ABSTRACT
This chapter describes the consideration and application of chemical preprocessing to improve overall feedstock quality and handling for conversion applications. Biofuel feedstocks are not typically densified prior to delivery of the biorefinery. Dilute aqueous ammonia-based processes are effective for improving the enzyme digestibility of low-lignin feedstocks, such as corn stover, switchgrass, and miscanthus. Feedstock preprocessing sites that are not coupled with biorefineries or conversion facilities can serve as preprocessing depots that receive a broad range of feedstocks, including both high- and low-quality. Chemical preprocessing technologies to remove ash from biomass feedstocks including alkaline preprocessing, ammonia preprocessing, solvent preprocessing, acidic preprocessing, Sulfite pretreatment to overcome recalcitrance of lignocellulose pretreatments, ionic liquid pretreatments, and supercritical CO2 pretreatments. These chemical preprocessing applications vary significantly in efficacy and cost. The feedstock conversion specifications and any potential to combine with other mitigation strategies, including mechanical preprocessing and blending, are important considerations for designing an overall ash mitigation strategy.
