Ethanol is a simple alcoholic compound having high octane number. It is an oxygenated fuel. Bioethanol is ethanol that is derived exclusively from plant starch or cellulose as a byproduct of fermentation. The mixing of ethanol into petroleum base automobile fuels decreases the release of green-house gas emissions. Moreover ethanol is safer than common additive MTBE. Combustion of bioethanol results in cleaner emissions. The bioethanol from cellulosic feed stock is classified as second generation biofuel. Lignocellulosic biomass composed of different carbohydrate polymers (cellulose & hemicellulose), lignin, and small fraction of extractable acid, salt, minerals etc. It is the biodegradable portion of products, wastes, organic residues from agriculture and agroindustry, forestry and wood industry. Lignocellulosic biomass has been projected to be one of the main sources of economically alternative bioethanol production. Lignocellulosics can be obtained from corn stover, sugarcane bagasse, wheat straw, rice straw, oat hull, rice hull cotton stalk, parts of Lantana camara, water hyacinth etc. Bioethanol production based on lignocellulosic biomass requires multistep complex conversion technology. Milling, pretreatment, enzymatic hydrolysis, fermentation and distillation steps are involved. Genetically engineered strains of Zymomonasmobilis, S. cerevisiae are widely used. P. stiptis and Candida shehataehaving the ability of fermenting both hexose (glucose) and pentose (xylose) sugars to ethanol. Second generation bioethanol production fulfills the delusive gap of first generation bioethanol production from non-edible renewable feed stock. Production of bioethanol from lignocellulosics still requires considerable R &D before reaching the commercial production stage.

Keywords: Ethanol; Renewable energy; Bioethanol; Lignocellulosics; Fermentation.