The Effect of Biomass Densification on Structural Sugar Release and Yield in Biofuel Feedstock and Feedstock Blends

Abstract

In this work, we examined the behavior of feedstock blends and the effect of a specific feedstock densification strategy (pelleting) on the release and yield of structural carbohydrates in a laboratory-scale dilute acid pretreatment (PT) and enzymatic hydrolysis (EH) assay. We report overall carbohydrate release and yield from the two-stage PT-EH assay for five single feedstocks (two corn stovers, miscanthus, switchgrass, and hybrid poplar) and three feedstock blends (corn stover-switchgrass, corn stover-switchgrass-miscanthus, and corn stover-switchgrass-hybrid poplar). We first examined the experimental results over time to establish the robustness of the PT-EH assay, which limits the precision of the experimental results. The use of two different control samples in the assay enabled us to identify (and correct for) a small bias in the EH portion of the combined assay for some runs. We then examined the effect of variable pretreatment reaction conditions (residence time, acid loading, and reactor temperature) on the conversion of a single feedstock (single-pass corn stover, CS-SP) in order to establish the range of pretreatment reaction conditions likely to provide optimal conversion data. Finally, we applied the assay to the 16 materials (8 feedstocks in 2 formats, loose and pelleted) over a more limited range of pretreatment experimental conditions. The four herbaceous feedstocks behaved similarly, while the hybrid poplar feedstock required higher pretreatment temperatures for optimal results. As expected, the yield data for three blended feedstocks were the average of the yield data for the individual feedstocks. The pelleting process appears to provide a slightly positive effect on overall total sugar yield.

Supply and value chain analysis of mixed biomass feedstock supply system for lignocellulosic sugar production

“…Structural composition was gathered from previous studies; and their conversion rates were obtained from NREL recent study …”

“…Biomass slurry and chemicals are conveyed through centrifugal pumps. The operating temperature and time for pretreatment reactor are set in this study at 160°C and 6 min, respectively . Table summarizes the cellulose and hemicellulose fractions of the biomass types, and their conversion yields.…”

“…A total hydrolysis time of 72 h is assumed here because most of the data used in this study are based on 72 h of enzymatic hydrolysis. The experimental data on cellulose and hemicellulose conversions during enzymatic hydrolysis were collected from a recent study conducted by NREL with single and mixed feedstocks . Table summarizes data used for baseline analysis and its extreme values.…”

“…Third, appropriate feedstock blending operations may improve biomass uniformity, which may lead to synergistic benefits through biorefinery conversion operations beyond the use of individual feedstocks . Recent experimental efforts with mixed biomass feedstocks in the forms of pellets or powders with ionic liquid, alkali, and dilute acid pretreatments reported more than 90 wt% conversion of structural carbohydrates into sugars. Fourth, mixed feedstocks could be more affordable, sustainable, and practicable irrespective of the location of biorefinery .…”

Blended Feedstocks for Thermochemical Conversion: Biomass Characterization and Bio-Oil Production From Switchgrass-Pine Residues Blends

“…Recently, several different pretreatments and bioprocesses have been applied to blended feedstocks in the scope of biochemical conversion. These comprise pretreatments such as steam, SO 2 -catalyzed steam, dilute acid, ionic liquid, and bioconversion processes including enzymatic hydrolysis, fermentation, and organosolv fractionation (Shi et al, 2013;Astner et al, 2015;Vera et al, 2015;Wolfrum et al, 2017).…”