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

Abstract

AbstractHot 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. © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd.