Frontiers of Engineering Reports on Leading-Edge Engineering from the 2007 Symposium (2008) / Chapter Skim
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Process Review of Lignocellulose Biochemical Conversion to Fuel Ethanol--Bruce S. Dien
Process Review of Lignocellulose Biochemical Conversion to Fuel Ethanol--Bruce S. Dien
Pages 65-74
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From page 65... ...
Increasingly worrisome headlines related to energy security and economic interests and strident warnings from climate scientists all suggest the time has come to reduce oil usage and its related CO2 emissions. Currently three routes are available to reduce imported oil and greenhouse gas emissions associated with transportation: conserve, switch to plug-in hybrids, and rely on renewable biofuels.
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From page 66... ...
These include butanol produced by acetone-butanolethanol (ABE) fermentation of biomass, synthetic gasoline gasification produced by gasifying biomass to syngas followed by Fisher-Tropsch reformation, ethanol Perennial Energy 377 Crops Agricultural 621 Resources 368 Forest Resources 0 100 200 300 400 500 600 700 Million Dry Tons per Year FIGURE 1 U.S.
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From page 67... ...
of ethanol per dry ton of biomass, with the lower range having been demonstrated and the upper limit extrapolated from current research. BIOCHEMICAL CONVERSION Many processes have been conceptualized for converting fibrous biomass to ethanol.
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From page 68... ...
To recap, following the steam explosion the solids consist largely of lignin and cellulose, and the syrup contains most of the hemicellulose carbohydrates, water extractables, a little glucose, and minor amounts of released lignin products. Following pretreatment the solids are recovered and washed, possibly using a press.
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From page 69... ...
UNIT OPERATIONS The major processing steps for converting biomass to ethanol are pretreatment, enzymatic saccharification, fermentation, and recovery. Lignocellulose contains primarily structural carbohydrates, which are highly resistant to enzymatic conversion to monosaccharides.
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From page 70... ...
. Dilute acid pretreatment converts the hemicellulose carbohydrates directly to monosaccharides and therefore only requires cellulase blends; commercial blends containing xylanase activity can in some cases improve conversion efficiency.
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From page 71... ...
The bacterium Zymomonas mobilis also selectively produces ethanol and has been offered as a substitute for S cerevisiae.
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From page 72... ...
2002. Lignocellulosic Biomass to Ethanol Process Design and Economics Utiliz ing Co-Current Dilute Acid Prehydrolysis and Enzymatic Hydrolysis for Corn Stover.
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2003. Dilute-sulfuric acid pretreatment of corn stover in pilot-scale reactor: Investigation of yields, kinetics, and enzymatic digestibilities of solids.
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From page 74... ...
1999. Lignocellulosic Biomass to Ethanol Process Design and Economics Utilizing Co-current Dilute Acid Prehydrolysis and Enzymatic Hydrolysis Current and Future Scenarios.
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