Impact of preprocessing on bioconversion yields from densified and blended feedstocks

Two strategies being investigated to reduce the cost of feedstocks logistics and improve feedstock quality are densification and feedstock blending. Densifying biomass can reduce transportation costs while producing materials with consistent physical properties such as bulk density, particle shape, size, and distribution. Blending biomass allows access to regional feedstocks and reduces grower payment by blending high quality feedstocks with lower cost feedstocks.  Published data on the impact of these combined strategies on carbohydrate and lignin yields from blended and densified feedstocks is limited. In addition, preprocessing at the biorefinery setting employing continuous operation can include steps to reduce biomass recalcitrance and bioconversion requirements. Deacetylation and acid impregnation, employed at pilot scale, prior to dilute acid pretreatment, have been shown to increase both pretreatment and enzymatic yields in non-densified, single feedstocks. Initial results suggest that when combined with preprocessing can reduce fines, in the form of extractives, soluble protein and carbohydrates, ash content. We report on the impact of preprocessing on particle size and distribution, bioconversion yields for both carbohydrates and lignin after dilute acid pretreatment and enzymatic hydrolysis of corn stover, switchgrass and a 50:50 mixture of corn stover and switchgrass blend, in both densified and non-densified format.