Life cycle assessment-based process analysis for fuel-grade bioethanol production using rice straw

Abstract

Rice straw is a major biomass residue from rice cultivation, which reaches to a world average of 740 million tonnes/year generation. Open burning of rice straw in paddy fields is the common practice, which could result in an average greenhouse gas emission of 92 kg of CO2 eq/tonne of dry rice straw and other harmful airborne emissions. Existing studies indicate that bioethanol production from rice straw is more environmentally benign, compared to alternative options, such as gasification for combined heat and power generation and dimethyl-ether production. This study analyses the net energy indicators and carbon footprint of fuel-grade bioethanol production processes from rice straw comparing three dehydration techniques: 1. Extractive distillation, 2. Azeotropic distillation, and 3. Pressure swing distillation. Chemical process simulations using the Aspen Plus software were utilized to evaluate the bioethanol production process from rice straw, with a plant output capacity of 222 litres/hr of fuel-grade bioethanol (99.7 vol% ethanol). The results show that the most environmental benign dehydration technique is extractive distillation. The findings from this study can support decision making for future wasteto- biofuel plants using waste rice straw in the world.