategies used across the globe are quite similar and are based upon the prevention and recycling of waste. For example, Japan has extensive rules and regulations pertaining to waste and other sustainable production and consumption policies under the "3Rs – reducing,

The European Union has its own strategy in dealing with waste, by preventing waste from the

By recycling polymers, we are only returning them back into the marketplace and eventually into the environment, hence causing no reduction in its use. The recycled polymer is degraded in quality and requires the production of a newer polymer to make the original product. Burning a polymer has its own disadvantages. When burned, it could release a great number of poisonous chemicals into the air (Fig. 9). In addition to these dangers, recycling polymers is not very economical. Studies conducted by many "Public Interest Research Groups" have indicated that it is also a very dirty task, requiring hard physical work. Recycling of polymer

As regards to the increasing challenges of waste production and its management, the European Parliament and the Council have fostered a number of official orders. These orders are critical to ensure that waste is recovered or disposed of without harming the environment and human health.

According to the European official order on packaging and packaging waste [13], the man‐ agement of packaging and packaging waste's utmost priority should be the prevention of packaging waste. In addition, the reuse of packaging, recycling, and other forms of recovering packaging waste and, therefore the reduction of the final disposal of such waste should be considered fundamental.

As observed in Fig. 10, some solutions are provided for reducing polymer pollution. Preven‐ tion refers to the reduction of the quantity of materials and substances that are included in packaging and packaging waste that can be harmful to the environment. It includes developing clean production methods and technology for packaging and packaging waste at the produc‐ tion process level for marketing, distribution, and utilization stages. Reuse is the process in which packaging is refilled or used once more for the same purpose which it was produced. Recovery includes operations such as using a fuel to generate energy, recycling of organic substances which are not used as solvents, etc. (including composting and other biological transformation processes). Energy recovery is defined as the use of combustible packaging waste in order to generate energy by completely burning the substance (incineration) with or without other wastes but with recovery of heat.

Recycling is a process in which waste materials are reprocessed for the original purpose or for other purposes including organic recycling but excluding energy recovery.

Disposal operations include deposit into or onto land (e.g., landfilling), incineration, etc. Compostable polymers, known as biological or organic recycling, are a valuable recovery option.

The EU official order on packaging and packaging waste defines organic recycling as the aerobic (composting) or anaerobic (bio methanization) treatment of the biodegradable parts of packaging waste under controlled conditions and using microorganisms. This process produces stabilized organic residues or methane. It is noteworthy to mention that landfills are not considered as a form of organic recycling.

Most developed countries have put the waste management hierarchy to use, i.e., minimization, recovery and transformation, and land disposal, using strategies that depend on factors such as population density, transportation infrastructure, and socioeconomic and environmental regulations. Let us also contribute our part, and save our environment from polymer pollution

**Figure 10.** Composting, as a solution to solve Earth problem

to make it a better environment for the future. To do so, one of the best ways to reduce the hazards of polymer pollution is changing them to compost.

#### **2. Compost [11, 23]**

Compost is a versatile product and obtained from composting, biodegradation of organic waste that is industrially, commercially, or domestically produced. Its fundamental use is in conditioning and fertilizing soil by the addition of humus, nutrients, and beneficial soil bacteria, with a wide range of specific applications.

Methane is an organic material produced via organic materials "anaerobically" without air in landfills and is a gas with 25 times the global warming impact of CO2! This same organic mulch helps to absorb carbon back into the soil if it is composted.

#### **Better Soil, Better Life, Better Future**

It is interesting to note that about 60 % of the garbage Australians throw out could be put to better use as mulch to improve soil quality and in the garden as compost.

Composts improve soil quality, assist plant growth, increase water holding capacity, store carbon in the soil, and reduce the need for chemical fertilizer and pesticides.

Earthworms flourish in enriched soils. Activities of earthworms help release essential nutrients strengthen plants and also increase their resistance to various diseases.

Compost is an organic matter that has been decomposed and recycled as a fertilizer and soil strengthener. Compost is a very important component of organic farming. Simply put, composting process merely requires making a heap of wetted organic matter that is known as green waste (leaves, food waste) and waiting for the materials to decompose to humus after a period of weeks or months. Composting nowadays includes a multi-step monitored process

7

with exact inputs of air, water, and carbon-rich and nitrogen-rich materials. In order to assist the decomposition process, the plant matter is shredded, water is added, and proper aeration is ensured by regularly turning the mixture. Worms and fungi can also further decompose or break up the material. Aerobic bacteria and fungi manage a chemical process by converting the inputs into heat, carbon dioxide, and ammonium. Ammonium is a form of nitrogen (NH4) used by plants. When existing ammonium is not used by plants, it is converted by bacteria into nitrates (NO3) through a process known as nitrification. Compost production is shown in Fig. 11. increase their resistance to various diseases. Compost is an organic matter that has been decomposed and recycled as a fertilizer and soil strengthener. Compost is a very important component of organic farming. Simply put, composting process merely requires making a heap of wetted organic matter that is known as green waste (leaves, food waste) and waiting for the materials to decompose to humus after a period of weeks or months. Composting nowadays includes a multi-step monitored process with exact inputs of air, water, and carbon-rich and nitrogen-rich materials. In order to assist the decomposition process, the plant matter is shredded, water is added, and proper aeration is ensured by regularly turning the mixture. Worms and fungi can also further decompose or break up the material. Aerobic bacteria and fungi manage a chemical process by converting the inputs into heat, carbon dioxide, and ammonium. Ammonium is a form of nitrogen (NH4) used by plants. When existing ammonium is not used by plants, it is converted by bacteria into nitrates (NO3) through a process known as nitrification.

using microorganisms. This process produces stabilized organic residues or methane. It is noteworthy to mention that

Most developed countries have put the waste management hierarchy to use, i.e., minimization, recovery and transformation, and land disposal, using strategies that depend on factors such as population density, transportation infrastructure, and socioeconomic and environmental regulations. Let us also contribute our part, and save our environment from polymer pollution to make it a better environment for the future. To do so, one of the best ways to

Compost is a versatile product and obtained from composting, biodegradation of organic waste that is industrially, commercially, or domestically produced. Its fundamental use is in conditioning and fertilizing soil by the addition of

Methane is an organic material produced via organic materials "anaerobically" without air in landfills and is a gas with 25 times the global warming impact of CO2! This same organic mulch helps to absorb carbon back into the soil if it is

It is interesting to note that about 60 % of the garbage Australians throw out could be put to better use as mulch to

Earthworms flourish in enriched soils. Activities of earthworms help release essential nutrients strengthen plants and also

landfills are not considered as a form of organic recycling.

**2. Compost [11, 23]** 

composted**.**

**Better Soil, Better Life, Better Future**

Compost production is shown in Fig. 11.

improve soil quality and in the garden as compost.

reduce the hazards of polymer pollution is changing them to compost.

humus, nutrients, and beneficial soil bacteria, with a wide range of specific applications.

#### Fig. 11. Compost **Figure 11.** Compost

to make it a better environment for the future. To do so, one of the best ways to reduce the

Compost is a versatile product and obtained from composting, biodegradation of organic waste that is industrially, commercially, or domestically produced. Its fundamental use is in conditioning and fertilizing soil by the addition of humus, nutrients, and beneficial soil

Methane is an organic material produced via organic materials "anaerobically" without air in landfills and is a gas with 25 times the global warming impact of CO2! This same organic mulch

It is interesting to note that about 60 % of the garbage Australians throw out could be put to

Composts improve soil quality, assist plant growth, increase water holding capacity, store

Earthworms flourish in enriched soils. Activities of earthworms help release essential nutrients

Compost is an organic matter that has been decomposed and recycled as a fertilizer and soil strengthener. Compost is a very important component of organic farming. Simply put, composting process merely requires making a heap of wetted organic matter that is known as green waste (leaves, food waste) and waiting for the materials to decompose to humus after a period of weeks or months. Composting nowadays includes a multi-step monitored process

hazards of polymer pollution is changing them to compost.

**Figure 10.** Composting, as a solution to solve Earth problem

72 Recycling Materials Based on Environmentally Friendly Techniques

bacteria, with a wide range of specific applications.

**Better Soil, Better Life, Better Future**

helps to absorb carbon back into the soil if it is composted.

better use as mulch to improve soil quality and in the garden as compost.

carbon in the soil, and reduce the need for chemical fertilizer and pesticides.

strengthen plants and also increase their resistance to various diseases.

**2. Compost [11, 23]**

Compost is rich in nutrients that are used in gardens, landscaping, horticulture, and agricul‐ ture. Compost has itself advantages for the land in many ways, including as a soil conditioner, as a fertilizer, as an additive of vital humus or humic acids, and finally as a natural pesticide for soil. Compost is useful for erosion control, land and stream reclamation, wetland con‐ struction, and as a landfill cover in various ecosystems. Organic ingredients that are considered useful for composting can also be used to generate biogas through anaerobic digestion. Anaerobic digestion is quickly replacing composting in some parts of the world (especially central Europe) as a main means of downcycling waste organic matter.


**Table 1.** Benefits of Using Compost [15] (taken from www.epa.gov)

### **3. Applications of compost [2]**

Compost is used as an organic fertilizer, to improve and condition soil, to manufacture topsoil, as a growing medium and mulch for use in:


There are a variety of benefits in using compost on roadside applications (Table 1). In the following section, these benefits are discussed in greater detail.

#### **3.1. Improved structure**

Compost has a significant impact on the physical structure of soil. In fine-textured (clay, clay loam) soils, adding compost can reduce bulk density, improve workability and porosity, and enhance its gas and water permeability, thus reducing erosion. When an adequate amount is used, its addition can have both an immediate and long-term positive effect on soil structure. It opposes compaction in fine-textured soils and enhances water-holding capacity and enriches soil aggregation in coarse-textured (sandy) soils. The high degree of organic matter decom‐ position results in a stable residue known as humus. The components of humus act as a kind of soil adhesive and hold the particles together, making them more resistant to erosion and improving the soil's ability to hold moisture. With its humus content, compost has soil-binding properties.

#### **3.2. Moisture management**

Drought resistance and efficient water utilization can be enhanced by adding compost. As a result, the intensity and frequency of irrigation may be decreased. Whereas compost can maintain many times its own weight in moisture, indeed its use can greatly contribute to establish roadside plantings. Furthermore, studies have suggested that adding compost in a sandy soil can facilitate moisture dispersion. Using of compost caused to allowing the movement of water laterally, more lightly from its point of application.

#### **3.3. Modifies and stabilizes pH**

**3. Applications of compost [2]**

**•** Agriculture (intensive, organic)

**•** Horticulture

**•** Potting

**•** Nurseries

**•** Greenhouses

**•** Silviculture

properties.

**3.2. Moisture management**

**•** Private gardens

**•** Landscaping (e.g., parks)

**•** Ground rehabilitation

**3.1. Improved structure**

**•** Growing fruit and producing wine

as a growing medium and mulch for use in:

74 Recycling Materials Based on Environmentally Friendly Techniques

Compost is used as an organic fertilizer, to improve and condition soil, to manufacture topsoil,

There are a variety of benefits in using compost on roadside applications (Table 1). In the

Compost has a significant impact on the physical structure of soil. In fine-textured (clay, clay loam) soils, adding compost can reduce bulk density, improve workability and porosity, and enhance its gas and water permeability, thus reducing erosion. When an adequate amount is used, its addition can have both an immediate and long-term positive effect on soil structure. It opposes compaction in fine-textured soils and enhances water-holding capacity and enriches soil aggregation in coarse-textured (sandy) soils. The high degree of organic matter decom‐ position results in a stable residue known as humus. The components of humus act as a kind of soil adhesive and hold the particles together, making them more resistant to erosion and improving the soil's ability to hold moisture. With its humus content, compost has soil-binding

Drought resistance and efficient water utilization can be enhanced by adding compost. As a result, the intensity and frequency of irrigation may be decreased. Whereas compost can maintain many times its own weight in moisture, indeed its use can greatly contribute to establish roadside plantings. Furthermore, studies have suggested that adding compost in a sandy soil can facilitate moisture dispersion. Using of compost caused to allowing the

movement of water laterally, more lightly from its point of application.

following section, these benefits are discussed in greater detail.

Adding compost to soil may modify the pH of the final mix. Depending on the pH of the compost and native soil, adding compost may increase or decrease the pH of the final mix. Therefore, adding neutral or slightly alkaline compost to acidic soil will increase the soil pH if sufficient amounts are added.

