Energy, sugar dilution, and economic analysis of hot water flow-through pre-treatment for producing biofuel from sugarcane residues

Hot water flow-through (FT) pre-treatment of cellulosic biomass for biofuel production offers key performance advantages over other pre-treatment methods. The present study aims to address the energy demand, sugar dilution, and economic concerns of using FT pre-treatment for the bioconversion of sugarcane bagasse and trash to ethanol. FT pre-treatment resulted in a lower minimum ethanol selling price ($0.82/L) than dilute acid ($1.01-1.19/L), hot water ($1.13-1.27/L) and steam explosion ($0.86-1.18/L) (the range represents different studies). Sugar dilution was not a limiting factor provided that extensive heat integration was employed, as is the case in an oil refinery. The ethanol beer to distillation contained 5.0 wt% ethanol. Integrated first-generation and second-generation plants with no external fuel supplied were examined based on conversion of sucrose, bagasse, and available cane trash. A base case was defined using FT pre-treatment which routed all of the bagasse and 31.8% of the trash to ethanol production. For an alternative best parameter' case, all of the bagasse and available trash was routed to ethanol production, leaving 1.1% of the feedstock higher heating value available for electricity exports. Ethanol yields for the base case, best parameter case and steam explosion case were 59.9, 81.6, and 50.8 L/wet ton cane respectively, representing increases of 79%, 108%, and 67% compared to the first-generation plant. Our results indicate that sugar dilution and energy consumption are not barriers to practical commercial implementation of flow-through pre-treatment, and that FT pre-treatment has potential to be economically advantageous compared to hydrothermal and dilute acid pre-treatments. (c) 2014 Society of Chemical Industry and John Wiley & Sons, Ltd.