Evaluation of energy cane and sweet sorghum as feedstocks for conversion into fuels and chemicals

Abstract

Sweet sorghum and energy cane (high fiber cane) are potential crops for conversion into fuels and chemicals due to their low agricultural input requirements, potentially high fiber content and processing similarities with established sugarcane crops. A conceptual approach to a biorefinery producing fuels and chemicals from sweet sorghum and energy cane is proposed. The front-end of the plant processes 10,000 t/d of feedstock to extract convertible sugars by milling and concentrate them into storable syrups. The latter can be processed into gasoline, jet fuel and isoprene using proprietary technologies. The fiber remaining after extraction, called bagasse, is used in the boilers of the front-end plant to provide steam and power for entire facility and to produce additional second generation sugars by pretreatment and hydrolysis in a lignocellulosic conversion plant. Material and energy balances for the front-end plant were calculated using SugarsTM software. Results show that for the selected variety of energy cane, up to 46% of bagasse is available for further lignocellulosic conversion resulting in production of additional 33.6% of sugars. In this case, however, surplus electricity production is reduced by 86%. Calculations for sweet sorghum follow the same trend. Results show that a 13% reduction in fiber content by processing sweet sorghum instead of energy cane, reduces power export by 71% and second generation sugars by 40%.