In certain conditions, where compost was applied at low amounts such as 10–20 tons per acre, it was found to have an effect on soil pH. Using compost also allows the ability to buffer or stabilize soil pH. This phenomenon could be more useful where it will effectively resist to pH change.

#### **3.4. Increases cation exchange capacity**

Compost can also modify the cation exchange capacity of soils, making it possible to hold nutrients longer. It can also enable crops to utilize nutrients more efficiently while decreasing nutrient loss by leaching. Therefore, soils' fertility and their organic matter content are closely linked. In addition, adding compost can greatly improve the retention of plant nutrients in the root zone by enhancing the cation exchange capacity of sandy soils.

#### **3.5. Provides nutrients**

Compost products include various kinds of macronutrients and micronutrients. While they are often good source of nitrogen, phosphorous, and potassium, composts also include micronutrients that are essential for plant growth. Since composts contain relatively stable sources of organic matter, the nutrients are supplied in a slow-release form. Large amounts of nutrients are normally not found in compost compared to most commercial fertilizers. However, compost is usually added at much greater rates. As a result, it can have a great effect on nutrient availability. By adding compost, significant effects can be observed in both the fertilizer and pH adjustment (lime/sulfur addition). Compost has benefits of both providing nutrition and making the common fertilizer programs more effective.

#### **3.6. Provides soil biota**

Soil organism's activity is very significant in productive soils as well as healthy plants. Their activity depends mainly on the presence of organic matter. Bacteria, protozoa, actinomycetes, and fungi consist soil microorganisms. They are not only found in compost but spread in soil media quickly. Microorganisms have an essential role in organic matter decomposition. After that, humus formation and nutrient availability will occur. Furthermore, microorganisms have benefits for root activity as special fungi do symbiotically with plant roots which help them extract nutrients from soils.

#### **3.7. Suppresses plant diseases**

The level and type of organic matter and microorganisms present in soils may have an influence on the disease rates of many plants. Previous studies have indicated that the increased population of certain microorganisms may suppress specific plant diseases such as pythium and fusarium as well as nematodes. Numerous attempts are being made to optimize the composting process so that the population of these beneficial microbes might increase.

#### **3.8. Binds contaminants**

Another capability of compost is binding heavy metals as well as other contaminants that caused to reduce both their absorption by various plants that is named bioavailability and leachability. As a result, sites that are contaminated with different pollutants could be improved via modifying the native soil with compost. Similar binding effect lets compost be used as a filter for storm water treatment. Furthermore, it has been reported that compost caused to minimize leaching of pesticides in soil systems.

#### **3.9. Horticulture and agriculture**

Compost is used in horticulture in many different contexts. Compost can be mixed with sand, clay, aged sawdust, and other materials in raised-bed gardening in order to create an enriched mix for landscape beds or raised-bed gardens. In this case, compost should be about 30 % of the total mix. To avoid nutrient and oxygen competition with plants, high-quality compost should be used.

Similar to bedding mixes, using of compost up to 30 % based on total mix, depending on maturity and salinity, may be a useful ingredient in potting media in a container garden.

It could be used as a substitute for peat moss, but it must be used in limited amounts due to low porosity and water-holding capacity of peat. Compost has a nutrient content lower than the necessity for supplemental chemical fertilizers, although this must be determined in each case.

Areas that have been excavated areas around the foundation of new buildings are backfilled after construction has been completed, but these planting zones may contain rubble, residues of toxic chemicals, and other undesirable substances. In order to improve the soil in these zones and provide a healthier start for the foundation plantings, it is a good idea to remove the backfill and replace it with a mix of soil and compost.

If the product has course textures and is mature, then two or more inches of compost can be used alone or together with conventional mulch products to keep root zones cool, conserve moisture, and act as a slow-release fertilizer. For a weed barrier, compost can be used at double or triple the amount and be placed on top of a thick layer of newspapers, to replace geomem‐ brane weed barriers. This, however, only holds true for composts that are free of weeds.

For trees and shrubs, mixes of old compost with the native soils can be used as backfill. Immature composts may cause settling and young root disturbance since they are deprived of oxygen. To create new turf areas such as lawns and recreation areas, compost can be applied before seeding or sodding and work into the soil. Compost can be used seasonally as covering and may also be raked into the soil. Some turf farms also use compost to prevent topsoil loss by growing grass in a couple of inches of the material.

Finally, for use in fields, in order to grow corn, wheat, soybeans, and some other crops, compost can be spread on top of the soil by using spreaders pulled behind a tractor or a spreader trucks. The obtained layer after spreading is very thin, about 6 mm which is worked usually into the soil before planting process. When attempting to rebuild poor soils or control erosion, application rates as 25 mm or more are usual.

#### **3.10. Erosion control**

increased population of certain microorganisms may suppress specific plant diseases such as pythium and fusarium as well as nematodes. Numerous attempts are being made to optimize the composting process so that the population of these beneficial microbes might increase.

Another capability of compost is binding heavy metals as well as other contaminants that caused to reduce both their absorption by various plants that is named bioavailability and leachability. As a result, sites that are contaminated with different pollutants could be improved via modifying the native soil with compost. Similar binding effect lets compost be used as a filter for storm water treatment. Furthermore, it has been reported that compost

Compost is used in horticulture in many different contexts. Compost can be mixed with sand, clay, aged sawdust, and other materials in raised-bed gardening in order to create an enriched mix for landscape beds or raised-bed gardens. In this case, compost should be about 30 % of the total mix. To avoid nutrient and oxygen competition with plants, high-quality compost

Similar to bedding mixes, using of compost up to 30 % based on total mix, depending on maturity and salinity, may be a useful ingredient in potting media in a container garden.

It could be used as a substitute for peat moss, but it must be used in limited amounts due to low porosity and water-holding capacity of peat. Compost has a nutrient content lower than the necessity for supplemental chemical fertilizers, although this must be determined in each

Areas that have been excavated areas around the foundation of new buildings are backfilled after construction has been completed, but these planting zones may contain rubble, residues of toxic chemicals, and other undesirable substances. In order to improve the soil in these zones and provide a healthier start for the foundation plantings, it is a good idea to remove the

If the product has course textures and is mature, then two or more inches of compost can be used alone or together with conventional mulch products to keep root zones cool, conserve moisture, and act as a slow-release fertilizer. For a weed barrier, compost can be used at double or triple the amount and be placed on top of a thick layer of newspapers, to replace geomem‐ brane weed barriers. This, however, only holds true for composts that are free of weeds.

For trees and shrubs, mixes of old compost with the native soils can be used as backfill. Immature composts may cause settling and young root disturbance since they are deprived of oxygen. To create new turf areas such as lawns and recreation areas, compost can be applied before seeding or sodding and work into the soil. Compost can be used seasonally as covering and may also be raked into the soil. Some turf farms also use compost to prevent topsoil loss

**3.8. Binds contaminants**

**3.9. Horticulture and agriculture**

should be used.

case.

caused to minimize leaching of pesticides in soil systems.

76 Recycling Materials Based on Environmentally Friendly Techniques

backfill and replace it with a mix of soil and compost.

by growing grass in a couple of inches of the material.

Topsoil loss is a serious ecological issue. A relatively new technology in this realm is the application of compost to control sediment runoff and fight erosion. It has recently been adopted by local authorities, developers, farmers, and other major disturbers of soil as another tool to reduce topsoil loss.

A compost blanket is a layer of compost spread over a disturbed area of soil. While having a high water-holding capacity, compost can remain on the surface to temper the impact of rainfall. Even insignificant amounts can be helpful, but typical recommendations require a 5 cm (2 in.) layer to insure adequate surface coverage. Direct planting into the blanket is also possible.

Compost berms and socks are used alone or together with compost blankets to alleviate the impact of high-volume water discharges. Compost berms are more aesthetically satisfactory than silt fences and remove the need to do away with the berm when the project is complete. After passing the time, compost biodegrades simply and returns to earth. A mesh tube that is stuffed with compost is named a compost sock. The compost socks show better response to heavy equipments and can be anchored, removed, and reused easily. When a sock based on biodegradable fiber is used, it may be left in place to biodegrade; however, since this is not in confidence with the idea of the sock, it is not common.

Other important applications of compost are as follows: Planting media for artificial or constructed wetlands, Cap for a landfill cell when used closely to encourage vegetation and erosion reduction, and erosion control of possibly alleviating damages and restore beauty and functionality to riparian zones in the future.

#### **4. Biodegradation [1, 6, 16]**

Degradation is an irreversible process that leads to great changes of the material structure, usually characterized by a loss of properties and/or fragmentation. Degradation is under the effect of environmental conditions over a certain period of time and consists of one or more steps. Properties such as integrity, molecular weight or structure, and mechanical strength decreases during biodegradation.

According to Dr. Rolf-Joachim Muller's definition [25], biodegradable plastics refer to plastics and non-water-soluble polymer-based materials that degrade via an attack by microorgan‐ isms. It is believed that the biodegradation of plastics is usually a heterogeneous process.

Due to the size and the lack of water solubility of polymeric molecules, microorganisms cannot transport the polymeric material into the cells directly like in most biochemical processes; rather, they must first excrete extracellular enzymes that depolymerize the polymeric chains outside the cells (Fig. 12).

Therefore, if the molar mass of the polymers can be sufficiently reduced to generate watersoluble intermediates, these can be transported into the microorganisms and fed into the appropriate metabolic pathway(s). As a result, the end products of these metabolic processes include water, carbon dioxide, and methane (in the case of anaerobic degradation), together with a new biomass. The extracellular enzymes are too large to penetrate deeply into the polymer material and so act only on the polymer surface. Consequently, the biodegrada‐ tion of plastics is usually a surface erosion process. Although the enzyme-catalyzed chain length reduction of polymers is in many cases the primary process of biodegradation, nonbiotic chemical and physical processes can also act on the polymer, either in parallel or as a first stage solely on the polymer. These nonbiotic effects include chemical hydrolysis, thermal polymer degradation, and oxidation or scission of the polymer chains by irradia‐ tion (photo degradation).

**Figure 12.** General mechanism of plastics biodegradation [28]

#### **4.1. Biodegradable**

According to ASTM D883-99, degradation results from the action of naturally occurring microorganisms such as bacteria, fungi, and algae (according to ASTM D883-99). One of the necessary steps in the testing strategy for materials is testing the biodegradability to define ultimate compostability and a suitable indicator of final compostability. Of course, biodegrad‐ ability is not the same as compatibility. For instance, a potato or a fruit is fully biodegradable but will not compost as such in a composting environment. In a particular context, even geographical or legal context may affect on the definition of compostable, to make fully a biodegradable product "non-compostable."

#### **4.2. Compostable**

Due to the size and the lack of water solubility of polymeric molecules, microorganisms cannot transport the polymeric material into the cells directly like in most biochemical processes; rather, they must first excrete extracellular enzymes that depolymerize the polymeric chains

Therefore, if the molar mass of the polymers can be sufficiently reduced to generate watersoluble intermediates, these can be transported into the microorganisms and fed into the appropriate metabolic pathway(s). As a result, the end products of these metabolic processes include water, carbon dioxide, and methane (in the case of anaerobic degradation), together with a new biomass. The extracellular enzymes are too large to penetrate deeply into the polymer material and so act only on the polymer surface. Consequently, the biodegrada‐ tion of plastics is usually a surface erosion process. Although the enzyme-catalyzed chain length reduction of polymers is in many cases the primary process of biodegradation, nonbiotic chemical and physical processes can also act on the polymer, either in parallel or as a first stage solely on the polymer. These nonbiotic effects include chemical hydrolysis, thermal polymer degradation, and oxidation or scission of the polymer chains by irradia‐

According to ASTM D883-99, degradation results from the action of naturally occurring microorganisms such as bacteria, fungi, and algae (according to ASTM D883-99). One of the necessary steps in the testing strategy for materials is testing the biodegradability to define ultimate compostability and a suitable indicator of final compostability. Of course, biodegrad‐ ability is not the same as compatibility. For instance, a potato or a fruit is fully biodegradable but will not compost as such in a composting environment. In a particular context, even geographical or legal context may affect on the definition of compostable, to make fully a

outside the cells (Fig. 12).

78 Recycling Materials Based on Environmentally Friendly Techniques

tion (photo degradation).

**4.1. Biodegradable**

**Figure 12.** General mechanism of plastics biodegradation [28]

biodegradable product "non-compostable."

A number of standardization committees such as ISO, DIN, ASTM, CEN, and UNI have been working assiduity on compostability testing as well as acceptance criteria or rules for several years. Therefore, the general principles and guidelines regarding testing and basic character‐ istics have been defined which are universally accepted; however, discussion still continues for particular aspects.

