eChapters

Vermicomposting is the rapid aerobic non-thermophilic composting technique for decomposition of various biodegradable wastes using epigeic earthworms in comparison to other conventional pit or heap composting techniques. Earthworms fragment the half decomposed organic material, mix and promote microbial activity. Worm utilizes 5-10% of food for its body growth and excretes remaining portion as vermicompost. The action of earthworm is both mechanical and biochemical. Mechanical fragmentation of the half decomposed organic material to finer particles by earthworm in its gizzard helps to increase surface area of action by microbes and aeration inside bed. Biochemical action improves the enzymatic digestion, nutrient enrichment and change in organic and inorganic contents.

Composting means decomposing organic wastes. It is a safe, non-polluting and microbiological method for disposal and recycle of organic wastes by converting those to balanced plant food materials, commonly known as compost, the organic fertilizer. In other words, the mineralization and partial humifi cation of organic materials by the action of microorganisms under suitable condition is called composting (Figure 6.1). The organic wastes undergo different physical and chemical changes with the help of microbes like bacteria, fungi, actinomycetes, etc. During composting the population of pathogenic microorganism reduces while that of benefi cial microorganism increases.

Production of any selected species of earthworm in a particular place adopting semi-natural condition is called vermiculturing. As discussed earlier in chapter 2 and 4, commercial production of certain earthworm species is essential to meet up the huge demand of earthworms for vermicomposting of organic wastes, for production of earthworm meal for pet animals, poultry and fish farming, for preparation of medicine and for their use in reducing toxic chemicals from soil and water, etc. Since during vermicomposting, earthworm multiplies in vermicompost beds, many people confuse between this two terms – vermiculturing and vermicomposing.

Solid wastes, the unavoidable consequences of civilization, are the useless and unwanted heterogeneous solid materials discarded by human being. Human greed is the major factor in creation of unwanted solid wastes. With increase in human population and its demands, there is an increase in production of various types of wastes. When human being did not come to the earth there was very little wastes like tree leaves, animal excreta or dead parts which nature used to digest and produces something beautiful every time. Still there are certain remote areas free from wastes where human being could not reach due to inaccessible condition of terrain, forests and islands. Now–a-days wastes are found even in the top of Mt. Everest or in the interior of Antarctica.

The importance of earthworms in agriculture and human health has been realized since prehistoric times. The famous Greek philosopher, Aristotle (384-322 B.C.) first described the importance of earthworm by calling them as “The intestines of the Earth”. The question, ‘How lime and charcoal from soil surface gets into lower layers?’ in the mind of Sir Charles Darwin (1809-1882 A.D.) ended up with the findings in 1837 that earthworms took those materials to lower layers and it played a significant role in formation of humified soil layer. He wrote in his book, “The formation of vegetable mould through the actions of worms” in 1881 that ‘The plough is one of the most ancient and most valuable of man’s inventions; but long before he existed the land was in fact regularly ploughed, and still continues to be thus ploughed by earthworms.

India, the second most populous country in the world after China, is trying hard to provide basic needs like food, shelter, clothes, electricity and education facility to its 1,316 million people and to upgrade itself from the stage of ‘Developing economy’ to ‘Developed economy’. Table 1.1 depicts the trend of population increase from 1154 million to 1316 million during 2009 to 2018 with diminishing growth rate from 1.42% to 1.12%. Growing demand of ever increasing population has been met so far by over exploiting natural resources like land, water, fossil fuels, forests and mineral resources which resulted rapid unplanned urbanization, quick depletion of fossil fuels, more and more waste generation, alarming increase in environmental pollution, deforestation with loss of plant and animal species, desertification of cultivable land due to soil erosion, soil contamination & soil salinity and increase in health diseases due to malnutrition, starvation and environmental pollution.

9.1 General

This chapter provides a comprehensive overview of the Life Cycle Assessment (LCA) of biochar production, focusing on the environmental impacts of its production and utilization. LCA is a systematic approach used to evaluate the environmental burdens and benefits of a product or process throughout its entire life cycle. Biochar, a carbon-rich material derived from the pyrolysis or gasification of biomass such as agricultural crop residue, forest waste, unusual wood waste, etc., has gained significant attention as a potential sustainable solid waste management, carbon sequestration, greenhouse gas mitigation, and soil amendment solution. However, understanding the environmental implications of biochar production is crucial for its sustainable implementation. The LCA approach is employed to evaluate biochar production’s different system boundaries and environmental performance, encompassing various stages such as biomass feedstock cultivation, the biochar production process, transportation, application, and end-of-life scenarios. This chapter explores the key elements of LCA, examines the methodologies employed in biochar LCA studies, and critically analyzes the environmental impacts associated with different biochar production pathways.

In order to assess the economic value of biochar, various factors need to be taken into account, including production expenses, market demand, potential income sources, and cost reductions. The economic worth of biochar can be determined by considering these factors.

