Optimizing on-farm pretreatment of perennial grasses for fuel ethanol production.
Switchgrass (Panicum virgatum L.) and reed canarygrass (Phalaris arundinacea L.) were pretreated under ambient temperature and pressure with sulfuric acid and calcium hydroxide in separate experiments. Chemical loadings from 0 to 100g (kg DM)(-1) and durations of anaerobic storage from 0 to 180days were investigated by way of a central composite design at two moisture contents (40% or 60% w.b.). Pretreated and untreated samples were fermented to ethanol by Saccharomyces cerevisiae D5A in the presence of a commercially available cellulase (Celluclast 1.5L) and beta-glucosidase (Novozyme 188). Xylose levels were also measured following fermentation because xylose is not metabolized by S. cerevisiae. After sulfuric acid pretreatment and anaerobic storage, conversion of cell wall glucose to ethanol for reed canarygrass ranged from 22% to 83% whereas switchgrass conversions ranged from 16% to 46%. Pretreatment duration had a positive effect on conversion but was mitigated with increased chemical loadings. Conversions after calcium hydroxide pretreatment and anaerobic storage ranged from 21% to 55% and 18% to 54% for reed canarygrass and switchgrass, respectively. The efficacy of lime pretreatment was found to be highly dependent on moisture content. Moreover, pretreatment duration was only found to be significant for reed canarygrass. Although significant levels of acetate and lactate were observed in the biomass after storage, S. cerevisiae was not found to be inhibited at a 10% solids loading.
Digman
Matthew F
MF
United States Department of Agriculture, Agricultural Research Service, US Dairy Forage Research Center, Madison, WI 53706, United States. digman@wisc.edu
Shinners
Kevin J
KJ
Casler
Michael D
MD
Dien
Bruce S
BS
Hatfield
Ronald D
RD
Jung
Hans-Joachim G
HJ
Muck
Richard E
RE
Weimer
Paul J
PJ
D000383:Agriculture / Q000379:methods*; D000693:Anaerobiosis; D056804:Biofuels; D001709:Biotechnology / Q000379:methods*; D002473:Cell Wall / Q000378:metabolism; D002480:Cellulase / Q000737:chemistry; D002482:Cellulose / Q000737:chemistry; D000431:Ethanol / Q000737:chemistry*; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D006109:Poaceae / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D014994:Xylose / Q000737:chemistry; D001617:beta-Glucosidase
D056804:Biofuels; D000431:Ethanol; D002482:Cellulose; D014994:Xylose; D001617:beta-Glucosidase; D002480:Cellulase; D005947:Glucose