According to ISO and ASTM standards, biological degradation during composting caused to produce CO2, water, inorganic compounds as well as biomass at a rate consistent with other known materials that are compostable and do not leave visually toxic or distinguishable residues.

To claim compostability, it should have been proved that packaging can be disintegrated and biodegraded in a composting system (can be shown by standard test methods). Also its biodegradation must complete during the end use of the compost.

The compost should be meeting the relevant quality criteria that include amount of heavy metal, no obviously distinguishable residues, and finally no ecotoxicity.

Environmentally degradable polymers or EDPs can be described as follows:


#### **4.3. Different levels of degradation**

When transferring from a polymeric device insertion to a living organism, regardless of the type, there are different levels of degradation. The various levels, such as isolated organism or the environment itself, are schematized in Fig. 13.

As shown in Fig. 13, it is observed that dissolution and fragmentation processes do not relate to macromolecule scission.

Actually, they show the disappearance of the visible device and hence leave biostable macro‐ molecular compounds as residues. The fragments or the dissolved macromolecules will be retained in the human body, unless they are rejected through boils and abscess or by filtration if molar masses are less than the filtration threshold (10, 000 D to 40, 000 D, depending on the compound).

In the environmental conditions, dissolved macromolecules or the fragments can be stored as organic sand or reached to running or underground water after dissolution.

**Figure 13.** The various levels of degradation for a polymer device

Another stage is the process of macromolecule breakdown to some biostable small molecules is achieved. In this stage, toxic compounds might be generated, and therefore only biostable biocompatible by-products are the acceptable degradation process products.

The concept of biocompatibility is very important and is acknowledged in medicine and pharmacology. As far as the outdoor environment is concerned, it is not defined in a similar way. The final stage of degradation is multiple, meaning that it consists of mineralization and also biomass formation with residual material.

As a result, the scheme describes the need for specific terms to distinguish these different stages and also distinguish the particularities of the different sections of human activity that are important. Another basic discussion has to be made to identify the possible routes leading from the device to the ultimate stage, which is named mineralization biomass formation.

The two main routes to degrade a polymeric device up to mineralization and biomass formation are possible that are shown in Fig. 14.

The left-handside route related the attack of the device or compound that is followed by an enzymatic process of the degradation products through biochemistry. In this route, the presence of proper enzymes and thus of specific cells under viable conditions (such as

**Figure 14.** The two general routes leading to ultimate degradation and bio-assimilation [27]

atmosphere, water, nutrients, etc.) is needed. No life-allowing conditions means that there is not any degradation happening.

The right-hand-side route has a different way in which breakdown of the device and macro‐ molecule depends on some chemical processes, and the elimination of the generated small molecules proceeds dominantly through biochemical pathways. In this type, the reagents (light, water, heat, etc.) are needed to trigger the degradation. In fact, no-triggering phenom‐ enon means that there isn't any degradation happening [16].

#### **5. The composting process and methods [26-29]**

Another stage is the process of macromolecule breakdown to some biostable small molecules is achieved. In this stage, toxic compounds might be generated, and therefore only biostable

The concept of biocompatibility is very important and is acknowledged in medicine and pharmacology. As far as the outdoor environment is concerned, it is not defined in a similar way. The final stage of degradation is multiple, meaning that it consists of mineralization and

As a result, the scheme describes the need for specific terms to distinguish these different stages and also distinguish the particularities of the different sections of human activity that are important. Another basic discussion has to be made to identify the possible routes leading from the device to the ultimate stage, which is named mineralization biomass formation.

The two main routes to degrade a polymeric device up to mineralization and biomass

The left-handside route related the attack of the device or compound that is followed by an enzymatic process of the degradation products through biochemistry. In this route, the presence of proper enzymes and thus of specific cells under viable conditions (such as

biocompatible by-products are the acceptable degradation process products.

also biomass formation with residual material.

**Figure 13.** The various levels of degradation for a polymer device

80 Recycling Materials Based on Environmentally Friendly Techniques

formation are possible that are shown in Fig. 14.

As nature's way of recycling, composting is the process of transforming organic material into solid-like product that is called humus. This process breaks down the organic materials by using microorganisms such as bacteria and fungi. Having a continuous supply of food (organics), water, and oxygen, the best gen is critical to obtain the best results. In addition, the other important factor to make the process work is managing the composting material's temperature.

Making compost is viable from the most organic by-products [18]. Feedstocks such as poultry, hog, and cattle manures, food processing wastes, sewage sludge, municipal leaves, brush and grass clipping, and sawdust are the most common [19].

The main composted waste types are:


During composting process, organic matter has broken down by microorganisms consequent‐ ly carbon dioxide, heat, water and compost are produced:

( ) Organic matter + microorganisms + O air H O+ CO + Compost + heat 2 22 ®

Although nature compost is the end product of the stabilization stage, fresh compost is an intermediate product of the thermophilic stage.

The raw materials and the factors that affect the progress of the process are the main factors that affect compost characteristics.

Depending on the quality produced and product quality, composts have various applications. For instance, high-quality compost is being used in horticulture, agriculture, landscaping, and home gardening. The medium quality is used in erosion control and roadside landscaping.

Even low-quality compost in land reclamation projects can be used as a landfill coverer. There are three basic types of centralized composting processes:

	- **Low-tech**
		- **◦** Windrow
	- **Mid-tech**
		- **◦** Aerated static pile

The main composted waste types are: **•** Green waste: park and garden waste

82 Recycling Materials Based on Environmentally Friendly Techniques

**•** Slurries and manure from husbandry

ly carbon dioxide, heat, water and compost are produced:

are three basic types of centralized composting processes:

important composting systems are titles as follows [21]:

intermediate product of the thermophilic stage.

that affect compost characteristics.

mechanically agitated.

method, pile is not turned.

**• Low-tech**

**• Mid-tech**

**◦** Windrow

**◦** Aerated static pile

**•** Biodegradable waste stream from manufacturing (food processing wastes, wood wastes)

During composting process, organic matter has broken down by microorganisms consequent‐

( ) Organic matter + microorganisms + O air H O+ CO + Compost + heat 2 22 ®

Although nature compost is the end product of the stabilization stage, fresh compost is an

The raw materials and the factors that affect the progress of the process are the main factors

Depending on the quality produced and product quality, composts have various applications. For instance, high-quality compost is being used in horticulture, agriculture, landscaping, and home gardening. The medium quality is used in erosion control and roadside landscaping. Even low-quality compost in land reclamation projects can be used as a landfill coverer. There

**1. In-vessel method:** in this process, the organic material is composted inside a silo, a drum, an agitated bed in covered or open channel, in a batch container or other structure. The process conditions are clearly monitored and controlled; also the material is aerated and

**2. Aerated static pile method**: in this method compostable materials form into large piles, which are aerated by drawing the air through the pile or forcing air out through it. In this

**3. Windrow method:** In this method, compostable material is formed into elongated piles, known as windrows. The windrows are turned on a regular basis mechanically. Therefore

**•** Biowaste: food waste

**•** Municipal solid waste

**•** Sewage sludge


In high-tech "in-vessel "composting systems, enclosed rigid structures or vessels are used to contain the material undergoing biological processing [22]. For monitoring of the process, process control systems are used to evaluate biological activity by using probes that measure the air temperature and the concentration of O2 and/or CO2. Precise determination of the status of the degradation process is possible via monitoring the concentration of evolved gases.

In most plants, an air treatment unit for limiting of the emission of particulate and gaseous pollutants into the atmosphere is also included.

In-vessel systems divide into two main categories: vertical and horizontal bioreactors. Vertical reactor has cylindrical structure or container and composed of concrete or steel, having a volume of about 100 to more than 2, 000 m3 [30]. The material is loaded at the top and is extracted from the bottom continuously. Forcing air from the bottom of the reactor by means of a centrifugal blower is carried out, countercurrent to the flow of the composting material and caused to a suitable aeration. Vertical systems have been almost replaced by horizontal bioreactors. In horizontal systems, forced aeration is used to maintain the biomass at the necessary aerobic conditions, usually combined with mechanical turning. Continuous or discontinuous working cycle can be used. Composting needs special conditions, particularly of temperature, moisture, pH, aeration, and carbon-to-nitrogen (C/N) ratio, related to optimum biological activity in the various stages of the process [17].

Degradation of the waste in compost carried out in three phases [17, 23]:


The mesophilic phase, according to the ASTM standard [3], is the phase of composting that occurs from 20 to 45; the thermophilic phase is the phase in the composting process that occurs from 45 to 75 which associated with certain colonies of microorganisms that have a high rate of decomposition.

#### **5.1. The first mesophilic phase [23]**

In the first stage of composting, mesophilic bacteria and fungi degrade degradable compounds of organic matter, such as monosaccharide, starch, and lipids easily due to their solubility. Organic acids are produced by bacteria, and the pH decreases to 5–5.5.

As heat is released from exothermal degradation reactions, the temperature starts to rise spontaneously. Also, the degradation of proteins leads to release of ammonia, and the pH rises from 8 to 9 rapidly. A few hours to a few days is needed to end this phase.

#### **5.2. Thermophilic phase [23]**

The thermophilic phase starts when the temperature reaches about 40 °C. The degrada‐ tion rate of the waste increases as thermophilic bacteria and fungi take over. If the temperature reaches over 55–60 °C, microbial activity and diversity greatly decrease. The pH stabilizes to a neutral level after peak heating. This phase can last from a few days to several months.

#### **5.3. Cooling and maturation phase [23]**

When the easily degradable carbon sources have been consumed, the compost starts to cool. After cooling, stable compost is obtained. Then, mesophilic bacteria and fungi reappear, and finally the maturation phase follows. However, most of the species are different from the species of the first mesophilic phase. Actinomycetes often grow during this phase extensively, and a wide range of macroorganisms and some protists are usually present. The biological processes are now slow, but the compost is further converted to humus (humified) and becomes mature.

The required time for the phases depends on the composition of the organic matter as well as the efficiency of the process, which can be determined based on oxygen consumption during the process.

#### **6. Compostable polymers**

"Compostable polymers" were first introduced commercially in the 1980s and were also named "biodegradable polymers." These materials that are the first-generation biodegradable products were made from a conventional polymer, usually polyolefin (e.g., polyethylene) mixed with starch or other organic substances. When starch was eaten by microorganisms, the products were broken down, leaving small fragments of polyolefins. In 1994, Narayan wrote: "The U.S. biodegradables industry fumbled at the beginning by introducing starch filled (6-15%) polyolefins as true biodegradable materials"[28].

These were only biodisintegradable at the best conditions and not completely biodegradable.

According to ISO/DIS 17088 and ASTM D 6400 standards, definitions of compost and com‐ postability are as follows:

**Compost:** Organic soil conditioner obtained by biodegradation of a mixture consisting principally of vegetable residues, occasionally with other organic material and having a limited mineral content

**Composting:** The autothermic and thermophilic biological decomposition of biowaste (organic waste) in the presence of oxygen and under controlled conditions by the action of microorganisms and microorganisms in order to produce compost

**Compostable polymer** : A polymer that undergoes degradation by biological processes during composting to yield CO2, water, inorganic compounds, and biomass at a rate consistent with other known compostable materials and leaves no visible, distinguishable, or toxic residue

**Figure 15.** Classification of compostable polymers

As heat is released from exothermal degradation reactions, the temperature starts to rise spontaneously. Also, the degradation of proteins leads to release of ammonia, and the pH rises

The thermophilic phase starts when the temperature reaches about 40 °C. The degrada‐ tion rate of the waste increases as thermophilic bacteria and fungi take over. If the temperature reaches over 55–60 °C, microbial activity and diversity greatly decrease. The pH stabilizes to a neutral level after peak heating. This phase can last from a few days to

When the easily degradable carbon sources have been consumed, the compost starts to cool. After cooling, stable compost is obtained. Then, mesophilic bacteria and fungi reappear, and finally the maturation phase follows. However, most of the species are different from the species of the first mesophilic phase. Actinomycetes often grow during this phase extensively, and a wide range of macroorganisms and some protists are usually present. The biological processes are now slow, but the compost is further converted to humus (humified) and

The required time for the phases depends on the composition of the organic matter as well as the efficiency of the process, which can be determined based on oxygen consumption during

"Compostable polymers" were first introduced commercially in the 1980s and were also named "biodegradable polymers." These materials that are the first-generation biodegradable products were made from a conventional polymer, usually polyolefin (e.g., polyethylene) mixed with starch or other organic substances. When starch was eaten by microorganisms, the products were broken down, leaving small fragments of polyolefins. In 1994, Narayan wrote: "The U.S. biodegradables industry fumbled at the beginning by introducing starch filled

These were only biodisintegradable at the best conditions and not completely biodegradable.

