It is generally recognized in the international community that biofuels are the alternative to replace the fossil fuel in large scale in the areas of transportation. Currently, sweet sorghum has attracted great attention as the first choice of non-food energy plant since it can grow under different geographic conditions, such as arid whether, on alkaline soil. Therefore sweet sorghum has the advantages of corn, sugar cane and switchgrass as a biofuel feedstock. Traditionally, the production of ethanol through sugar feedstocks, such as sweet sorghum stalks, sugar cane, or sugar beet, is done in a liquid fermentation from the biochemical conversion route. These processes require a great deal of energy to press the cane to obtain the juice, and to boil off of the water in the juice so that juice can be concentrated for storage. The liquid fermentation method may not make full use of sugar which remained in bagasse, as well as may cause serious waste water treatment issues. The proprietary advanced solid state fermentation (ASSF) process developed by Tsinghua University eliminates the need to press the cane, thereby saving a large portion of the energy and increasing sugar utilization that has the potential to make the production of ethanol more cost-effective. The fermentation time is less than 36 hours, and the fuel ethanol yield can reach to 92% of ethanol theorectical yield. While comparing to corn ethanol, the fermentation time and ethanol yield are 50 hours and 91.5%.
A demonstration plant of sweet sorghum fuel ethanol plant with the fermentor of 127m3 using ASSF technology was successfully operated in Inner Mongolia in 2009. The demon results consistent with banch scale fermentor, and match with the mathematical model that we developed. The process conditions include relatively short fermentation time less than 36 hours, and resulting with ethanol yield over 90% of theoreticl yield, with low waste water generaton and high overall energy efficiency. 15-16 tons of sweet sorghum stalks (sugar content is 14.5%) can be used to produce 1t ethanol, and feed 1 cattle. A techno-economic analysis (TEA) was also conducted for this work.
See more of this Group/Topical: Topical G: Innovations of Green Process Engineering for Sustainable Energy and Environment