Pretreatment methods of ligno-cellulosic biomass: A review

Present work primarily deals with the exhaustive investigations of rapid de-lignification processes from source-sorted organic fractions that are recalcitrant in nature. Organic solid wastes (OSW) belongs to the organic fraction of municipal solid wastes (MSW) and they act as enormous potential substrate for alternative source of energy in the form of bio-fuels. Nevertheless, these substrates are not easily biodegradable and the degree of biodegradability is solely dependent on the composition & characteristic of organic solid wastes in municipal solid wastes. The component responsible for recalcitrance of organic solid wastes is lignin that occurs in variable amounts in different plant residues. In order to remove the recalcitrance from organic fraction municipal solid wastes and to make it more easily degradable by microbial consortia, certain pretreatment techniques have been adopted and they are applied either individually or in combined way for enhancement of bio-methanation i.e anaerobic digestion (AD) process. The goal of pretreatment method is to make the cellulose in micro-fibrils available for hydrolysis and improve the rate of hydrolysis. This paper reviews pretreatment techniques including physical, physico-chemical, chemical, biological methods respectively. The various effects of pretreatment on organic solid wastes are discussed separately and pretreatment methods have been compared on the basis of cost, efficiency and suitability to substrate.