According to ISO/DIS 17088 and ASTM D 6400 standards, definitions of compost and com‐

**Compost:** Organic soil conditioner obtained by biodegradation of a mixture consisting principally of vegetable residues, occasionally with other organic material and having a limited

from 8 to 9 rapidly. A few hours to a few days is needed to end this phase.

**5.2. Thermophilic phase [23]**

**5.3. Cooling and maturation phase [23]**

84 Recycling Materials Based on Environmentally Friendly Techniques

several months.

becomes mature.

**6. Compostable polymers**

postability are as follows:

mineral content

(6-15%) polyolefins as true biodegradable materials"[28].

the process.

**Disintegration:** The physical breakdown of a material into very small fragments. Put briefly, the requirements a material must satisfy to be termed "compostable" include mineralization (i.e., biodegradation to carbon dioxide, water, and biomass), disintegration into a composting system, and completion of its biodegradation during the end use of the compost, which, moreover, must meet relevant quality criteria, e.g., no ecotoxicity. The satisfaction of require‐ ments should be proven by standardized test methods. These requirements and test methods are described in Section 7.

#### **6.1. Classification of compostable polymers**

Compostable polymers can be divided according to the source of origin or preparation method (Fig. 15).

On the basis of origin, compostable polymers are derived from renewable and petrochemical resources.

*6.1.1. Biodegradable polymers from renewable resources include:*


There are three principal ways to produce polymers from renewable resources, i.e., bio-based polymers:


In general, on the basis of methods of preparation, compostable polymer materials can be prepared via:

**1.** Conventional synthesis:

Examples: PCL, poly (e-caprolactone) – copolyesters

**•** Polymerization from renewable monomer feedstocks:

Examples: polylactic acid

**2.** Biotechnological route (extraction, fermentation)

Examples: poly(hydroxybutyrate-co-hydroxyvalerate) – PHBV

**3.** Preparation directly from biomass

Examples: plants – starch

**4.** Blending

Examples: Starch-polycaprolactone blends

A method based on blending of biodegradable polymers is very often used in order to improve the properties of compostable polymer materials or to decrease their cost. The various polymers used are both renewable polymers in an extruder in the presence of water or plasticizer [31].

#### *6.1.2. Biodegradable polymers from petrochemical sources include:*


#### *6.1.3. Blends*

*6.1.1. Biodegradable polymers from renewable resources include:*

86 Recycling Materials Based on Environmentally Friendly Techniques

**2.** Polyhydroxyalkanoates: poly(3-hydroxybutyrate) (PHB)

There are three principal ways to produce polymers from renewable resources, i.e., bio-based

**1.** To make use of natural polymers which may be modified but remain intact to a large

**2.** To produce bio-based monomers by fermentation which are then polymerized (e.g.,

**3.** To produce bio-based polymers directly in microorganisms or in genetically modified

In general, on the basis of methods of preparation, compostable polymer materials can be

A method based on blending of biodegradable polymers is very often used in order to improve the properties of compostable polymer materials or to decrease their cost. The various polymers used are both renewable polymers in an extruder in the presence of water or

**1.** Polylactide (PLA)

**4.** Cellulose

**5.** Chitosan

**6.** Proteins

polymers:

prepared via:

**3.** Thermoplastic starch (TPS)

extent (e.g., starch polymers)

crops (polyhydroxyalkanoates)

**3.** Preparation directly from biomass

Examples: Starch-polycaprolactone blends

Examples: PCL, poly (e-caprolactone) – copolyesters

**2.** Biotechnological route (extraction, fermentation)

Examples: poly(hydroxybutyrate-co-hydroxyvalerate) – PHBV

**•** Polymerization from renewable monomer feedstocks:

polylactic acid)

**1.** Conventional synthesis:

Examples: polylactic acid

Examples: plants – starch

**4.** Blending

plasticizer [31].

The blending of biodegradable polymers is one of the strategies adopted in producing compostable polymer materials. Blending is a common practice in polymer science to improve unsatisfactory physical properties of the existing polymer or to decrease cost. By varying the composition and processing of blends, it is possible to manipulate properties. The leading compostable blends are starch-based materials. The aim is to combine the low cost of starch with higher-cost polymers having better physical properties. An example of such material is Mater-Bi manufactured by Novamont [46]. Mater-Bi is prepared by blending starch with other biodegradable polymers in an extruder in the presence of water or plasticizer. Some of Commercially available blends are presented in Table 2.


**Table 2.** Commercially available blends

#### **7. Biocompostables**

Compared to other available options, biocompostable products are an eco-friendly alternative, which can help reduce social and economic inequalities, decrease the impact of our consump‐ tion on the environment, and provide opportunities for creating a better and sustainable planet. In line with this goal, many technical attempts have been made to find a substitute plastic for packaging, compostable polymers, tissue engineering, etc. Several biopolymers have been exploited to develop materials for eco-friendly food packaging. However, there is a limitation on the use of biopolymers due to its usually poor mechanical and barrier proper‐ ties, which may be improved by adding reinforcing compounds or fillers in order to form composites.

Most reinforced materials result in poor matrix–filler interactions, which usually improve with decreasing filler dimensions. The use of fillers with at least one nanoscale dimension (nano‐ particles) produces nanocomposites. By using a variety of building blocks with dimensions in the nanosize region, designing and creating new materials with unprecedented flexibility and improvements in their physical properties is possible.

The ideal biopolymer is of renewable biological origin and biodegradable at the end of its life. Biopolymers include polysaccharides such as cellulose and starch, carbohydrate polymers produced by bacteria and fungi, and animal protein-based biopolymers such as wool, silk, gelatin, and collagen. On the other hand, poly(vinyl alcohol) (PVA), poly(caprolactone) (PCL), and poly(butylene succinate) (PBS) are examples of polymers that have synthetic origin but are biodegradable. Recently, natural renewable products made from starches extracted from corn, potato, tapioca, or other plants and vegetable matter are combined with biodegradable polymers to create products that are compostable or biodegradable and can assist in reducing the carbon footprint impact on the environment. Some product sources can come from recycled fiber from sugarcane, bamboo, wheat, rice, and even switch-grass to be formed into everyday used compostable.

#### **7.1. Nanocomposites for food packaging applications**

Most materials that are being used for food packaging are nondegradable and therefore create environmental problems. Several biopolymers have been taken advantage of to develop materials for eco-friendly food packaging. There have been limitations on the use of biopoly‐ mers due to their poor mechanical and barrier properties. This may be modified by adding some reinforcing compounds, forming composites.

Most reinforced materials present poor matrix–filler interactions, which usually improve with decreasing filler dimensions. To produce nanocomposites, the use of fillers with at least one nanoscale dimension (nanoparticles) is a common method.

Nanoparticles have proportionally larger surface area than their microscale counterparts, which favors the filler–matrix interactions and the performance of the resulting material. Furthermore, nanoparticles can have other functions when added to a polymer, such as increasing of tensile modulus, antimicrobial activity, enzyme immobilization, biosensing, etc. An outline of the main kinds of nanoparticles which have been studied for use in food packaging systems is given, as well as their effects and application. Besides nanoreinforce‐ ments, nanoparticles can have other functions when added to a polymer, such as enzyme immobilization, antimicrobial activity, biosensing, etc.

Some of the nanoparticles are:


a limitation on the use of biopolymers due to its usually poor mechanical and barrier proper‐ ties, which may be improved by adding reinforcing compounds or fillers in order to form

Most reinforced materials result in poor matrix–filler interactions, which usually improve with decreasing filler dimensions. The use of fillers with at least one nanoscale dimension (nano‐ particles) produces nanocomposites. By using a variety of building blocks with dimensions in the nanosize region, designing and creating new materials with unprecedented flexibility and

The ideal biopolymer is of renewable biological origin and biodegradable at the end of its life. Biopolymers include polysaccharides such as cellulose and starch, carbohydrate polymers produced by bacteria and fungi, and animal protein-based biopolymers such as wool, silk, gelatin, and collagen. On the other hand, poly(vinyl alcohol) (PVA), poly(caprolactone) (PCL), and poly(butylene succinate) (PBS) are examples of polymers that have synthetic origin but are biodegradable. Recently, natural renewable products made from starches extracted from corn, potato, tapioca, or other plants and vegetable matter are combined with biodegradable polymers to create products that are compostable or biodegradable and can assist in reducing the carbon footprint impact on the environment. Some product sources can come from recycled fiber from sugarcane, bamboo, wheat, rice, and even switch-grass to be formed into everyday

Most materials that are being used for food packaging are nondegradable and therefore create environmental problems. Several biopolymers have been taken advantage of to develop materials for eco-friendly food packaging. There have been limitations on the use of biopoly‐ mers due to their poor mechanical and barrier properties. This may be modified by adding

Most reinforced materials present poor matrix–filler interactions, which usually improve with decreasing filler dimensions. To produce nanocomposites, the use of fillers with at least one

Nanoparticles have proportionally larger surface area than their microscale counterparts, which favors the filler–matrix interactions and the performance of the resulting material. Furthermore, nanoparticles can have other functions when added to a polymer, such as increasing of tensile modulus, antimicrobial activity, enzyme immobilization, biosensing, etc. An outline of the main kinds of nanoparticles which have been studied for use in food packaging systems is given, as well as their effects and application. Besides nanoreinforce‐ ments, nanoparticles can have other functions when added to a polymer, such as enzyme

improvements in their physical properties is possible.

88 Recycling Materials Based on Environmentally Friendly Techniques

**7.1. Nanocomposites for food packaging applications**

some reinforcing compounds, forming composites.

nanoscale dimension (nanoparticles) is a common method.

immobilization, antimicrobial activity, biosensing, etc.

Some of the nanoparticles are:

**•** Cellulose-based nanoreinforcements

**•** Clays and silicates

composites.

used compostable.


The layered silicates which are commonly used in nanocomposites consist of two-dimensional layers that are 1 nm thick and several microns long depending on the used particular silicate. The presence of these types of reinforcing agents in polymer formulations increases the tortuosity of the diffusive path for a permeant molecule (Fig. 16) and provides good barrier properties [24].

**Figure 16.** Tortuous path of a permeant in a clay nanocomposite [32]

Biodegradable all-cellulosic composite nonwoven materials composed of cotton and kenaf or cotton and bagasse have been developed by Zhang [33].

Composting causes significant reduction in the use of chemical fertilizer, plant diseases, water consumption, erosion, etc. It also increases soil quality, production yield, and product quality.

Some technologies exist, but investment cost may be a problem and preselecting is necessary. The composting method depends on waste composition.

#### **8. Testing methods for evaluation of biodegradation**

To determine biological action on man-made materials for various classes, test methods have been available for many years. Recently, the evaluation of the degradability of chemicals in the environment, specifically in wastewater, as one important aspect of the ecological impact of a compound has become significant when attempting to bring new chemical products to the marketplace. For this means, many standardized tests have been prepared for different environments, using different analytical methods [34]. An overview of existing international standards in this area is provided in Table 3. In principle, tests can be subdivided into three categories: field tests, simulation tests, and laboratory tests. Fossil fuels will finish; therefore we require new resources for energy and polymers and effective waste management strategies (according to AS ISO 14855).


**Table 3.** Standard test methods for biocorrosion phenomena on plastics

#### **8.1. General principles in testing biodegradable plastics**

Testing degradation phenomena of plastics in the environment has an overall problem regarding the type of tests to be implemented and the results that can be obtained. The guiding principle is that tests can be subdivided into three categories: field tests, simulation tests, and laboratory tests (Fig. 17).

While field tests, such as burying plastics samples in soil, placing them in lakes or rivers, or performing a full-scale composting process with the biodegradable plastic, represent the ideal practical environmental conditions, several serious disadvantages exist regarding these types of tests.

Environmental conditions such as temperature, pH, or humidity cannot be controlled very well. Also, the analytical opportunities to monitor the degradation process are limited. In most cases, evaluating visible changes on the polymer specimen or perhaps determining disinte‐ gration by measuring weight loss is the only solution.

However, if the material breaks into small fragments that must be quantitatively recovered from the compost, soil, or water, the latter approach can lead to a problem. The analysis of residues and intermediates is complicated by the unspecified and complex environment. The pure physical disintegration of a plastic is not known as biodegradation; therefore, these tests alone can never prove whether a material is biodegradable or not. Various simulation tests, as an alternative to field tests, have been used to measure the biodegradation of plastics in the laboratory.

Compostable Polymers and Nanocomposites — A Big Chance for Planet Earth http://dx.doi.org/10.5772/59398 91

**Figure 17.** Schematic overview on tests for biodegradable plastics

standards in this area is provided in Table 3. In principle, tests can be subdivided into three categories: field tests, simulation tests, and laboratory tests. Fossil fuels will finish; therefore we require new resources for energy and polymers and effective waste management strategies

Testing degradation phenomena of plastics in the environment has an overall problem regarding the type of tests to be implemented and the results that can be obtained. The guiding principle is that tests can be subdivided into three categories: field tests, simulation tests, and

While field tests, such as burying plastics samples in soil, placing them in lakes or rivers, or performing a full-scale composting process with the biodegradable plastic, represent the ideal practical environmental conditions, several serious disadvantages exist regarding these types

Environmental conditions such as temperature, pH, or humidity cannot be controlled very well. Also, the analytical opportunities to monitor the degradation process are limited. In most cases, evaluating visible changes on the polymer specimen or perhaps determining disinte‐

However, if the material breaks into small fragments that must be quantitatively recovered from the compost, soil, or water, the latter approach can lead to a problem. The analysis of residues and intermediates is complicated by the unspecified and complex environment. The pure physical disintegration of a plastic is not known as biodegradation; therefore, these tests alone can never prove whether a material is biodegradable or not. Various simulation tests, as an alternative to field tests, have been used to measure the biodegradation of plastics in the

(according to AS ISO 14855).

90 Recycling Materials Based on Environmentally Friendly Techniques

laboratory tests (Fig. 17).

of tests.

laboratory.

**Table 3.** Standard test methods for biocorrosion phenomena on plastics

**8.1. General principles in testing biodegradable plastics**

gration by measuring weight loss is the only solution.

**Figure 18.** Comparison of the enzymatic degradation of the polyester poly(tetramethylene adipate). With a lipase from pseudomonas sp.

In this case, the degradation might take place in compost, seawater, or soil placed in a controlled reactor in a laboratory. However, the environment is still close to the field test situation; the external parameters such as temperature or pH or humidity, etc., can be con‐ trolled and adjusted; also the analytical tools available are better than would be used for some important tests such as field tests, for example, for analysis of residues and intermediates and determination of O2 consumption or CO2 evolution.

Important tests include the soil burial test [35], controlled composting test [36-38], test simulating landfills [25, 39], and aqueous aquarium tests [40].

Occasionally, nutrients are added to increase the microbial activity and accelerate degradation that results in reduction of the time taken to conduct the tests.

Tests which are the most reproducible biodegradation tests are the laboratory tests, in which defined media are used and immunized with a mixed microbial population (from waste water) or individual microbial strains that may have been screened especially for a special polymer.

In the abovementioned tests, which may be optimized for the particularly used microorgan‐ isms' activity, polymers often show higher degradation rate than natural conditions.

During studying the basic mechanisms of polymer biodegradation, higher degradation rate can be considered as an advantage itself, but in laboratory tests, it is only possible to obtain limited conclusions on the absolute degradation rate of plastics in a natural environment. However, these tests are used to a great extent for many systematic investigations. Attempting to use more controlled and reproducible degradation tests involves using of systems where only those extracellular enzymes are present. These enzymes are used to depolymerize a particular group of polymers. This method, compared to weight loss measurements, cannot be used to prove biodegradation in terms of metabolism by a microorganism, but the system is valuable when used a lipase from Pseudomonas sp. for a polymer film and polymer nanoparticles at 40 °C and pH 7. Figure 18 shows an enzymatic degradation of a polyester poly(tetramethylene adipate) with a lipase. In the mentioned test, degradation is expressed as percentage of cleaved ester bonds. The highest ester cleavage of about 40 % results from the dissolution of low-molecular-weight ester groups that are not accessible to attack by the lipase [16, 41].

#### **8.2. Aerobic biodegradation testing**

This test method estimates the compostability of a plastic sample by measuring the amount of carbon dioxide developed over time and the degree of disintegration of the plastic at the outcome.

Samples and mature compost are mixed and tested for a period of six months (according to AS ISO 14855).

According to test method, the compost–sample mix is contained in 3 L glass jars that are called bioreactors and heated up to 58±2 °C inside a water bath. The mentioned bioreactors which are aerated continuously and have their contents mixed routinely are hydrated to maintain a favorable composting environment. All samples are assessed in triplicate against cellulose powder. For passing the biodegradation test, the sample must produce enough CO2 to theoretically degrade by more than 90 % w/w in total (or percentage degradation normalized relative to the degradation of the positive reference) in a period of six months. Figure 19 shows apparatus for aerobic biodegradation testing.

**Figure 19.** Aerobic biodegradation testing

#### *8.2.1. Disintegration testing*

important tests such as field tests, for example, for analysis of residues and intermediates and

Important tests include the soil burial test [35], controlled composting test [36-38], test

Occasionally, nutrients are added to increase the microbial activity and accelerate degradation

Tests which are the most reproducible biodegradation tests are the laboratory tests, in which defined media are used and immunized with a mixed microbial population (from waste water) or individual microbial strains that may have been screened especially for a special polymer. In the abovementioned tests, which may be optimized for the particularly used microorgan‐

During studying the basic mechanisms of polymer biodegradation, higher degradation rate can be considered as an advantage itself, but in laboratory tests, it is only possible to obtain limited conclusions on the absolute degradation rate of plastics in a natural environment. However, these tests are used to a great extent for many systematic investigations. Attempting to use more controlled and reproducible degradation tests involves using of systems where only those extracellular enzymes are present. These enzymes are used to depolymerize a particular group of polymers. This method, compared to weight loss measurements, cannot be used to prove biodegradation in terms of metabolism by a microorganism, but the system is valuable when used a lipase from Pseudomonas sp. for a polymer film and polymer nanoparticles at 40 °C and pH 7. Figure 18 shows an enzymatic degradation of a polyester poly(tetramethylene adipate) with a lipase. In the mentioned test, degradation is expressed as percentage of cleaved ester bonds. The highest ester cleavage of about 40 % results from the dissolution of low-molecular-weight ester groups that are not accessible to attack by the lipase

This test method estimates the compostability of a plastic sample by measuring the amount of carbon dioxide developed over time and the degree of disintegration of the plastic at the

Samples and mature compost are mixed and tested for a period of six months (according to

According to test method, the compost–sample mix is contained in 3 L glass jars that are called bioreactors and heated up to 58±2 °C inside a water bath. The mentioned bioreactors which are aerated continuously and have their contents mixed routinely are hydrated to maintain a favorable composting environment. All samples are assessed in triplicate against cellulose powder. For passing the biodegradation test, the sample must produce enough CO2 to theoretically degrade by more than 90 % w/w in total (or percentage degradation normalized relative to the degradation of the positive reference) in a period of six months. Figure 19 shows

isms' activity, polymers often show higher degradation rate than natural conditions.

determination of O2 consumption or CO2 evolution.

92 Recycling Materials Based on Environmentally Friendly Techniques

[16, 41].

outcome.

AS ISO 14855).

**8.2. Aerobic biodegradation testing**

apparatus for aerobic biodegradation testing.

simulating landfills [25, 39], and aqueous aquarium tests [40].

that results in reduction of the time taken to conduct the tests.

The disintegration test is a pilot-scale aerobic composting test. In this test, an industrial composting process is simulated in a 200 Liter insulated composting bin. The compost is consisted of organic waste that should cause self-heating during its juvenile stages which is similar to full-scale composting process. Temperature of the compost, composition of exhaust gas, and pH and moisture are monitored routinely until the test is terminated at the end of 12 weeks. The obtained results must satisfy the validation requirements mentioned in a standard test method. Plastic fragmentation in an aerobic composting environment according to AS ISO is shown in Figure 20.

The bin's contents are turned manually at certain time intervals to maintain a uniform test environment. The test specimens can be visually evaluated during the test. At the end of 12 weeks, the remaining specimen fragments are retrieved, sized, and weighed, relative to the initial sample weight. By the test, degree of disintegration achieved can be determined. To pass disintegration testing, the sample must disintegrate or physically break down to a fragment size less than 2 mm, more than 90 % w/w after 12 weeks. All samples are tested in duplicate.

**Figure 20.** Disintegration barrels used to assess plastic fragmentation in an aerobic composting environment according to AS ISO

**Figure 21.** Typical growth seen in radish, seedlings bean during 14-day higher plant

**Figure 22.** Photo of an earthworm ecotoxicity test setup ecotoxicity testing mung

#### **9. Regulation and voluntary standards**

**Figure 20.** Disintegration barrels used to assess plastic fragmentation in an aerobic composting environment according

**Figure 21.** Typical growth seen in radish, seedlings bean during 14-day higher plant

to AS ISO

94 Recycling Materials Based on Environmentally Friendly Techniques

In the USA, two guidelines named EPA Class A and B were developed to manage the proc‐ essing and beneficial reuse of sludge or mud, also called biosolids, following the US EPA ban of ocean dumping. Now, in 26 American states, composts are required to be processed to control for vector and pathogen according to these federal protocols, even though the appli‐ cation to non-sludge materials has not been tested scientifically. As an example, green waste composts at higher rates than sludge compost were used. UK guidelines regarding compost quality also exist which is common in Canadian, Australian, and the various European states. Some compost manufacturers participate in a testing program in the USA called the US Composting Council (USCC) that is offered by a private lobbying organization. In order to promote composting of disposable diapers, the USCC was established in 1991 by Procter & Gamble, following state forces to ban diapers in landfills, which caused a national uproar. Since composting diapers was not proven scientifically to be possible, ultimately the idea was not considered as a good idea.Therefore, composting emphasized to recycle organic wastes that were previously destined for landfills. In America, there are no legal quality standards, but a seal called "Seal of Testing Assurance" (also called "STA") has been sold by the USCC. By paying a high cost, the applicant may use the USCC logo on products, agreeing to volunteer to customers a current laboratory analysis that includes parameters such as respiration rate, nutrients, pH, salt content, and limited other indicators. However that the STA program is not ISO approved, and STA is a financially beneficial activity for the private USCC, which is an organization that discloses its books earned and benefits \$65, 000 from STA fees in 2009. Existence some argue about the STA program means that EPA or USDA does not regulate composts. Tables 4 and 5 show titles of some important standards and definitions used in correlation with biodegradable plastics, respectively.

Coexistence of both biotic and nonbiotic processes, polymer degradation mechanism could also be referred to environmental degradation not only to environmental factors influence the polymer to be degraded, but they also have a influence on the activity of the different micro‐ organisms and microbial population. Factors such as humidity, temperature, salinity, pH, the absence or presence of oxygen, and supply of different nutrients are important effects on the microbial degradation of polymers and should be kept in mind when the biodegradability of plastics is tested. A standard evaluation of biodegradable polymers should always be based on definitions and what biodegradation with regard to polymers actually means. International and national standardization organizations have published several different definitions.


**Table 4.** Titles of some important standards


**Table 5.** Definitions used in correlation with biodegradable plastics

absence or presence of oxygen, and supply of different nutrients are important effects on the microbial degradation of polymers and should be kept in mind when the biodegradability of plastics is tested. A standard evaluation of biodegradable polymers should always be based on definitions and what biodegradation with regard to polymers actually means. International and national standardization organizations have published several different definitions.

96 Recycling Materials Based on Environmentally Friendly Techniques

**Table 4.** Titles of some important standards

#### **9.1. Testing methods**

In order to determine biological action on man-made materials, test methods have been available for quite a long time for different classes of materials. Recently, the evaluation of the degradability of chemicals in the environment, specifically in waste water, as an important aspect of the ecological impact of a compound has become very significant when efforts are being made to present to the marketplace a new chemical product. As a result, numerous standard tests for different environments have been developed using various analytical methods [34]. Table 6 shows an overview of some international standards in this area. In order to evaluate the influence of microorganisms on polymer, test methods have been initiated even before biodegradable plastics were first developed. While conventional plastics are relatively resistant against environmental influences, at some point, microorganisms can attack the plastics to a certain extent and create unwanted changes in the material properties, e.g., in the color or in mechanical properties such as flexibility or mechanical strength [35].


**Table 6.** Standard test methods for biocorrosion phenomena on plastics

While this wide range of degradation tests was already available, it was necessary to develop special test methods when working with biodegradable plastics.

