Biphasic acid treatment of debarked cotton stalk: one novel approach towards bioethanol production

Lignocellulosic biomass includes wheat straw, corn stover, rice straw, cotton stalk etc. which are renewable resources of energy. These agricultural lignocellulosic wastes are attractive substrate for production of bioethanol. The main challenge for producing ethanol from lignocellulosic wastes is the conversion of lignin containing polymer in to delignified monomer. Acid hydrolysis is conventional process for this conversion. To avoid undesirable side reaction and minimize the environmental issues, the acid hydrolysis has divided in to two steps involving the treatment with concentrated acid in first step for decrystallization followed by dilute acid hydrolysis. In the present work effectiveness of different concentration of sulphuric acid on cotton stalk has been studied and solubilisation of fermentable sugar and specifically dextrose were checked at regular interval of time. The result of this study show that 75% H2SO4 at fixed sample-acid ratio of 1:2 (by weight) followed by dilution up to 1N, steam treatment at 121oC for 30 min. and heating up to four hour at 90oC gives maximum yield of glucose (0.24 g/g of biomass) and fermentable sugar (0.45 g/g of biomass).