Xylose production and the associated integration for biocoal production

Abstract

Abstract Xylose is the second most abundantly available sugar in nature next to glucose. It is one of the hemicellulose based (C5) sugars and is often discarded during the conversion of lignocellulosic biomass to biofuels. Xylose recovery as a coproduct has a great potential to reduce the overall production cost of biofuels through increased revenue and efficient utilization of biomass. A low-energy non-conventional xylose production process from the University of Louisville (UofL) uses a boron capturing agent to esterify xylose, isolate it from aqueous hydrolyzate stream, and recover xylose as a dry product under ambient process conditions. Effective integration of this xylose production as a pre-step for processing biomass to biofuels such as biocoal has significant advantages in terms of enhanced product quality and improved economics. The xylose separation process yields modified biomass with stripped of hemicellulose and alkaline ash leading to reduced oxygen content and has higher energy density. TGA study showed that such modified biomass needs low energy input for carbonization during the torrefaction process. This modified biomass doubles up as a binder during the densification process to produce biocoal, thus significantly minimizing the cost of biocoal production. The preliminary techno-economic analysis for a biocoal plant based on wood chips indicate that xylose integration imparts greater viability of the plant even when the raw material costs are more than $40 per ton while significantly cutting down the payback time.