As it could be understood from the listed standards in Table 6, special aspects of plastics materials could not be considered. Regarding the biocorrosion phenomena, the subject of whether or not that a plastic is degraded is not the concern, but it is important that whether minor chemical changes in the polymers (e.g., extraction of plasticizer, oxidation, etc.) caused to changes in the material properties. Evaluation of low-molecular-weight substances was developed specifically for biodegradable plastics during the past decade or so (Itvaara and Vikman, 1996). However, they have been tried to adapt to specific environments in which biodegradable plastics might be degraded. Furthermore, these methods consider the fact that plastics have a complex structure and are degraded by a heterogeneous surface mechanism mainly. Table 7 shows standard test methods used in evaluation of chemicals biodegradability.


**9.1. Testing methods**

98 Recycling Materials Based on Environmentally Friendly Techniques

In order to determine biological action on man-made materials, test methods have been available for quite a long time for different classes of materials. Recently, the evaluation of the degradability of chemicals in the environment, specifically in waste water, as an important aspect of the ecological impact of a compound has become very significant when efforts are being made to present to the marketplace a new chemical product. As a result, numerous standard tests for different environments have been developed using various analytical methods [34]. Table 6 shows an overview of some international standards in this area. In order to evaluate the influence of microorganisms on polymer, test methods have been initiated even before biodegradable plastics were first developed. While conventional plastics are relatively resistant against environmental influences, at some point, microorganisms can attack the plastics to a certain extent and create unwanted changes in the material properties, e.g., in the

color or in mechanical properties such as flexibility or mechanical strength [35].

While this wide range of degradation tests was already available, it was necessary to develop

As it could be understood from the listed standards in Table 6, special aspects of plastics materials could not be considered. Regarding the biocorrosion phenomena, the subject of whether or not that a plastic is degraded is not the concern, but it is important that whether minor chemical changes in the polymers (e.g., extraction of plasticizer, oxidation, etc.) caused to changes in the material properties. Evaluation of low-molecular-weight substances was developed specifically for biodegradable plastics during the past decade or so (Itvaara and Vikman, 1996). However, they have been tried to adapt to specific environments in which biodegradable plastics might be degraded. Furthermore, these methods consider the fact that plastics have a complex structure and are degraded by a heterogeneous surface mechanism mainly. Table 7 shows standard test methods used in evaluation of chemicals biodegradability.

**Table 6.** Standard test methods for biocorrosion phenomena on plastics

special test methods when working with biodegradable plastics.


**Table 7.** Standard test methods for biodegradability of chemicals

#### **10. Conclusion**

Various contaminants into natural environments that have resulted in instability, disorder, harm, or discomfort to an ecosystem is known as pollution and includes different forms such as air, soil, water, sound, etc. Reducing the amount of solid waste in landfills and the addition of nutrient-rich organic matter are the help that composting gives to the Earth. Polymers, composites and nanocomposites made of major chemicals that are highly toxic and pose a serious threat to all living species on the planet Earth. The earth cannot digest these materials and leads to serious damage to the environment during their production and disposal process.

Composting of composites and nanocomposites based on bio-based polymers used in various applications is an important solution to reduce the amount of solid waste in landfills or any other polluted area.

Which way must be chosen to save our planet: the management of packaging and packaging waste's, use of combustible packaging waste in order to generate energy by completely burning the substance or changing them to compost?

Composts improve soil quality, assist plant growth, increase water holding capacity, store carbon in the soil, and reduce the need for chemical fertilizer and pesticides. "Compostable polymer" undergoes degradation by biological processes during composting to yield CO2, water, inorganic compounds, and biomass at a rate consistent with other known compostable materials and leaves no visible, distinguishable, or toxic residue.

Nanoparticles can have other functions when added to a polymer, such as increasing of tensile modulus, antimicrobial activity, enzyme immobilization, biosensing, etc. An outline of the main kinds of nanoparticles which have been studied for use in food packaging systems is given, as well as their effects and application.

Testing degradation phenomena of compostable polymers and nanocomposites in the environment has an overall problem regarding the type of tests to be implemented and the results that can be obtained. The guiding principle is that tests can be subdivided into three categories: field tests, simulation tests, and laboratory tests. Important tests include the soil burial test, controlled composting test, test simulating landfills, and aqueous aquarium tests.

There are some regulation and voluntary standards such as EPA Class A and B tests in USA, UK guidelines regarding compost quality also exist which is common in European Union, Canadian, Australian in the world.

"Let us save our environment from polymer pollution to make it a better environment for the future" To do so, compostable polymers and nanocomposites are a big chance for planet Earth.

#### **Author details**

**Table 7.** Standard test methods for biodegradability of chemicals

100 Recycling Materials Based on Environmentally Friendly Techniques

Various contaminants into natural environments that have resulted in instability, disorder, harm, or discomfort to an ecosystem is known as pollution and includes different forms such

**10. Conclusion**

Gity Mir Mohamad Sadeghi1\* and Sayaf Mahsa2

\*Address all correspondence to: gsadeghi@aut.ac.ir

1 Dep. of Polymer Engineering & Color Technology, Amirkabir University of Technology, Tehran, I.R., Iran

2 Dep. of Chemical Engineering Isfahan University of Technology, Isfahan, I.R., Iran

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from: www.ec.europa.eu/environment/waste/studies/pdf/plastics.pdf

[6] Plastics wastes. Available from: http://marketpublishers.com/report

[7] Garbage patches. Available from: http://marinedebris.noaa.gov/info

[11] Compostable polymer materials, ISBN: 978-0-08-045371-2, Ewa rudnik.

[8] Science for environment policy: In-Dept report, Nov. 2011.

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[4] Plastic waste: ecological and human health impacts. Available from: http://ec.euro‐

[5] Mud gal, S., Lyons, L., Bain, J. et al. (2010) Plastic waste in the environment. Final Re‐ port for European Commission DG Environment, Bio Intelligence Service. Available

[9] Shamsi R et al, 2009; Mohammadi et al, 2010 & Mir Mohamad Sadeghi G. et al, 2011.

[10] Zenda, K, Funazukur T, Depolymerization of poly (ethylene terephthalate) in dilute aqueous ammonia solution under hydrothermal conditions. J Chem Technol Biotech‐

[12] Michael Evans's bio. Available from: http://www.banginfo.in/Environment/Plastic‐

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[14] Shamsi R, Mir Mohamad Sadeghi G, Afshar F, Abdouss M. Polym Int. 2009, 58, 22–

[16] Environmentally degradable plastics, Leonadoda Vinci Program: www.ics.trieste.it,

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[18] Cooperband L, The Art and Science of Composting, Uni. Wisconsin-Madison, Center

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102 Recycling Materials Based on Environmentally Friendly Techniques


## **Potential for Introduction of Preservative Treated Wood in Wood Waste Recycling Streams and its Prevention**

Jeffrey J. Morrell

[36] Pagga U, Beimborn DB, Boelens J, De Wilde B, Determination of the aerobic biode‐ gradability of polymeric material in a laboratory controlled by composting test. Che‐

[37] Degli-Innocenti F, Tosin M, Bastioli C, Evaluation of the biodegradation of starch and cellulose under controlled composting conditions. J Env Polym Degrad 1998, 6, 4:197.

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[40] Püchner P, Müller WR, Bartke D, Assessing the biodegradation potential of polymers in screening and long term test systems. J Env Polym Degrad 1995, 3:133–143.

[41] Yoichi Ando, Biodegradability of poly(tetramethylene succinate-co-tetramethylene adipate): I. Enzymatic hydrolysis. Polym Degrad Stab 1998, 61, 1:129–137.

mosphere 1995, 31, 4475–4487.

104 Recycling Materials Based on Environmentally Friendly Techniques

4:197–202.

1993, 1:281–291.

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/59327

#### **1. Introduction**

The public desire to reduce, reuse and recycle has led to substantial investments in recycling programs. Metals, paper, plastics and a host of other materials are now recycled, thereby conserving precious landfill space. One particularly important waste diversion is in the area of wood and garden waste [1]. These materials tend to be bulky and, more importantly, contribute to the production of methane as they degrade under anaerobic conditions in the landfill. Many communities now divert this material to be composted, separated and burned for energy production or, if the resource is sufficiently free of contaminants, even used to produce composite wood products. Composting has become especially attractive because this material can be combined with more putrescible wastes such as food compost to produce a very rich composted material.

One aspect of wood recycling operations that is often overlooked is the presence of contami‐ nants in the chipped mixture. Metal fasteners can be removed using magnets, but many other materials wind up in this mixture. One of the more important potential contaminants is preservative treated wood [2,3]. Preservative treated wood is typically impregnated with combinations of heavy metals to provide resistance to biological attack. For decades, the most commonly used preservative for residential applications was chromated copper arsenate (CCA). CCA is no longer used for residual applications, but the replacement systems are primarily copper based including alkaline copper quaternary compound (ACQ) or alkaline copper azole (CA). The U.S. Environmental Protection Agency generally recommends that, wherever possible, treated wood be reused in a similar application. Once this is no longer possible, the wood should be disposed of in a licensed municipal solid waste facility with the appropriate liners and leachate management technology. The EPA specifically prohibits the burning of treated wood except in specially licensed facilities. The most common use of

© 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

combustion for disposal of treated wood is with creosote, although it is technically possible to combust other treated wood products. These activities are generally associated with industrial products such as railroad ties or utility poles.

While industrial products are an important component of the potential treated wood disposal stream, the users of these products are generally aware of the requirements for disposal. However, a large amount of preservative treated wood is employed in residential applications for decking, fencing, and a host of other uses. These products have varying service lives and eventually find their way into the waste stream. As with other treated wood products, the EPA recommends reuse following by landfill disposal for these products at the end of their service lives; however, there are several factors that can make this difficult. First, treated wood in many parts of the country tends to fade and weather as it is exposed to ultraviolet light. In many cases, it is virtually impossible to visually distinguish between treated and non-treated wood once it has weathered. In addition, many homeowners do not know that treated wood needs to be disposed of in a landfill and therefore tend to place this material into their yard recycling container where they already place other woody debris. Finally, there is no specific collection pathway for treated wood products, making them difficult to assemble as a single material.

#### **2. Level of contamination in recycled wood**

The potential for contamination of wood recycling streams was brought to light over a decade ago in Florida. Energy recovery facilities that used mixtures of bagasse and waste wood obtained from construction and demolition landfills as fuel sources discovered that their resulting ash contained very high levels of copper, chromium and arsenic. Further investiga‐ tion revealed that high percentages of wood entering construction and demolition debris (C&D) facilities were treated with CCA. However, the wood had weathered to the extent that it was no longer possible to visually detect this material. The Florida situation is unique in a number of ways. The higher risk of decay in this state means that treated wood represents a much higher percentage of the total volume of wood used. In addition, these more severe exposure conditions lead to a shorter overall service life for a given product. The severe UV exposure conditions typically found in Florida tend to reduce the surface appearance of the material, leading to premature removal of wood that is structurally sound, but has a poor appearance. Florida also has a very limited landfill capacity and, at the time had a number of non-lined C&D facilities. This led to large amounts of materials entering combustion facilities. The occurrence of elevated metal levels stimulated a large research effort at the University of Miami and University of Florida to determine the levels of treated wood entering the recycling stream, and, once it became evident that a substantial volume of treated wood was present, how to rapidly detect it.

Copper based systems are currently the most commonly used wood preservatives, but older wood can also contain chromium and arsenic. The EPA labels associated with these chemicals specifically indicate that disposal of products treated with wood preservatives should be in a lined landfill; however, it can sometimes be difficult to determine if wood that has been subjected to extensive ultraviolet light contains preservative treatment. As a result, there is a risk that treated wood can enter the recycling stream. In the case of woody debris used for biofuels, the presence of metal based preservative can result in air-emissions as well as elevated metal levels in the resulting ash. Inadvertent inclusion of treated wood in composting operations could result in elevated metal levels in the subsequent compost. While this is unlikely to pose a risk to plants, it could lead to difficulties if the materials are marketed as being organic.

combustion for disposal of treated wood is with creosote, although it is technically possible to combust other treated wood products. These activities are generally associated with industrial

While industrial products are an important component of the potential treated wood disposal stream, the users of these products are generally aware of the requirements for disposal. However, a large amount of preservative treated wood is employed in residential applications for decking, fencing, and a host of other uses. These products have varying service lives and eventually find their way into the waste stream. As with other treated wood products, the EPA recommends reuse following by landfill disposal for these products at the end of their service lives; however, there are several factors that can make this difficult. First, treated wood in many parts of the country tends to fade and weather as it is exposed to ultraviolet light. In many cases, it is virtually impossible to visually distinguish between treated and non-treated wood once it has weathered. In addition, many homeowners do not know that treated wood needs to be disposed of in a landfill and therefore tend to place this material into their yard recycling container where they already place other woody debris. Finally, there is no specific collection pathway for treated wood products, making them difficult to assemble as a single material.

