Fuel ethanol production from sweet sorghum bagasse using microwave irradiation

Abstract

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 attractive.

Pretreatment methods of lignocellulosic biomass for anaerobic digestion

“…Microwave heating also accelerates cellulose dissolution in ionic liquids (Zhu et al 2006a). The hydrolysis and MWR pretreatment of grass-type biomass into sugars was accomplished in one step by eliminating the hydrolysis step, making the process economically attractive (Marx et al 2014). Currently, MWR is carried out on the lab scale, as the equipment is very small, and it is still difficult to apply in potential industrial projects; thus, it is not one of the most promising pretreatment methods.…”

Sorghum: A Multipurpose Bioenergy Crop

“…This shows the potential for producing as much as 0.252 m 3 t −1 or 33 m 3 ha −1 ethanol using only the lignocellulose part of the sweet sorghum stalks. This yield is high enough to make the process economically attractive (Marx et al, 2014). The average ethanol productivity was ~220 g ethanol kg −1 of original dry stem of sweet sorghum, equivalent to 2465 L ethanol ha −1 (Cifuentes et al, 2014).…”

Influence of Sowing Times, Densities, and Soils to Biomass and Ethanol Yield of Sweet Sorghum

“…The US, Brazil, Germany, India, and China have already produced ethanol from sweet sorghum, although the production is limited as compared to cassava, maize, and sugarcane [12,13]. It is well adapted to various types of soils and provides high production biomass production [14]. The stalks of sweet sorghum may obtain 8%-23% sugar content, depending on varieties and cropping seasons, and yield >100 tons ha −1 with high lignocellulose [15,16].…”

“…Therefore, cassava waste has not been used in ethanol production in Vietnam [18]. Despite rice straw is a potential source for ethanol production, the lack of required technologies to produce high quanties of ethanol and difficulties in collecting rice straw in rural areas of Vietnam causes high prices [14]. In addition, production of ethanol from seaweed is also under research, due to Vietnam having an extensive freshwater network and a coastline of 3200 km and 639 seaweed species: of these belong 269 to Rhodophyta, 143 to Phaeophyta, 151 to Chlorophyta, and 76 to Cyanophyta [22].…”