Impact of moisture content on the storage performance of corn stover biomass

Variable moisture content of herbaceous crop residues at harvest impacts material stability in storage and ultimately feedstock logistics and processing economics. Despite this recognized variability, many logistics case studies rely on low moisture baled feedstock to reduce handling costs and preserve dry matter. While moisture contents above 20% risk unacceptable losses in aerobic feed and forage storage, no quantitative relationship exists between corn stover moisture content and rates or extents of degradation for biomass use. Without such a relationship the cost of wet aerobic storage, both to the producer and refinery, cannot be reliably estimated. In this work corn stover was stored using laboratory storage reactors at a range of initial moisture contents (20%, 25%, 30%, 36%, and 52%) to evaluate differences in self-heating, dry matter loss, chemical composition, and sugar yield. The results show that storage behavior is dramatically impacted by moisture content, with dry matter losses ranging from 8% to 28% across the measured moisture content range. The chemical composition of these materials differed proportionately to the extent of dry matter loss, though even the most severe cases yielded quantities of sugar comparable to fresh material when processed through dilute acid pretreatment and enzymatic hydrolysis.  The results of this work provide a defensible relationship between biomass moisture content and dry matter loss rates and extents in storage to better equip economic analyses of supply system risk to variable feedstock quality.