**4. Biochar production**

Biochar is known as "biological charcoal" which is produced from large biomass of organic materials in the presence of little or no oxygen "at relatively low temperature (<700°C)" [33]. It is the carbon-rich product obtained when biomass, such as wood, manure or leaves, is heated in a closed container with little or no available air. It is also known to be of tremendous benefits to soil microbial population, improve growth of crops and soil functions. It is very helpful in environmental protection. Biochar, when used as a soil amendment, has been reported to boost soil fertility and improve soil quality by raising soil pH, increasing water holding capacity, attracting beneficial organisms like fungi and microbes, improving cation exchange capacity (CEC) and retaining nutrients in soil [34–36]. Another major benefit associated with the use of biochar as a soil amendment is its ability to sequester carbon from the atmosphere-biosphere pool and transfer it to soil [37, 38]. It may also decrease emissions of other more potent greenhouse gases (GHG) such as N2O

**93**

*The Use of Waste Management Techniques to Enhance Household Income and Reduce Urban…*

and CH4. It may persist in soil for a long period of time because it is very resistant to

One of the challenges in characterizing biochar as a class of materials is that it is new and unique [33]. Nevertheless, the defining property is that the organic portion of biochar has a high carbon (C) content which comprises the so-called aromatic compounds characterized by rings of six C atoms linked together without oxygen

Some essential nutrients can be depleted in biochar due to the pyrolysis method used in its production. Some materials are heat labile, especially at the surface of the material, while other nutrients become concentrated in the remaining biochar. Individual elements are potentially lost to the atmosphere, fixed into unavailable forms or released as soluble oxides during pyrolysis. For wood-based biochar, carbon (C) volatizes around 100°C, N above 200°C, S above 375°C and K and P between 700 and 800°C, while volatilization of magnesium (Mg), calcium (Ca) and manganese (Mn) occurs at a temperature above 1000°C. Biochar additions to soil do provide a modest contribution of nutrients depending, in part, upon the nature of the feedstock (wood versus manure) and the temperature under which

Much of the current understanding of the properties of biochar is derived from studies centred on the phenomenon known as "Terra Preta". Terra Preta (meaning black in Portuguese) refers to the expanse of very dark, fertile soils mostly found in the Amazon Basin of Brazil. The majority of the biochar applied and incorporated within the soil in this region of the Amazon over countries underwent various changes and became microscopically unrecognizable while enriching the soil with nutrients and changing soil properties. This implies that biochar, when added to soil, undergoes changes slowly but surely over the years. Change in soil properties has been recorded in different soils to which biochar was added. Increase in cation exchange capacity and pH of soil as a result of biochar addition

Biochar can be produced from a variety of biomass materials, otherwise known

as feedstock. These include biological, decomposable materials like wood and wood-based waste materials, municipal waste, domestic wastes, agricultural/ industry wastes, etc., depending on its availability and abundance. The production of biochar from materials with high economic benefits and other competing uses will however not be sustainable. Biochar can be produced at almost any pH between 4 and 12 [32, 33] and can decrease to a pH value of 2.5 after short-term incubation of 4 months at 70°C. The pyrolysis temperature of biochar production and its pH are directly proportional. The burning and natural decomposition of biomass and particular agricultural waste adds large amounts of CO2 to the atmosphere. Biochar that is stable, fixed and recalcitrant carbon are known to be capable of storing large amount of greenhouse gases; hence, it has the potential of reducing or stalling the increase in atmospheric greenhouse gas levels. It can also be used to improve water quality, increase soil fertility and raise agricultural productivity. Biochar, like coal, can sequester carbon in the soils for hundreds to thousands of years; hence, it has the potential of helping the withdrawal of CO2 from the atmosphere while producing and consuming energy. It is estimated that the sustainable use of biochar could reduce the global net emissions of carbon dioxide (CO2), methane and nitrous oxide by up to 1.8 pg. CO2−C equivalent (CO2▬CC) per year. Biochar is a high-carbon, fine-grain residue which can be produced through modern pyrolysis processes. Pyrolysis is the direct thermal decomposition of biomass in the absence of oxygen to obtain an array of solid (biochar), liquid (bio-oil) and gas (syngas) products. The specific yield from the pyrolysis is dependent on the type of process, temperature,

feedstock and other conditions that it is subjected to.

*DOI: http://dx.doi.org/10.5772/intechopen.85580*

(O) or hydrogen (H).

the material is formed.

has been documented.

microbial decomposition and mineralization.

#### *The Use of Waste Management Techniques to Enhance Household Income and Reduce Urban… DOI: http://dx.doi.org/10.5772/intechopen.85580*

and CH4. It may persist in soil for a long period of time because it is very resistant to microbial decomposition and mineralization.

One of the challenges in characterizing biochar as a class of materials is that it is new and unique [33]. Nevertheless, the defining property is that the organic portion of biochar has a high carbon (C) content which comprises the so-called aromatic compounds characterized by rings of six C atoms linked together without oxygen (O) or hydrogen (H).

Some essential nutrients can be depleted in biochar due to the pyrolysis method used in its production. Some materials are heat labile, especially at the surface of the material, while other nutrients become concentrated in the remaining biochar. Individual elements are potentially lost to the atmosphere, fixed into unavailable forms or released as soluble oxides during pyrolysis. For wood-based biochar, carbon (C) volatizes around 100°C, N above 200°C, S above 375°C and K and P between 700 and 800°C, while volatilization of magnesium (Mg), calcium (Ca) and manganese (Mn) occurs at a temperature above 1000°C. Biochar additions to soil do provide a modest contribution of nutrients depending, in part, upon the nature of the feedstock (wood versus manure) and the temperature under which the material is formed.

