Agricultural wastes,also known as agro-wastes,refer to the residual products discarded from various farming practices.Agro-wastes consist of multiple organic and non-biodegradable substances,and they include large quantities of crop residues such as rice straw,sugarcane bagasse,wheat shell,soybean hulls,and corn stalk.Agricultural wastes also comprise a wide range of animal residues such as livestock feces and urine,poultry litter and excreta,and carcasses (or parts) of animals,as well as,agro-industrial byproducts such as sugarcane bagasse ash (a byproduct of sugar factories),cassava bagasse,soy hulls,and sugar-beet pulp.Moreover,agricultural wastes contain nitrogen and phosphorus species released from crop fertilization,as well as,toxic elements due to the utilization of pesticides (herbicides and insecticides).Furthermore,agricultural wastes include lignocellulosic biomass such as wood and straw residues,which is considered a renewable resource for the 2nd generation of biofuels production.The fractions of cellulose,hemicellulose,and lignin vary among agricultural wastes (e.g.,corn stover,rice husk,wheat straw,and sweet sorghum stalk).Based on the nature of farming systems,agro-wastes can be collected in the forms of solid,liquid,or slurry.The annual quantity of agricultural wastes has been estimated as 998 million tonnes,in which the organic fraction can reach up to 80% of the total solid wastes.
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