Enhanced biofuel processes utilizing separate lignin and carbohydrate processing of lignocellulose

Enhanced biofuel production routes utilizing separate lignin and carbohydrate processing of lignocellulose are analyzed and compared with two conventional routes; the methanol and methane production via syngas from biomass. The enhanced processes studied are: hydrocarbons production by hydrogenation of biomass based sugars by hydrogen obtained from lignin gasification, and ethanol production by biomass hydrolysis and fermentation and conversion of residual lignin into methanol via syngas. The analysis of processes was done by rigorous flowsheet modeling including power production calculations and realistic heat integration and evaluation based on energy yield, greenhouse gas (GHG) reduction and net present value (NPV). The enhanced processes via separate lignin and sugar processing can run in two modes: either being energy self-sufficient or utilizing external low temperature heat and power. The processes can operate with high efficiency as 'waste heat and power to gas and liquids' processes for producing liquid or gaseous fuels especially when excess energy is available e.g. in summer. Of all the processes studied the enhanced hydrocarbon production process integrated with external low temperature heat source gave the largest GHG reduction and highest NPV. External low temperature heat and electricity is converted into fuels in 136% higher heating value (116% lower heating value) efficiency.