Resolving mismatches in the flexible production of ethanol and butanol from eucalyptus wood with vacuum fermentation
In flexible ethanol-butanol plants, low tolerance to butanol by solventogenic clostridia (and resulting dilute fermentation) results in considerable number of empty fermentors whenever production focuses on ethanol. This research identified scenarios in which vacuum fermentation (in-situ vacuum recovery) may be applied to solve this problem. We conducted ethanol (Saccharomyces cerevisiae) and ABE (Clostridium beijerinckii NCIMB 8052) batch vacuum fermentations of eucalyptus hydrolysates according to the distribution of sugars in a flexible plant. Based on the experiments and performance targets set for the ABE fermentation, we simulated a flexible plant that processes 1000 dry t eucalyptus/day using pretreatment and enzymatic hydrolysis steps with moderate solids loading (15% w/w). The simulation showed that the number of fermentation tanks can decrease by 62% (eliminating 10 idle tanks, 3748 m3 each) by applying vacuum recovery only to the fermentation of mixed (cellulose + hemicellulose) hydrolysates to ABE. We concluded that this configuration can result in savings of up to 2 MMUS$/year in comparison with flexible plants having only conventional batch fermentors, and additional cost savings are expected from reduced wastewater footprint.
KeywordsProcess flexibility Eucalyptus ethanol Eucalyptus butanol In-situ product recovery Productivity
This research was funded by the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) (Grant numbers 2015/07097-5 BIOEN Program and 2016/01785-0), the FAPESP-Ohio State University collaborative research program (mobility Grant number 2015/50243-2), UNICAMP (scholarship number 38615 PAPDIC-FAEPEX), the South-Central Region Sun Grant Program (from the USDA-NIFA), and the USDA National Institute of Food and Agriculture (NIFA) Hatch Project OHO01333. We thank Fibria and Francisco Maugeri Filho (FEA/UNICAMP) for generously providing eucalyptus wood chips and the yeast used in this work, respectively.
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