**1. Introduction**

Increased environmental awareness has led researchers to find alternative solutions to replace petroleum-based materials in a sustainable manner. With an increase in world's population, one of the most concerning problems the planet is currently experiencing is the cumulative waste from various industries. The world's population produce an astounding 3.6 million tonnes of municipal solid waste each day. It is projected to rise to 6.1 million tonnes per day by the year 2025. It is adversely affecting health, contaminating our air, landscape, fresh water and ocean life. Waste valorisation is one method of managing waste in a sustainable manner and in return deriving a high-value product. The meat industry constitutes many by-products, which are under-exploited, from which a large number of valuable proteins, fats and chemicals can be derived from. Specifically related to the meat industry are tanneries and rendering plants, which process bovine and cattle hides for leather and fat production.

Hide off-cuttings, shavings and finished leather scrap are generated as waste in tanneries. These are currently disposed of in landfill sites and they have high landfilling costs per mass unit due to their low density and present low compaction ability. At best, the hide off-cuttings and shavings are converted to animal feed providing little or no economical or sustainable value, despite their content in valuable biopolymers. Bovine hides are rich in the valuable protein collagen, especially in the corium layer of the skin.

Considering the high cost of collagen and the vast number of applications and industries it can be of value, a more sustainable and a waste valorisation option would be to recover as much collagen as possible from hide off-cuttings.

Collagen is a structural protein, which provides strength, stability, and flexibility and is a major constituent of the skin tissue. Hence, bovine hides contain an abundance of collagen. The collagen molecule is a triple-helix comprised of three distinct alpha chains of repeating units of (GLY-X-Y)N amino acids, where X is often proline and Y is often hydroxyproline [1, 2].

**Figure 1** shows the stages carried out in a tannery and post tanning in order to convert hides into leather. These steps result in the release of corrosive gasses into the atmosphere and in large quantities contaminated wastewater. Though leather is used for many applications, from furniture to bags and shoes and is economical in many industries, some bovine hides such as bull-hides are often too thick to process

During the conversion of bovine hides into leather (**Figure 2**) a vast number of chemicals are released into the environment and waste products are generated at each stage. **Table 1** is showing chemicals used and wasted generated at each stage of

As bovine hides are being converted to leather, additional waste is generated during the preparation steps. Collagen-rich hide off-cuttings, trimmings and defected parts end up in landfill or at best as animal protein feed which is of low

Bovine hide off-cuttings, trimmings and potentially bull-hides that are too thick to process for leather production and calf-hides that have defects can be used for collagen extraction. Collagen is the most abundant protein found in the mammalian body, making up approximately 30% of the total body protein. This structural protein which provides strength, stability and flexibility is a major constituent of skin tissue [14] and hence bovine hides are rich in collagen, especially in the corium

Hide off-cuttings can come from various bovine sources, such as bull, cow, ox, calf and even bovine face-piece hides. Additional to bovine hide off-cuttings, bullhides that are too thick to process and require additional thinning processes can also be used for collagen extraction. This reduces extra processing costs and can directly

Bovine hide off-cuttings can be processed for collagen extraction. This collagen can be used by various industries for many applications from biodegradable films, pharmaceuticals to cosmetics. Several methods and techniques can be applied to extract collagen from bovine hide off-cuttings and the most efficient, economical and environmentally favourable methods can be worked with in order to reduce chemical and solid waste. Further, the market value of collagen is a lot more than leather, ranging from \$37 per gram to as high as \$1000 per gram for native lab-

Collagen is the most abundant structural protein found in the vertebrate body. Collagen is a rigid, inextensible, fibrous protein that is the principal component of connective tissue in animals, including tendons, cartilage, bones, teeth, skin and blood vessels. As a structural protein it is mainly used to give strength to structures in the body, however, it has different functions depending on the location of the body [17]. One-third of the total protein content in the mammalian body is collagen

The triple-helix of collagen consists of three distinct alpha chains coiled around each other and this is termed as tropocollagen. The tropocollagen units are arranged

and accounts for three-quarters of the dry weight of the skin.

and requires additional processing steps for thinning of hides.

