Perspectives of Agro-Waste Biorefineries for Sustainable Biofuels

Abstract

The agriculture plays a significant role in a nation�s economy and efforts to feed one and all of the global population. The harvesting and processing of crops generate agro-wastes. The proper management and discard of agricultural residues and agro-industrial wastes is of concern due to environmental problems like emission of greenhouse gases, air pollution and organic waste accumulation. The agro-wastes are abundant and cheap feedstocks for second generation lignocellulosic biorefinery that overcome the criticisms and short comings faced by biorefinery based on food crops. The huge prospects are present in conversion and recovery of eco-friendly products from agro-wastes by safeguarding pressure on arable land, savings on fossil fuel consumption and also leading to global food security. The biorefineries based on agro-wastes are well studied for residues like straw from rice, maize, wheat, maize cobs and agro- processing wastes such as rice husks, vegetable and fruit peels, sugarcane bagasse and oil cakes. These resources are rich in carbohydrates, proteins, lipids and other biocompounds. The carbohydrates are recovered from agro-wastes by pre-treatment methods and helps in production of the bioethanol and biobutanol by fermentation. The lipid content in agro-wastes is used for biodiesel production by transesterification. The bio-oils and syngas from the agricultural residues are produced by thermochemical treatments namely pyrolysis and gasification respectively. The biohydrogen and methane are produced from agro-wastes by anaerobic digestion are also products of biorefinery. The valorization of agro-wastes produce volatile fatty acids, citric acid, succinic acid, lactic acid, glutamic acid, acetic acid, xylitol, arabitol and furfural. The processes such as torrefaction, steam explosion and hydrothermal carbonization improves the fuel efficiency of pellets from agro-residues. The agro-waste biorefinery results in zero waste from the full utilization of crop residues or agro-industrial by products. The agro-waste based biorefineries are viable and sustainable approach for conversion to biofuels and biochemicals especially in developing countries. � 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.