Much of the current understanding of the properties of biochar is derived from studies centred on the phenomenon known as "Terra Preta". Terra Preta (meaning black in Portuguese) refers to the expanse of very dark, fertile soils mostly found in the Amazon Basin of Brazil. The majority of the biochar applied and incorporated within the soil in this region of the Amazon over countries underwent various changes and became microscopically unrecognizable while enriching the soil with nutrients and changing soil properties. This implies that biochar, when added to soil, undergoes changes slowly but surely over the years. Change in soil properties has been recorded in different soils to which biochar was added. Increase in cation exchange capacity and pH of soil as a result of biochar addition has been documented.

Biochar can be produced from a variety of biomass materials, otherwise known as feedstock. These include biological, decomposable materials like wood and wood-based waste materials, municipal waste, domestic wastes, agricultural/ industry wastes, etc., depending on its availability and abundance. The production of biochar from materials with high economic benefits and other competing uses will however not be sustainable. Biochar can be produced at almost any pH between 4 and 12 [32, 33] and can decrease to a pH value of 2.5 after short-term incubation of 4 months at 70°C. The pyrolysis temperature of biochar production and its pH are directly proportional. The burning and natural decomposition of biomass and particular agricultural waste adds large amounts of CO2 to the atmosphere. Biochar that is stable, fixed and recalcitrant carbon are known to be capable of storing large amount of greenhouse gases; hence, it has the potential of reducing or stalling the increase in atmospheric greenhouse gas levels. It can also be used to improve water quality, increase soil fertility and raise agricultural productivity. Biochar, like coal, can sequester carbon in the soils for hundreds to thousands of years; hence, it has the potential of helping the withdrawal of CO2 from the atmosphere while producing and consuming energy. It is estimated that the sustainable use of biochar could reduce the global net emissions of carbon dioxide (CO2), methane and nitrous oxide by up to 1.8 pg. CO2−C equivalent (CO2▬CC) per year. Biochar is a high-carbon, fine-grain residue which can be produced through modern pyrolysis processes. Pyrolysis is the direct thermal decomposition of biomass in the absence of oxygen to obtain an array of solid (biochar), liquid (bio-oil) and gas (syngas) products. The specific yield from the pyrolysis is dependent on the type of process, temperature, feedstock and other conditions that it is subjected to.

*Elements of Bioeconomy*

**Figure 3.**

*peels and finished compost, respectively.*

know-how. It is cheap and can be made on-site where wastes are deposited, thus reducing cost of transport. As an organic fertilizer, it has the ability to release nutrient slowly into the soil, thereby making the effect to last longer, even to the succeeding crops. It creates a good environment for soil microbes, by providing carbon compounds which serve as nutrients for soil micro-organisms and other soil habitats. Compost manure due to its composition is the storehouse of all essential macro- and micronutrients required by plants. When composts are fortified with other amendments, it can be used to control plant diseases and reduce crop losses on the field. [30]'s report indicated that this type of product significantly reduced the need for pesticide, fungicide and nematode application, which could cause environmental pollution. Matured compost should conform to at least one of the four tests outlined below: (i) The carbon to nitrogen ratio (C: N) must be less than 25:1, and seed germination using radish in the compost is at least 90% of control. (ii) The compost is cured and does not reheat to 20°C above ambient temperature. (iii) The compost is cured and there is a 60% weight reduction of organic material. (iv) The material is cured under aerobic conditions without reheating.

*Composting materials and matured compost; a, b, c and d are composting using bins, poultry manure, cassava* 

Biochar is known as "biological charcoal" which is produced from large biomass of organic materials in the presence of little or no oxygen "at relatively low temperature (<700°C)" [33]. It is the carbon-rich product obtained when biomass, such as wood, manure or leaves, is heated in a closed container with little or no available air. It is also known to be of tremendous benefits to soil microbial population, improve growth of crops and soil functions. It is very helpful in environmental protection. Biochar, when used as a soil amendment, has been reported to boost soil fertility and improve soil quality by raising soil pH, increasing water holding capacity, attracting beneficial organisms like fungi and microbes, improving cation exchange capacity (CEC) and retaining nutrients in soil [34–36]. Another major benefit associated with the use of biochar as a soil amendment is its ability to sequester carbon from the atmosphere-biosphere pool and transfer it to soil [37, 38]. It may also decrease emissions of other more potent greenhouse gases (GHG) such as N2O

**92**

**4. Biochar production**

**Figure 4.**

*Biochar made from sawdust; a and b represent milled biochar and biochar in granular form respectively.*

Biochar application to soil has the potential to positively improve the soil health and increase availability of both macro- and micronutrient elements in the soil. The application of biochar can decrease the Al saturation of acid soils which often is a major constraint for productive cropping in highly weathered soils of the humid tropics. Biomass production to obtain biofuels and biochar for carbon sequestration in the sol is a carbon-negative process, i.e. more CO2 is moved from the atmosphere than released, thus enabling long-term sequestration. A recent study indicated that appropriate combinations of these feed stalks will produce good fertilizer blends with optimum nutrient availability. For example, a feed stalk with plantain peels/wastes contains high content of potassium [39], while citrus waste-based biochar has higher N and P content. Biochar made from sawdust is presented in **Figure 4**.
