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Optimizing Ethanol and Methane Production from Steam-pretreated, Phosphoric Acid-impregnated Corn Stover

Bondesson, Pia-Maria, Dupuy, Aurélie, Galbe, Mats, Zacchi, Guido
Applied biochemistry and biotechnology 2015 v.175 no.3 pp. 1371-1388
anaerobic digestion, catalysts, corn stover, energy, energy recovery, enzymatic hydrolysis, ethanol, ethanol production, fermentation, methane, methane production, phosphoric acid, saccharification, slurries, steam, sulfuric acid, temperature
Pretreatment is of vital importance in the production of ethanol and methane from agricultural residues. In this study, the effects of steam pretreatment with phosphoric acid on enzymatic hydrolysis (EH), simultaneous saccharification and fermentation (SSF), anaerobic digestion (AD) and the total energy output at three different temperatures were investigated. The effect of separating the solids for SSF and the liquid for AD was also studied and compared with using the whole slurry first in SSF and then in AD. Furthermore, the phosphoric acid was compared to previous studies using sulphuric acid or no catalyst. Using phosphoric acid resulted in higher yields than when no catalyst was used. However, compared with sulphuric acid, an improved yield was only seen with phosphoric acid in the case of EH. The higher pretreatment temperatures (200 and 210 °C) resulted in the highest yields after EH and SSF, while the highest methane yield was obtained with the lower pretreatment temperature (190 °C). The highest yield in terms of total energy recovery (78 %) was obtained after pretreatment at 190 °C, but a pretreatment temperature of 200 °C is, however, the best alternative since fewer steps are required (whole slurry in SSF and then in AD) and high product yields were obtained (76 %).