**2.2 Use of bovine hides for collagen production**

value considering the processing costs.

leather production.

*Collagen: From Waste to Gold*

*DOI: http://dx.doi.org/10.5772/intechopen.94266*

section of the hide [15].

grade collagen [16].

**3.1 Collagen structure**

**205**

**3. Collagen**

be used for collagen extraction.

Collagen is a highly sought-after protein, finding use in regenerative medicine, in cosmetics, used as casings, in supplements, films, pharmaceuticals, as a precursor to biodegradable materials, for use in tissue engineering and more recently in 3D printing [3–8]. The demand for collagen is rising at approximately 20% annually and global collagen-based biomaterials market is predicted to reach US\$5 billion by 2025. Specifically extracting bovine collagen has many advantages over other potential sources, such as having a higher denaturation temperature in comparison to collagen from marine sources, extracting fish and porcine collagen present limitations; applications of fish collagen are limited because of its lower hydroxyproline content [9] and porcine products are prohibited by Muslim and Jewish communities [10].

This chapter aims to represent a background on waste generation in tanneries, to use the tannery waste bovine hide off-cuttings for extraction of high value collagen. Further, collagen extraction methodologies are discussed in detail and finally methods used to investigate physicochemical properties of collagen are reviewed.

#### **2. Tannery processing: waste production**

In recent years waste valorisation has attracted a significant amount of attention with the sole aim of managing waste in the most sustainable way. Waste from various industries is one of the most concerning problems the planet is currently experiencing and will increase with the increase in population and needs to be addressed. The meat industry constitutes many by-products that are underexploited, from which a large number of valuable proteins, fats and chemicals can be derived from.

Tanneries and rendering plants process bovine and cattle hide for leather and fat production. Casualty and cattle used for meat consumption result in a large quantity of waste and one of the most valuable by-products is the bovine and cattle skins or hides.

Industrial rendering separates animal by-products into value-added products such as animal protein meal and rendered animal fat and tanneries aim to process hides into leather, however, a substantial amount of waste is still produced from these processes that can be used to derive high-value products. Collagen is such a product that can be extracted from hide off-cuttings that is additional waste generated during leather preparation steps. Considering the high cost of collagen and its vast number of applications, extraction of such high-value product from bovine hide off-cutting is both sustainable and economical.

#### **2.1 Impact of tannery waste on the environment**

As much as this sector is considered to play a vital role because it recycles and reuses the by-products of the meat industry, the processes carried out in the different stages have a serious environmental impact. Environmental concerns that result from tanneries are due to resource consumption such as water, chemicals, energy and the generation of emissions such as volatile organic compounds, wastewater and solid waste. Moreover, hide off-cuttings, trimmings, hair and fleshings are removed from the hides during the tanning process. Only about 25% by weight of raw salted hides results in the finished leather [11]. Furthermore, other solid wastes are also produced from wastewater and sludge treatment.

#### *Collagen: From Waste to Gold DOI: http://dx.doi.org/10.5772/intechopen.94266*

Collagen is a structural protein, which provides strength, stability, and flexibility and is a major constituent of the skin tissue. Hence, bovine hides contain an abundance of collagen. The collagen molecule is a triple-helix comprised of three distinct alpha chains of repeating units of (GLY-X-Y)N amino acids, where X is often

Collagen is a highly sought-after protein, finding use in regenerative medicine, in cosmetics, used as casings, in supplements, films, pharmaceuticals, as a precursor to biodegradable materials, for use in tissue engineering and more recently in 3D printing [3–8]. The demand for collagen is rising at approximately 20% annually and global collagen-based biomaterials market is predicted to reach US\$5 billion by 2025. Specifically extracting bovine collagen has many advantages over other potential sources, such as having a higher denaturation temperature in comparison to collagen from marine sources, extracting fish and porcine collagen present limitations; applications of fish collagen are limited because of its lower hydroxyproline content [9] and porcine products are prohibited by Muslim and Jewish communities [10].