8.1 Production costs

The cost of producing biochar can differ based on various factors such as the type of material used, the scale of production, the method of pyrolysis used, and the particular operational conditions.

i. Feedstock costs

• The cost of acquiring or producing biomass feedstock includes purchasing agricultural residues, forestry waste, or other biomass sources. Additional costs such as land, seeds, fertilizers, and harvesting should be considered using dedicated energy crops.

7.1 General

Science and technology have been advancing rapidly, but unfortunately, their impact has been largely negative. Pollution is not the only issue we face today, but also the depletion of fossil fuels, climate change, and excessive land degradation. The persistent presence of heavy metals in soil poses a significant threat to our planet. Many efforts have been made to remediate soils contaminated with toxic chemicals.

There are several issues that need urgent attention at the moment, and a solution is necessary to tackle them all at once. Biochar is a great option because of its numerous benefits, such as a large surface area, high porosity, high carbon sequestration rate, excess nutrients, and potential to produce syngas and bio oil. By using biochar, we can reduce the bioavailability of pollutants in soil, combat climate change by sequestering carbon, and reduce the use of fossil fuels by producing syngas and bio-oil. Additionally, biochar improves soil health, which can contribute to food security.

6.1 Characterization of solid pyrolysis products

 Biochar can be characterized for its utility as well as its energy usage. Thevarious characteristics of biochar can be categorized as follows:

i. Proximate analysis

 •            Raw moisture

 •            Hygroscopic moisture

 •            Volatile matter

 •            Ash content

 •            Fixed carbon content

 ii. Ultimate analysis

 •            Elemental compositions (C, H, N, O, S)

 iii. Physical properties

 •            True density

 •            Bulk density

 •            Porosity

 •            Dry matter

 •            Particle size

 •            Pore size

 •            Pore volume

 iv. Chemical properties

 •            pH-value

 •            Electrical conductivity

 •            Carbonate content

The classification of pyrolysis processes plays a crucial role in understanding and categorizing the various methods used for thermal decomposition of biomass, waste materials, and carbonaceous feedstocks. This chapter provides an in-depth overview of the classification schemes employed in the field of pyrolysis. It discusses the different factors considered for classification, including temperature, heating rate, feedstock, reactor configuration, and operating conditions. Understanding these classifications is essential for selecting the appropriate pyrolysis process based on specific objectives, feedstock availability, and desired product yields.

This chapter focuses on the design and performance evaluation of pyrolyzers, which are key components in producing biochar, biofuels, and other valuable products through the pyrolysis process. Pyrolyzer play a crucial role in converting biomass feedstock into desired end products, and their design greatly influences process efficiency and product quality. The chapter discusses various aspects of pyrolyzer design, including reactor types, operating conditions, heating methods, feedstock characteristics, and process optimization. It also explores performance evaluation methods to assess pyrolyzer efficiency, product yield, biochar quality, and energy consumption. The information presented in this chapter aims to provide researchers, engineers, and practitioners with valuable insights into pyrolyzer design and performance evaluation for efficient and sustainable biomass conversion.

3.1 Overview of pyrolysis technology

Pyrolysis is a process derived from the Ancient Greek words “pyro” meaning f ire and “lysis” meaning separation, which means separating by using heat or fire. This is a thermochemical conversion process that converts biomass into a useful intermediate liquid product, which can be further transformed into a hydrocarbon biofuel, oxygenated fuel additive, or substitute for petrochemicals. Pyrolysis is similar or overlapping with other thermochemical processes such as cracking, carbonization, torrefaction, destructive distillation, dry distillation, and thermolysis. It is not related to gasification, which involves chemical reactions with a gasification medium.

Biomass is a renewable and valuable resource that has many uses, including energy production, biofuels, and bioproducts. It’s made up of a complex mixture of organic compounds like cellulose, hemicellulose, lignin, proteins, fats, and minerals, which can vary depending on the source and type of biomass. Understanding the composition and properties of biomass is essential for efficient use. In this chapter, we’ll provide an overview of how to analyze and evaluate biomass as a renewable energy source. We’ll cover various techniques and methodologies for analyzing biomass, including physical, chemical, and thermal properties. We’ll discuss the importance of biomass composition, moisture content, ash content, elemental analysis, calorific value, and other relevant parameters when assessing its suitability for energy conversion. Additionally, we’ll highlight the significance of biomass characterization in understanding biomass feedstock variability and its impact on energy production efficiency, environmental performance, and sustainability.

1.1 General

Biomass is a renewable and plentiful energy source with enormous potential to meet the rising demand for clean and sustainable energy solutions. This chapter offers an overview of biomass and its conversion technology, which includes various techniques to transform biomass into useful forms of energy like heat, electricity, and biofuels.

