Lignocelluloses: An Economical and Ecological Resource for Bio-Ethanol Production – A Review

Abstract

At present, the world is confronted with the twin crises of fossil fuel depletion and environmental degradation. This has made the search for alternative and renewable sources of energy inevitable. Today, examples of such efforts are seen in the production of biofuels from wastes of organic origin, often known as Lignocellulosic Biomass. Lignocellulosic wastes are generated during the industrial processing of agricultural products. These wastes are generated in large amounts throughout the year, and are the most abundant renewable resources on earth. Due to their large availability and composition rich in compounds they could be used in other processes, there is a great interest on the reuse of these wastes, both from economical and environmental viewpoints. This paper present a concise overview of lignocelluloses, their chemical composition, economical and biotechnological potentials in bio-ethanol production with special emphasis on the choice of lignocellulosic substrates, pretreatment methods and types of microorganisms that have been used for optimal, ecological and economic production of ethanol. Also reviewed are the different methods used to improve microbiological lignocellulolytic enzymatic systems including the current status of the technology for bio-conversion of lignocellulose residues by microorganisms (particularly yeasts and fungi), with focus on the most economical and eco-friendly method for ethanol production. Although the production of bioethanol offers many benefits, more research is needed in the aspects like feedstock preparation, fermentation technology modification, etc., to make bioethanol more economically viable. This paper opined that lignocellulosic waste will become the main feedstock for ethanol production in the near future. Scaling up the production of lignocellulosic ethanol, however, requires further reduction of the production cost. Conclusively, the review suggested that in order to improve the technology and reduce the production cost, two major issues have to be addressed: i) improving technologies to overcome the recalcitrance of cellulosic biomass conversion (pretreatment, hydrolysis and fermentation) and ii) sustainable production of biomass in very large amounts.