Monday, May 2, 2011: 3:00 PM
Willow A-B, 2nd fl (Sheraton Seattle)
Lignocellulosic conversion processes have been optimized for specific feedstocks—their nominal chemical composition and variability. Seasonal feedstock availability necessitates storage, either on-farm or at an industrial processing facility. Storage times may extend for up to one year while feedstock is subjected to biological, chemical, and physical changes that affect its composition and performance relative to conversion. Degradation that results from fungal and microbial activity contributes to dry matter losses that decrease the quantity of feedstock exiting storage, change the composition of the remaining dry matter, and thus its value to the conversion process. We evaluated the chemical composition within a single 8’ (2.4m) rectangular bale of corn stover after 10 months of storage to examine the range of feedstock composition exiting storage within a single functional storage unit. Samples were collected along 1’ (30.5cm) intervals from the end to the center of the bale and were analyzed using the NREL laboratory analytical procedures. Constituent concentrations were similar for the pre-storage and 0’-1’ samples, indicating stability through 10 months of storage. Water-extractable constituents and lignin increased, while the concentrations of hemicellulose-related constituents decreased toward the bale’s interior. Theoretical ethanol yield decreased 14% over 4’ (1.2m). Subsequent pretreatment and simultaneous saccharification and fermentation (SFF) will be used to describe the impact of compositional changes relative to ethanol production. Results indicate that compositional changes resulting from biological activity during storage impart a wide range of chemical variability, and thus feedstock value within a single functional storage unit, such as a bale.