Biomass is an organic substance obtained from plants, animals, and microorganisms. It can be utilized as a source of energy or as a basic material in various applications. The energy in biomass is derived from photosynthesis, during which plants convert sunlight, carbon dioxide, and water into organic matter. Since it comes from living or recently deceased organisms, it is a sustainable and renewable resource. In terms of carbon dioxide emissions, biomass is considered a carbon-neutral energy source because the carbon dioxide produced during combustion is offset by the carbon dioxide absorbed by plants during their growth.

The capacity of soil to function as a vital living system, within ecosystem and land use boundaries, to sustain plant and animal production, maintain or 

enhance water and air quality, and promote plant and animal health (Doran and

Zeiss, 2000). A healthy soil may function is as follows:

• Sustain biological activity, diversity, and productivity

• Regulate, store of nutrients and cycle water and, decompose organic

matter

• Filtering and buffering, degrading, mineralizing, immobilizing, and

detoxifying organic and inorganic materials

• Inactivate toxic compounds, suppress pathogens, protect water quality,

and enhance catchment soil health.

Introduction

Climate change is threatening food security globally. Countries like India are more vulnerable in view of the tropical monsoon climate and poor coping capacity of the small and marginal farmers. Several agricultural practices like indiscriminate use of agro-chemicals and crop residue burning contribute to emission of greenhouse gasses leading to warming of the atmosphere. Sequestration of carbon both in the vegetation and soil is the most effective means of mitigating GHG emissions. There are several strategies of soil carbon sequestration which can be adopted at farm level. These include: conservation agriculture, biomass recycling, crop rotations and use of organic amendments. One of the recent developments is the conversion of crop residue biomass into biochar and using the char as a soil amendment rather than directly using the crop residues. Several studies show that biochar has a long life in soil and is more effective in sequestering carbon besides improving other soil properties like water holding capacity and nutrient availability. In Indian conditions, there is an immense scope for converting millions of tonnes of crop residues which are not used as fodder into biochar and use the same for enriching soil carbon.

Introduction

Productivity has increased as a result of the significant industrialization that has occurred in India during the past 40 years. However, it has also had detrimental effects on the ecology, particularly in India where soil contamination is progressively becoming more severe. In addition to the effects of man and land use, soil is constantly adapting changes in environmental conditions. A characteristic of soil pollution is the decrease in soil productivity brought on by the presence of soil pollutants. Some changes in the soil will be temporary and reversible, while others will be permanent. Pollutants in the soil have a negative impact on the physical, chemical, and biological characteristics of the soil and decrease its production. Soil pollution is a result of a variety of factors, including pesticides, fertilizers, organic manure, chemicals, radioactive waste, abandoned food, clothing, leather goods, plastics, paper, bottles, tins, and corpses. Industrial waste contains chemicals including iron, lead, mercury, copper, zinc, cadmium, aluminum, cyanides, acids, and alkalis, among others, which either directly or indirectly enter the soil.

Introduction

Soil organic matter is an indispensible component of soil health management. It plays an important role in improving soil physical, chemical and biological environment. Soil health refers to the capacity of the soil in terms of physical, chemical and biological properties for maintaining ecosystem services. With respect to agricultural lands, soil health implies the capability of the soil towards improving crop growth and yield, while also supporting environmental sustainability. Some important determining properties of soil health maintenance are soil reaction, salinity or alkalinity, soil organic matter, soil texture, soil structure/aggregation, water holding capacity, porosity, internal drainage, and nutrient retention capacity. Simultaneously, the key properties maneuvering soil health are soil aeration, internal drainage, nutrient cycling, susceptibility to erosion etc. Except some of the basic properties (soil texture) and processes (soil erosion), most of the determinant properties and processes are maneuvered by the presence of soil organic matter. A healthy soil must have strong resistance to degradation processes and able to recover following a perturbation because of inherent resilience (Magdoff 2001).

Introduction

Rice straw is produced as a by-product of rice production at harvest. Agricultural Waste Burning (AWB) is a major contributor of air pollution in many countries, particularly in South Asia. Exposure to fine particulate matter less than 2.5 μm (micrometer), also known as PM 2.5, released by AWB can cause premature mortality due to respiratory and cardiovascular diseases (Brauer et al.,2012). Combine Harvesters used on the spring rice crop leave behind stubble and straw on the field (Sidhu et al., 2007). Farmers burn the rice residue while preparing the field for wheat sowing season that follows. Further, migrant labour from neighbouring states of Bihar and Uttar Pradesh has decreased (Sirhindi, 2019), and resulted in an increase in the cost of agricultural labour during the rice harvest season (Sharma,2018). Farmers find it both convenient and economical to burn residue to clear and prepare their fields for the next crop. In 2018, over 20 million metric tons of rice residue was generated in Punjab, of which almost 10 million metric tons was subject to open-air burning (MoA, 2019). The time window between rice harvesting and wheat sowing is just 20 to 30 days towards the conclusion of the Kharif season, which is one of the primary reasons of crop waste burning (Balwinder et al., 2016).