A demonstration study of ethanol production from sweet sorghum stems with advanced solid state fermentation technology

Sweet sorghum (Sorghum bicolor (L.) Moench) is a promising energy crop for biofuel production. A demonstration study on cost-effective conversion of fermentable sugars in sweet sorghum stems into ethanol with advanced solid-state fermentation technology is presented in this paper. A continuous solid-state fermenter, which is 55 m in length and 3.6 m in diameter, is successfully operated in Inner Mongolia, China in 2011. Results show that the retention time (fermentation time) of the solid substrate is less than 30 h, and the ethanol yield reaches 90.5% of the theoretical yield. A total of 16 ton of sweet sorghum stems (with 13.5% sugar content and 70% moisture) are used to produce 1 ton of ethanol (99.5%, v/v). The cost of fuel ethanol production is $615.4 per ton (49 cent/liter) on the premise that the price of the sweet sorghum stems is $30 per ton.