Fuel ethanol production from sweet sorghum bagasse using microwave irradiation

Sweet sorghum is a hardy crop that can be grown on marginal land and can provide both food and energy in an integrated food and energy system. Lignocellulose rich sweet sorghum bagasse (solid left over after starch and juice extraction) can be converted to bioethanol using a variety of technologies. The largest barrier to commercial production of fuel ethanol from lignocellulosic material remains the high processing costs associated with enzymatic hydrolysis and the use of acids and bases in the pretreatment step. In this paper, sweet sorghum bagasse was pretreated and hydrolysed in a single step using microwave irradiation. A conversion efficiency of 96% (0.82 g sugar/g bagasse) was obtained in a 5wt% sulphuric acid solution under 20 minutes of 180W microwave irradiation. An ethanol conversion efficiency of 98% (0.5 g ethanol/g sugar) was obtained after 24 hours of fermentation using a mixed culture of organisms to convert both hexose and pentose sugar in the broth. These results show the potential of producing 13 000 L/ha which is high enough to make the process economically attractiv