Combined Effect of Densification and Pretreatment on Cellulosic Ethanol Production

Abstract

Biomass densification enhances material stability, improves flowability, and decreases both handling and transportation costs. The effect of densification, before or after pretreatment, was tested to determine the effect on cellulosic ethanol processing. Pelleting increased glucose yields of non-pretreated materials by 210% and pelleting followed by acidic and alkaline pretreatments had significant positive impacts on hydrolysis rates or yields. The increase in sugar yields was attributed predominantly to grinding of biomass within the pellet mill. The effects of low pressure densification following AFEX pretreatment were tested under several enzyme loadings both with and without prolonged storage. Densification had no adverse effects on ethanol yields from switchgrass or corn stover; however, prairie cordgrass yields were reduced by 16%. High enzyme loading (15 FPU/g-glucan) produced 15-20% higher ethanol yields than low enzyme loading (5 FPU/g-glucan). Biomass storage by 6-months did not have any negative effects on ethanol yields of AFEX-treated and densified biomass.