The potential for contamination of wood recycling streams was brought to light over a decade ago in Florida. Energy recovery facilities that used mixtures of bagasse and waste wood obtained from construction and demolition landfills as fuel sources discovered that their resulting ash contained very high levels of copper, chromium and arsenic. Further investiga‐ tion revealed that high percentages of wood entering construction and demolition debris (C&D) facilities were treated with CCA. However, the wood had weathered to the extent that it was no longer possible to visually detect this material. The Florida situation is unique in a number of ways. The higher risk of decay in this state means that treated wood represents a much higher percentage of the total volume of wood used. In addition, these more severe exposure conditions lead to a shorter overall service life for a given product. The severe UV exposure conditions typically found in Florida tend to reduce the surface appearance of the material, leading to premature removal of wood that is structurally sound, but has a poor appearance. Florida also has a very limited landfill capacity and, at the time had a number of non-lined C&D facilities. This led to large amounts of materials entering combustion facilities. The occurrence of elevated metal levels stimulated a large research effort at the University of Miami and University of Florida to determine the levels of treated wood entering the recycling stream, and, once it became evident that a substantial volume of treated wood was present,

Copper based systems are currently the most commonly used wood preservatives, but older wood can also contain chromium and arsenic. The EPA labels associated with these chemicals specifically indicate that disposal of products treated with wood preservatives should be in a lined landfill; however, it can sometimes be difficult to determine if wood that has been

products such as railroad ties or utility poles.

106 Recycling Materials Based on Environmentally Friendly Techniques

**2. Level of contamination in recycled wood**

how to rapidly detect it.

In either case, quantifying the amounts of treated wood entering a waste stream can help producers determine the level of risk so that they can develop appropriate mitigation meas‐ ures. This risk is likely to differ regionally because of the differing degrees to which treated wood is employed and the length of time it remains in service. The Pacific Northwest is an excellent area in which to determine treated wood incidence in recycling streams because it has well developed recycling programs and the treated wood has distinctive features that make it easier to detect. In this chapter, we will discuss surveys of treated wood incidence in a wood recycling center over a 10 year period and then discuss possible methods for limiting the incidence of such materials [12].

Surveys were conducted at a recycling facility located near Corvallis, Oregon [4]. The facility is a regional composting and recycling facility that processes over 28,000 metric tons of material per year. The facility receives regular yard waste that includes branches, grass, brush, and seasonal influxes such as leaves and Christmas trees. The facility also accepts wood waste from various sources. These materials were formerly chipped separately with the yard debris being composted and the wood debris going to various facilities for combustion for either steam or electricity. This situation has recently changed as a result of the introduction of generation of food waste composting coupled with changes in wood demand in the surrounding area. The food composting operation has resulted in an increase demand for woody debris as a media for the composting, while lower natural gas prices have sharply curtailed the use of woody biomass for energy production. As a result, nearly all wood entering the facility now ends up in the compost mixture.

Most materials arrive at the facility by commercial haulers, but nearby residents can also drop off materials for a fee. Loads can be inspected at the gate house, but it is not feasible to inspect every load. As a result, it is possible for contaminants to enter the recycling stream. Wood entering the facility is segregated into a separate pile for chipping. Chipping occurs as equipment becomes available and the resulting wood chips are stored until needed for constructing a compost pile. Once the wood is chipped, it is virtually impossible to detect the presence of treated wood.

Detecting treated wood prior to chipping is relatively simple. The wood is normally piled in such a way that the vast majority of the pile is accessible. Treated wood in the Pacific Northwest is much easier to detect because it is generally stained with a brown pigment to makes it appear like western redcedar. In addition, a large percentage of the material is incised. This process drives metal teeth into the wood to improve the depth of preservative treatment. Incision marks are easily seen, even in older wood, making detection of treated wood in a pile relatively simple (Figure 1).

**Figure 1.** Example of wood with incisions that make it relatively easy to detect preservative treated wood in recycling facilities in the Western U.S.

The amount of treated wood has been visually assessed 168 times over the 12 year period [10]. At each time point, the size of the entire pile was estimated. The presence of treated wood of a given dimension in the pile was then visually determined (for example 4 by 4 inches, 2 by 4 inches, etc.) and the length was estimated to the nearest 300 mm. As mentioned, treated wood is readily detected in this part of the United States because of the distinctive brown stain and/ or the presence of incisions. Depending on pile size, visual detection of treated wood is possible 1 to 3 m inward from the outside of the pile. In addition, we estimated the relative proportions of yard debris, pallets, panels, and demolition debris. This latter categorization only began after we had performed for the first 40 observations.

Ideally, wood mass would be used to estimated treated wood proportions, however, this was not possible because of safety issues related to the placement of the materials in a pile. Instead, the lineal footage of each piece of dimension material detected was used to determine overall volume of wood using actual dimensions. Lumber for residential applications was primarily treated with chromated copper arsenate (CCA) until 2003 when this material was withdrawn from the market. Alkaline copper quaternary (ACQ) compound or copper azole (CA) largely replaced CCA for this application [5]. It is not possible to visually distinguish wood treated with these three chemicals because of the brown pigments. The use of a copper indicator also would not help since all three systems contain copper as the primary biocide. For the purpose of determining chemical loading, we assumed that all of the wood had been treated to the American Wood Protection Association Standards ground contact retention for treatment of lumber with any of the water borne materials (6.4 kg/m3 for ACQ or CCA) and that the entire cross section had been treated to that level. Average wood densities were then used to calculate the total amount of metal present in the material [6,7]. This is an extremely conservative approach because wood in this region is difficult to penetrate with preservatives. As a result, somewhere between 40 and 60 % of the cross section is actually preservative treated and not all wood is treated to the higher retention level. However, since we could not visually assess treatment depth or retention, we used the conservative approach. As a result, the estimates of total chemical in the wood were intentionally high.

Pallets, yard debris, and demolition debriswere the most abundant materials detected in piles at the site (Figure 2). The average volume of material present at any given inspection was 338.8 m3 . Pallets were the most abundant manufactured material at the site (39 of 128 times), while yard debris, which include branches and leaves was the most common 68 times [10]. A variety of other materials were also present including panel trim scraps and shingles, but these represented minor volumes compared to the two most common materials. For example, Christmas trees were seasonally abundant, but represented an overall low percentage of the total mass delivered to the site.

**Figure 1.** Example of wood with incisions that make it relatively easy to detect preservative treated wood in recycling

The amount of treated wood has been visually assessed 168 times over the 12 year period [10]. At each time point, the size of the entire pile was estimated. The presence of treated wood of a given dimension in the pile was then visually determined (for example 4 by 4 inches, 2 by 4 inches, etc.) and the length was estimated to the nearest 300 mm. As mentioned, treated wood is readily detected in this part of the United States because of the distinctive brown stain and/ or the presence of incisions. Depending on pile size, visual detection of treated wood is possible 1 to 3 m inward from the outside of the pile. In addition, we estimated the relative proportions of yard debris, pallets, panels, and demolition debris. This latter categorization only began

Ideally, wood mass would be used to estimated treated wood proportions, however, this was not possible because of safety issues related to the placement of the materials in a pile. Instead, the lineal footage of each piece of dimension material detected was used to determine overall volume of wood using actual dimensions. Lumber for residential applications was primarily treated with chromated copper arsenate (CCA) until 2003 when this material was withdrawn from the market. Alkaline copper quaternary (ACQ) compound or copper azole (CA) largely replaced CCA for this application [5]. It is not possible to visually distinguish wood treated with these three chemicals because of the brown pigments. The use of a copper indicator also would not help since all three systems contain copper as the primary biocide. For the purpose of determining chemical loading, we assumed that all of the wood had been treated to the American Wood Protection Association Standards ground contact retention for treatment of

facilities in the Western U.S.

after we had performed for the first 40 observations.

108 Recycling Materials Based on Environmentally Friendly Techniques

**Figure 2.** Frequency of a given woody material being the dominant substrate present at the recycling center (from 10)

Treated wood was present in 155 out of 168 inspections or 92.3 % of the samples (Figure 3). The percentages of treated wood were generally low in the samples, ranging from <0.01 % to 2.0 % of the estimated volume (Figure 4). Levels at or above 1 % were only detected 3 times over the 12 year period. The average volume of treated wood present was 0.15 % over the 12 years. Treated wood levels were > 0.2 % of the volume in 20.5 % of the inspections,while they were between 0.1 and 0.2 % of the volumes in another 16.1 % of the inspections. Treated wood

**Figure 3.** Percentages of treated wood detected in a recycling facility located in Western Oregon as determined by peri‐ od visual surveys over a 12 year period.

**Figure 4.** Frequency of different levels of treated wood in a wood recycling center in Western Oregon assessed over a 10 year period. Values are based upon 112 surveys (from 10).

represented less than 0.1 % of the volume in a majority of inspections (63.4%), indicating that this material was a relatively small proportion of the recycling stream.

#### **3. Implications of treated wood contamination**

These data provide an example of the potential for inadvertent presence of treated wood in the recycling stream and a relatively simple method for assessing the extent. However, it is important to recognize that every site is different. In some cases, the overall volumes of wood in a facility are too great for this approach or the materials are processed directly and not available for inspection. In addition, the proportions of treated wood at this site were relatively low and the treated products were relatively easily detected. Never the less, it is important to develop reliable estimates of the levels of treated wood entering recycling streams. In the cases of materials that are combusted for energy production, excess amounts of treated wood in the feedstock can lead to releases of arsene gases and produce residual ash with excessively high metal contents that can pose a disposal hazard. This becomes quite important in some facilities. For example, previous studies of wood recycling facilities have shown that 5.9 % of volume at a C&D facility in Florida was treated wood [8], while 2.5 % of the wood entering the waste stream in Virginia was treated [9]. The risk can be examined by considering the potential inputs of metals into ash resulting from combustion of the materials. If we used the Oregon facility data indicating that if an average of 0.15 % of the incoming wood was CCA treated, then As, Cr and Cu levels would be 2380,2640 and 1580 ppm in the resulting ash [10]. Cu levels would be much higher if the wood was treated with either alkaline copper azole or alkaline copper quat but no arsenic or chromium would be present. It is important to realize that material from this particular facility was used to supplement other fuel supplies at local wood processing facilities. As a result there is likely to be considerable dilution with non-treated wood so that the resulting ash would not pose a disposal issue. However, the results do illustrate the potential for creating metal contaminated ashes in areas where large amounts of treated wood are employed. For example, if the treated wood levels present in the C & D facility in Florida were used, then As, Cr and Cu levels in the resulting ash would be 92820, 102,960, and 61620 ppm, respectively, and ash disposal would pose a major challenge. It is important to remember that metals do not disappear from compost. Thus, these same metal input levels would be present in any compost. The Oregon facility received 1318.2 metric tons of wood waste in 2013 along with other materials. If we use the 0.15 % treated wood composition figure, this material would result in an input of 28.2 kg of CCA. CCA Type C is composed of 47.5 % chromic acid, 18.5 % copper oxide and 34 % arsenic pentoxide [5]. These elements are expressed on an oxide basis. If we convert the total CCA input to elemental metals, the treated wood would input 6.97 kg of Cr, 4.50 kg of copper and 4.61 kg of arsenic into the system. The facility produced over 58,707,273 kg of compost (wet weight) from all of the inputs. If we use a 50 % moisture content for the compost, then the metal inputs would represent potential increases of 0.119 ppm, 0.077 ppm, and 0.079 ppm for Cr, Cu and As, respectively. Obviously, the potential impacts of such small inputs would be lost within the inherent variability of other material inputs such as the components of the food compost (for example, some seafoods contain elevated levels of arsenic). The results illustrate the minimal impact of treated wood on either combustion or composting of the incoming material at the Oregon site. A comparative operation in Florida where the treated wood input was estimated to be 39 times higher would increase metal levels in the resulting compost by 4.6, 3.0 and 3.1 ppm respectively. There are limited publically available data on metal levels in compost from facilities such as these, but a survey of Florida composting operations suggests that these inputs would not markedly alter the metal levels in the compost [11]. Some Florida soils have extremely low metal levels and these concentrations would certainly have the potential to increase overall soil metal levels if

represented less than 0.1 % of the volume in a majority of inspections (63.4%), indicating that

**Figure 4.** Frequency of different levels of treated wood in a wood recycling center in Western Oregon assessed over a

**Figure 3.** Percentages of treated wood detected in a recycling facility located in Western Oregon as determined by peri‐

These data provide an example of the potential for inadvertent presence of treated wood in the recycling stream and a relatively simple method for assessing the extent. However, it is

this material was a relatively small proportion of the recycling stream.

