Agricultural waste: A potential renewable energy source for biobutanol production

Agricultural waste is a carbon based renewable organic energy resource. Plant biomasses are rich in lignocelluloses which contain cellulose and hemicelluloses which on hydrolysis give fermentable sugars. Lignin is a complex aromatic compound that encloses cellulose and hemicelluloses thus is troublesome for hydrolysis of cellulose and needs to be broken down either by biological or chemical means. Cellulose and hemicellulose thus liberated can be hydrolyzed biologically using enzymes and physicochemically using high pressure steam or dry heat along with acids, alkali, solvents etc. to liberate reducing sugars which can be fermented to butanol by solventogenic Clostridia. Biobutanol is a green fuel that has several applications over the other available fuels such as ethanol, methanol and petrol. However biobutanol production is commercially non-viable. Several attempts were made to economize the biobutanol production to compete with synthetic butanol. This review discusses the use of different agricultural waste and the various methods of hydrolysis and pretreatment to obtain fermentable sugars for biobutanol production. The use of agricultural waste not only economizes the process but also removes the recalcitrance from the environment, thus making the process eco-friendly.