This chapter aims to represent a background on waste generation in tanneries, to use the tannery waste bovine hide off-cuttings for extraction of high value collagen. Further, collagen extraction methodologies are discussed in detail and finally methods used to investigate physicochemical properties of collagen are reviewed.

In recent years waste valorisation has attracted a significant amount of attention

Tanneries and rendering plants process bovine and cattle hide for leather and fat production. Casualty and cattle used for meat consumption result in a large quantity of waste and one of the most valuable by-products is the bovine and cattle skins or hides. Industrial rendering separates animal by-products into value-added products such as animal protein meal and rendered animal fat and tanneries aim to process hides into leather, however, a substantial amount of waste is still produced from these processes that can be used to derive high-value products. Collagen is such a product that can be extracted from hide off-cuttings that is additional waste generated during leather preparation steps. Considering the high cost of collagen and its vast number of applications, extraction of such high-value product from bovine

As much as this sector is considered to play a vital role because it recycles and reuses the by-products of the meat industry, the processes carried out in the different stages have a serious environmental impact. Environmental concerns that result from tanneries are due to resource consumption such as water, chemicals, energy and the generation of emissions such as volatile organic compounds, wastewater and solid waste. Moreover, hide off-cuttings, trimmings, hair and fleshings are removed from the hides during the tanning process. Only about 25% by weight of raw salted hides results in the finished leather [11]. Furthermore, other solid wastes

with the sole aim of managing waste in the most sustainable way. Waste from various industries is one of the most concerning problems the planet is currently experiencing and will increase with the increase in population and needs to be addressed. The meat industry constitutes many by-products that are underexploited, from which a large number of valuable proteins, fats and chemicals can

proline and Y is often hydroxyproline [1, 2].

*Biotechnological Applications of Biomass*

**2. Tannery processing: waste production**

hide off-cutting is both sustainable and economical.

**2.1 Impact of tannery waste on the environment**

are also produced from wastewater and sludge treatment.

be derived from.

**204**

**Figure 1** shows the stages carried out in a tannery and post tanning in order to convert hides into leather. These steps result in the release of corrosive gasses into the atmosphere and in large quantities contaminated wastewater. Though leather is used for many applications, from furniture to bags and shoes and is economical in many industries, some bovine hides such as bull-hides are often too thick to process and requires additional processing steps for thinning of hides.

During the conversion of bovine hides into leather (**Figure 2**) a vast number of chemicals are released into the environment and waste products are generated at each stage. **Table 1** is showing chemicals used and wasted generated at each stage of leather production.

### **2.2 Use of bovine hides for collagen production**

As bovine hides are being converted to leather, additional waste is generated during the preparation steps. Collagen-rich hide off-cuttings, trimmings and defected parts end up in landfill or at best as animal protein feed which is of low value considering the processing costs.

Bovine hide off-cuttings, trimmings and potentially bull-hides that are too thick to process for leather production and calf-hides that have defects can be used for collagen extraction. Collagen is the most abundant protein found in the mammalian body, making up approximately 30% of the total body protein. This structural protein which provides strength, stability and flexibility is a major constituent of skin tissue [14] and hence bovine hides are rich in collagen, especially in the corium section of the hide [15].

Hide off-cuttings can come from various bovine sources, such as bull, cow, ox, calf and even bovine face-piece hides. Additional to bovine hide off-cuttings, bullhides that are too thick to process and require additional thinning processes can also be used for collagen extraction. This reduces extra processing costs and can directly be used for collagen extraction.

Bovine hide off-cuttings can be processed for collagen extraction. This collagen can be used by various industries for many applications from biodegradable films, pharmaceuticals to cosmetics. Several methods and techniques can be applied to extract collagen from bovine hide off-cuttings and the most efficient, economical and environmentally favourable methods can be worked with in order to reduce chemical and solid waste. Further, the market value of collagen is a lot more than leather, ranging from \$37 per gram to as high as \$1000 per gram for native labgrade collagen [16].