**3. Implications of treated wood contamination**

10 year period. Values are based upon 112 surveys (from 10).

od visual surveys over a 12 year period.

110 Recycling Materials Based on Environmentally Friendly Techniques

compost were repeatedly used on the same site; however, these inputs would likely be balanced by plant uptakes. It is important to note that these levels would still be well below those found in soils from most other locations in North America.

#### **4. Preventing contamination of recycled wood**

The volumes of treated wood entering the facility we surveyed were 1.9 to 4 % of those found at other sites. Furthermore, the levels have actually declined slightly over the past decade.The reasons for the decline are unclear since the facility made no specific effort to exclude materials. While attempts should be made to divert as much of this material as possible from the recycling stream and into a lined landfill, it is obvious that there is a far greater need to accomplish this at the other sites.

Diverting this material; however, is problematic because most of those disposing treated wood materials are homeowners or small contractors who have little basic knowledge about wood treatments. While end-tags on most treated lumber do warn against burning the product, few read these tags and most of the tags are no longer on the wood at the end of its service life. Thus, recycling facilities need to consider alternative methods. Detection at the recycling center would be ideal because it would eliminate the need for consumers to be aware of proper disposal. However, this approach requires that the material be processed so that every piece of wood can be examined. In the case of the Oregon facility, the chipper is mobile and has a relatively short conveyor system that would make it difficult to assess every piece of wood. Even when assessment is possible, problems arise because of the difficulty in sorting individual samples. A number of approaches have been examined for detecting wood treated with waterborne preservatives which would most likely be present in a recycling stream. As mentioned earlier, metal treated wood in many locations tends to weather to a greyish colour that makes it virtually indistinguishable from weathered non-treated wood. Thus, visual detection is likely to be very inaccurate except where other factors, such as the use of dyes or incising in the western U.S. make the wood more recognizable. Nearly all of these systems are copper-based and there are several very sensitive indicators that might be useful. These indicators would have to be sprayed on all of the wood pieces in order to be used. That would require sizable quantities of indicator and some time for the reaction to become evident. This would make it difficult to apply in an industrial environment. There are similar indicators capable of detecting arsenic but these systems would suffer from the same problems. These indicators would also not be suitable for newer materials entering the waste stream, since arsenic based systems were phased out of the residential market in 2003 and will therefore represent an ever-decreasing percentage of the treated material of potential concern.

Heavy metals can also be detected using x-ray technologies, notably x-ray fluorescent spec‐ troscopy (XRF). XRF is widely used in quality control programs for assessing the amounts of copper, zinc, arsenic and chromium in preservative treated wood. It is fairly sensitive to low levels of metal and preliminary studies indicate that the method even detected residual metals in wood through surface coatings [12, 13]; however, it does use ionizing radiation and most current systems use x-ray tubes that may be somewhat fragile for operations within an industrial environment with a great deal of contamination. These are, however, technical issues that could be overcome if there were sufficient levels of treated wood in a waste stream. At present, routine x-ray screening for the presence of treated wood is probably not feasible or economical given the low value of the resulting compost or biomass chips.

compost were repeatedly used on the same site; however, these inputs would likely be balanced by plant uptakes. It is important to note that these levels would still be well below

The volumes of treated wood entering the facility we surveyed were 1.9 to 4 % of those found at other sites. Furthermore, the levels have actually declined slightly over the past decade.The reasons for the decline are unclear since the facility made no specific effort to exclude materials. While attempts should be made to divert as much of this material as possible from the recycling stream and into a lined landfill, it is obvious that there is a far greater need to accomplish this

Diverting this material; however, is problematic because most of those disposing treated wood materials are homeowners or small contractors who have little basic knowledge about wood treatments. While end-tags on most treated lumber do warn against burning the product, few read these tags and most of the tags are no longer on the wood at the end of its service life. Thus, recycling facilities need to consider alternative methods. Detection at the recycling center would be ideal because it would eliminate the need for consumers to be aware of proper disposal. However, this approach requires that the material be processed so that every piece of wood can be examined. In the case of the Oregon facility, the chipper is mobile and has a relatively short conveyor system that would make it difficult to assess every piece of wood. Even when assessment is possible, problems arise because of the difficulty in sorting individual samples. A number of approaches have been examined for detecting wood treated with waterborne preservatives which would most likely be present in a recycling stream. As mentioned earlier, metal treated wood in many locations tends to weather to a greyish colour that makes it virtually indistinguishable from weathered non-treated wood. Thus, visual detection is likely to be very inaccurate except where other factors, such as the use of dyes or incising in the western U.S. make the wood more recognizable. Nearly all of these systems are copper-based and there are several very sensitive indicators that might be useful. These indicators would have to be sprayed on all of the wood pieces in order to be used. That would require sizable quantities of indicator and some time for the reaction to become evident. This would make it difficult to apply in an industrial environment. There are similar indicators capable of detecting arsenic but these systems would suffer from the same problems. These indicators would also not be suitable for newer materials entering the waste stream, since arsenic based systems were phased out of the residential market in 2003 and will therefore

represent an ever-decreasing percentage of the treated material of potential concern.

Heavy metals can also be detected using x-ray technologies, notably x-ray fluorescent spec‐ troscopy (XRF). XRF is widely used in quality control programs for assessing the amounts of copper, zinc, arsenic and chromium in preservative treated wood. It is fairly sensitive to low levels of metal and preliminary studies indicate that the method even detected residual metals in wood through surface coatings [12, 13]; however, it does use ionizing radiation and most

those found in soils from most other locations in North America.

**4. Preventing contamination of recycled wood**

112 Recycling Materials Based on Environmentally Friendly Techniques

at the other sites.

An emerging technology for sorting treated wood is laser induced breakdown spectroscopy (LIBS), which uses a laser beam to degrade a segment of the wood surface to produce plasma. The wavelength of the emission from this plasma flash can be characterized spectroscopically to detect the presence of specific elements of interest. This system can also detect coatings, including those with lead based paints, and, if additional pulses are used, can remove the surface coating to detect a preservative underneath [12]. However, each additional laser pulse adds to the time required to assess each sample, thereby slowing production. The system is also sensitive to moisture, which requires additional laser pulses. This technology, while promising, would require additional research to more fully develop it for this application and is probably not feasible given the relatively low value of the resulting products.

While these technologies have the potential to remove treated wood from the recycling stream, they are less efficient because they operate at the end of the disposal path and must, therefore process large quantities of material that do not contain any treatment. Most of these techniques require additional employees or a substantial investment in sophisticated equipment. This renders such approaches inherently inefficient and costly. It is not clear that such approaches would be necessary in cases where the levels of treated wood present are low.

A far better approach to minimizing the presence of treated wood in the recycling stream would be prevention. It is not practical for haulers to remove treated wood during collection. Most haulers have nearly fully automated collection, making it extremely difficult and unsafe to attempt to remove specific contaminants during collection. However, it is possible to begin an education process for homeowners and contractors to make them more aware of the proper disposal of treated wood. For example, many haulers send notices to customers, either in conjunction with their monthly bills or as separate newsletters. These could provide venues for a gradual education of the customer base concerning disposal of treated wood. Publically operated haulers can use their local government newsletters for the same purpose. Most consumers are willing to take positive steps for the environment, provided they are not too onerous. Placing waste in different containers should fit within this arena. Informing custom‐ ers about the reasons for these efforts may require a bit of education about what treated wood is and why it does not belong in the recycling bin. This would need to be coupled with regular reminders and education as the customer base changes. It may also be useful to educate contractors about proper disposal of decking removed during renovations and to prepare any information in multiple languages in recognition that many employees do not speak English as their first language.

At the same time, where facilities allow customers to drop off materials, creating signage about sorting treated wood could help better inform facility users. In addition, creating a space where customers can drop off material inadvertently mixed into their waste will reduce the need to"sneak" materials. While these efforts are unlikely to eliminate treated wood from the recycling stream, they can reduce the incidence to the point where it does not pose a risk to the final product.

One longer term concern about the incidence of treated wood in the recycling stream will be the gradual introduction of non-metal based systems, particularly for above ground applica‐ tion such as decking. These so-called "organic" preservatives are just emerging in the market and require much more sophisticated instrumentation to detect in treated wood. Most cannot be detected visually or through the use of chemical indicators. In some cases, traces of metals or boron to overcome the problem of using indicators to detect these components; however, it is unclear whether these materials will remain for long periods in the treated products. On the positive side, many of these preservative systems are more rapidly degraded in soil and should not pose a risk of long term accumulation. Some of these systems can also be burned provided the proper temperatures are maintained to ensure complete thermal destruction.

#### **5. Conclusions**

Treated wood appears to be a consistent presence in the recycled wood stream. Ideally, systems would be developed to sort and exclude this material; however, the low value of the resulting wood makes it difficult to justify the costs for sophisticated instrumentation required to accurately distinguish between treated and non-treated wood. The relatively small amounts present at some facilities also make it difficult to justify major capital expenses to remove a minor contaminant. Continuing customer education appears to have the greatest potential for reducing the amounts of treated wood entering the waste stream and can be accomplished with minimal cost.

#### **Author details**

Jeffrey J. Morrell

Address all correspondence to: jeff.morrell@oregonstate.edu

Department of Wood Science & Engineering, Oregon State University, Corvallis, OR, USA

#### **References**

[1] Falk, B. 1997. Wood recycling: opportunities for the woodwaste resource. Forest Products Journal 47(6):17-22.

[2] Reinhart, D., A. Behzadan, and M.S. Toth. 2011. Construction and demolition debris recovery and recycling. Final Report 61038054, Hinkley Center for Solid and Hazard‐ ous Waste Management, Gainesville Florida. 57 p.

to"sneak" materials. While these efforts are unlikely to eliminate treated wood from the recycling stream, they can reduce the incidence to the point where it does not pose a risk to

One longer term concern about the incidence of treated wood in the recycling stream will be the gradual introduction of non-metal based systems, particularly for above ground applica‐ tion such as decking. These so-called "organic" preservatives are just emerging in the market and require much more sophisticated instrumentation to detect in treated wood. Most cannot be detected visually or through the use of chemical indicators. In some cases, traces of metals or boron to overcome the problem of using indicators to detect these components; however, it is unclear whether these materials will remain for long periods in the treated products. On the positive side, many of these preservative systems are more rapidly degraded in soil and should not pose a risk of long term accumulation. Some of these systems can also be burned provided the proper temperatures are maintained to ensure complete thermal destruction.

Treated wood appears to be a consistent presence in the recycled wood stream. Ideally, systems would be developed to sort and exclude this material; however, the low value of the resulting wood makes it difficult to justify the costs for sophisticated instrumentation required to accurately distinguish between treated and non-treated wood. The relatively small amounts present at some facilities also make it difficult to justify major capital expenses to remove a minor contaminant. Continuing customer education appears to have the greatest potential for reducing the amounts of treated wood entering the waste stream and can be accomplished

Department of Wood Science & Engineering, Oregon State University, Corvallis, OR, USA

[1] Falk, B. 1997. Wood recycling: opportunities for the woodwaste resource. Forest

the final product.

114 Recycling Materials Based on Environmentally Friendly Techniques

**5. Conclusions**

with minimal cost.

**Author details**

Jeffrey J. Morrell

**References**

Address all correspondence to: jeff.morrell@oregonstate.edu

Products Journal 47(6):17-22.


## *Edited by Dimitris S. Achilias*

Reducing the amount of solid wastes in landfills is one of the main targets in nowadays wastes treatment. To this direction, there is a great need in finding of smart recycling techniques which should, as is possible, to be environmentally friendly. The intention of this book is to present some recent methods for the recycling of several materials, including plastics and wood, as well as to show the importance of composting of polymers. It targets professionals, recycling companies, researchers, academics and graduate students in the fields of waste management and polymer recycling in addition to chemical engineering, mechanical engineering, chemistry and physics. This book comprises 5 chapters covering areas such as, recycling of polystyrene, polyesters, PC, WEEE and wood waste, together with compostable polymers and nanocomposites.

Photo by moonrise / DollarPhoto

Recycling Materials Based on Environmentally Friendly Techniques

Recycling Materials Based

on Environmentally Friendly

Techniques

*Edited by Dimitris S. Achilias*