Biofuel from wastes an economic and environmentally feasible resource

摘要

Environmental arguments centre on the need to reduce greenhouse gas (GHG) emissions for the sake of both the global and local environments. In this respect, the replacement of fossil fuels by biofuels in the transportation sector is necessary to help the reduction of GHG. Climate change impacts have spurred researchers and industry to look at alternate clean energy options. The concentration of CO2 in the earth's atmosphere was about 280 parts per million by volume (ppm) in 1750, before the Industrial Revolution began. By 1994 it was 358 ppm and rising by about 1.5 ppm per year. If emissions continue at the 1994 rate, the concentration will be around 500 ppm, nearly double the preindustrial level, by the end of the 21st century. Carbohydrate biomass is considered as the future feedstock for bio ethanol production because of its low cost and its huge availability. The major carbohydrate materials found in great quantities to be considered, is wheat bran, sugarcane bagasse and rape straw, which can be easily converted in to ethanol by following pretreatment either by acid or enzyme, hydrolysis and distillation process under feasible conditions. The effects of different pH and temperature with enzymatic saccharification treatment on conversion of these biomasses were studied. The produced glucose was fermented to bioethanol, using Saccharomyces cerevisiae yeast in combination with pentose fermenting enzymes as Pitchia stipititis and the amount of produced bio ethanol was measured by gas chromatography. Enzyme treatment at 30°C and pH 5 is an effective treatment method for converting lignocelluloses to glucose. Up to 23.35% glucose v/v could be achieved after enzyme treatment from bagasse than others. Fermentation of treated lignocelluloses shown that glucose after 3 days fermentation the maximum bio ethanol of 19.25% (v/v) by Saccharomyces cerevisiae and 26.75% (v/v) was attained in case of sugarcane bagasse by using Pitchia stipititis in combination with S. cerevisiae. This process is expected to be useful for the bio ethanol production from wheat bran, sugarcane bagasse and rape straw as a source of carbohydrate renewable biomass from abundant agricultural by product.