Tuesday, April 30, 2013: 8:25 AM
Grand Ballroom I, Ballroom Level
Mechanical densification of biomass offers significant benefits for transportation, handling, and long-term storage; however, knowledge regarding the performance of densified biomass in biochemical processes is limited. The effects of densification on biochemical conversion were explored here using two different pretreatment processes. Pelleted corn stover was generated from bales that were milled to 6.35 mm. Screening experiments using dilute acid pretreatment (0.8% H2SO4, 121 °C, 3.3% solids loading and 30 min.) and simultaneous saccharification and fermentation (SSF) were performed to evaluate pretreatment efficacy and ethanol yields achieved for pelleted and ground stover formats (6.35 mm and 2 mm grinds). Additional pretreatment experiments were conducted using a larger, high-solids reactor to evaluate the impact of densification across a wider range of pretreatment conditions. The ground and pelleted corn stover was pretreated using a Zipperclave® reactor (0.8% acid, 25% solids loading, using a range of pretreatment severities Ro from 1.5 to 3.3), coupled with enzymatic hydrolysis of the pretreated materials. Using the screening method, monomeric xylose yields were significantly higher for pellets (~60%) than for ground formats (~38%). Pellets achieved ~84% of theoretical ethanol yield (TEY); ground stover formats had similar profiles, reaching ~68% TEY by day seven. Results from the larger scale pretreatment experiments indicated similar profiles of increased xylose and glucose yields from combined pretreatment and enzymatic hydrolysis of the pelleted corn stover (79%, 80%) compared to the ground stover (65.3%, 65%). Pelleting corn stover was not detrimental to pretreatment efficacy and enhanced ethanol and sugar yields under the conditions tested.