3-59: Understanding the impact of corn stover compositional variability on pretreatment performance

Corn stover is a potential large-volume lignocellulosic biomass feedstock that can be converted to fuels and chemicals. While most research efforts are focused on improving conversion yields, little is known about how the large compositional variability inherent in corn stover affects conversion yields. This study focused on assessing the impact of stover compositional variability on xylose conversion yields during dilute-acid pretreatment and on the enzymatic cellulose digestibility of the resulting treated solids. We pretreated seven compositionally-diverse corn stovers obtained from various locations throughout the United States. Each corn stover lot was pretreated at three different conditions in triplicate in a pilot-scale continuous reactor. At a medium pretreatment severity, monomeric xylose yields ranged from 30% to 70% for the different stover lots, and corresponding enzymatic cellulose digestibilities ranged from 68% to 95%. Similar results were seen at the other pretreatment severities. We found that xylose yields and enzymatic digestibility decreased with increasing acid neutralization capacity or soil content of the stover. Xylose yields also increased to a lesser extent with increasing xylan content of the stover. No other significant correlations between the stover’s component concentrations and conversion yields were found. Apparently, the compounds that neutralize acid are predominately associated with external contaminants on the stover (i.e., soil). The same conversion yields could likely be obtained with different stover lots by appropriately adjusting the acid loading during pretreatment to compensate for the neutralizing effect of the external compounds.