Conceptual net energy output for biofuel production from lignocellulosic biomass through biorefining

There is a lack of comprehensive information in the retrievable literature on pilot scale process and energy data using promising process technologies and commercially scalable and available capital equipment for lignocellulosic biomass biorefining. This study conducted a comprehensive review of the energy efficiency of selected sugar platform biorefinery process concepts for biofuel production from lignocelluloses. The process data from approximately a dozen studies that represent state-of-the-art in cellulosic biofuel production concepts, along with literature energy input data for agriculture operations, were analyzed to provide estimates of net energy production. It was found that proper allocation of energy input for fertilizer and pesticides to lignocellulosic biomass and major agriculture or forestry products, such as corn and lumber in corn farming and lumber plantations, respectively, were critical. The significant discrepancies in literature data suggest studies are needed to determine energy inputs for fuel in farming and farm machinery. Increasing solids loading in pretreatment to at least 25% is critical to reducing energy input in a biorefinery. Post thermo-chemical pretreatment size reduction approach should be adopted for energy efficient woody biomass processing. When appropriate pretreatment technologies are used, woody biomass can be processed as efficiently as herbaceous biomass and agricultural residues. Net energy output for cellulosic ethanol was estimated to range approximately from -500-2000 MJ/ton biomass (HHV base): indicating that the energy input/output ratio is approximately 1:1 for cellulosic ethanol. However, net energy can reach approximately 4000-7000 MJ/ton of biomass when energy from lignin is included. Published by Elsevier Ltd.