Effect of torrefaction for the pretreatment of rice straw for ethanol production

BACKGROUND Rice straw is an attractive lignocellulosic material for ethanol production, since it is one of the most abundant renewable resources. It generally has high cellulose and hemicellulose contents that can be readily hydrolysed into sugars for subsequent ethanol fermentation. The pretreatment method plays an important role in increasing the efficiency of enzymatic saccharification, thereby making the whole process economically viable. Torrefaction is an appropriate pretreatment technique for enhancing the enzymatic reaction and subsequent ethanol production. RESULTS The effects of two important parameters, i.e. residence time (20, 40 and 60min) and temperature (160, 180, 200, 220, 240 and 260 degrees C), were studied under an inert atmosphere. The highest yield of 351 +/- 5.49mgg(-1) total sugars was obtained after torrefaction treatment at 220 degrees C for 40min, representing a 60.68% increase compared with the untreated sample. Based on ethanol studies conducted on rice straw, this estimated quantity of sugars could produce 150 +/- 2.40mgg(-1) ethanol, a 50.67% increase compared with the untreated sample under anaerobic conditions. The fermentation rate was enhanced by adding 0.4mmolL(-1) benzoic acid. CONCLUSION The use of this waste material could reduce competition with food materials for ethanol production. It can be considered as an alternative sustainable waste management option. (c) 2013 Society of Chemical Industry