Waste Biomass

Biomass is a renewable resource and refers to any material having recent biological origin, such as plant materials, agricultural crops, and even animal manure. According to National Renewable Energy Laboratory (NREL), biomass can be defined as any plant-derived organic matter. Biomass available for energy on a sustainable basis includes herbaceous and woody energy crops, agricultural food and feed crops, agricultural crop wastes and residues, wood wastes and residues, aquatic plants, and other waste materials including some municipal wastes. Biomass is a very heterogeneous and chemically complex renewable resource. Owing to its natural abundance, sustainability, and often low cost, biomass is a potential alternative to nonrenewable energy sources for production of chemicals. Biomass has a chemical composition comprised of C, H, O, and N, similar to fossil feedstocks which contain C and H. Currently, the annual worldwide production of biomass is estimated to exceed 100 trillion kilograms (Xu et al. 2008). However, presently, only 5 % of chemicals are derived from renewable resources (Lucia et al. 2006). Hence, there is an enormous potential for production of bio-based chemicals to compete with their fossil-derived counterparts.

Fig. 1.1 Different types of waste biomass

Types of Waste Biomass/Potential Waste Biomass Resources

Globally, 140 billion metric tons of biomass is generated every year from agriculture. The main sources of biomass waste are given below (Fig. 1.1).

Agricultural and agro-industrial wastes: Agricultural biomass generally comprises of leftovers after grain separation, such as residual stalks, straw, leaves, roots, husk, nut or seed shells, waste wood, and animal husbandry waste. Some common examples are coconut (fronds, husk, shell), coffee (hull, husk, ground), corn (cob, stover, stalks, leaves), cotton (stalks), nuts (hulls), peanuts (shells), rice (hull/husk, straw, stalks), sugarcane (leavings, bagasse, molasses), vegetable wastes, etc.

Animal husbandry wastes: Manure from cattle, poultry, and hogs.

Food processing wastes: Include by-products and leftovers processing, such as fruit pomace wastes (peels, seeds, and pulp) and wastewater sludge, brewery wastes (brewer's spent grain, spent hops, wastewaters, and surplus yeast), winery wastes (solid by-products include marcs, pomace, and stems and may account on average for almost 30 % (w/w) of the grapes and liquid sludge from organic wastewater treatment plants), starch industry wastes, dairy industry wastes (whey), and meat processing wastes.

Forestry residues: Wood chips, bark, sawdust, timber slash, and mill scrap.

Municipal waste: Solid household wastes, wastewater sludge, waste paper, and yard clippings.

Marine processing wastes: fish industry waste (scales, skin, visceral mass (viscera, air bladder, gonads, and other organs), head, fins, and visceral mass) and crustacean shell and shell fish waste (head and body carapace).

Biotechnological industry wastes: Waste fungal/bacterial/yeast/microalgae biomass.

Biodiesel industry wastes: Crude glycerol from biodiesel production.

This high volume of biomass can be converted to an enormous amount of energy and raw materials. Agricultural waste biomass converted to energy can substantially displace nonrenewable-based fossil fuels, reduce emissions of greenhouse gases (GHG), and provide renewable energy. Biomass is a renewable resource that has a steady and abundant supply, especially those biomass resources that are by-products of agricultural activity. With the increasing global concerns to combat climate change, countries are now looking for alternative sources of energy to minimize GHG emissions. Apart from being carbon neutral, the utilization of biomass for energy decreases reliance on the consumption of fossil fuel, hence, contributing to energy security and climate change mitigation while closing the carbon cycle loop. Currently, as the debate on food versus fuel gets intensified, the biomass can provide extra income to farmers without compromising the production of main food and even nonfood crops.

Although there is an increasing trend on the utilization of biomass for energy and other industrial products, biomass is still largely underutilized and left to rot or openly burned in the fields, especially in developing countries. Mostly, these countries do not have strong regulatory laws to control such environmentally unfriendly practices or either fail to implement them. As a common practice, the burning of agricultural residue (e.g., open field burning of rice stubble) results in air pollution which poses risk to human and ecological health. Biomass is a renewable resource that causes problems when not used. The challenge, therefore, is to convert biomass as a resource for energy and other productive uses.

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