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Impact of cellulase production on environmental and financial metrics for lignocellulosic ethanol
Author(s) -
Hong Yan,
Nizami AbdulSattar,
Pour Bafrani Mohammad,
Saville Bradley A,
MacLean Heather L
Publication year - 2013
Publication title -
biofuels, bioproducts and biorefining
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.931
H-Index - 83
eISSN - 1932-1031
pISSN - 1932-104X
DOI - 10.1002/bbb.1393
Subject(s) - cellulosic ethanol , cellulase , ethanol fuel , biofuel , greenhouse gas , production (economics) , yield (engineering) , environmental science , pulp and paper industry , chemistry , fermentation , cellulose , waste management , food science , economics , engineering , biochemistry , ecology , biology , microeconomics , materials science , metallurgy
The cost of cellulases remains a key issue in the production of cellulosic ethanol, and the impact of enzymes on greenhouse gas ( GHG ) emissions of cellulosic ethanol has received little attention. This study evaluates life cycle emissions and cellulase production costs for bioethanol production, considering on‐site and off‐site production options. A complete enzyme production process was simulated using AspenPlus , generating mass and energy balance information required to calculate GHG emissions and financial metrics. GHG emissions for cellulase production range from 10.2 to 16.0 g CO 2 eq g –1 enzyme protein, depending on on‐site or off‐site production and the method of transportation. Enzyme GHG emissions are predicted to be 258 g CO 2 eq. L –1 of ethanol for on‐site production, versus 403 g CO 2 eq. L –1 for off‐site production, based on a 150 MMLY ethanol plant using 11.5 mg enzyme g –1 substrate and a cellulase fermentation yield of 90%. Cellulase production costs were estimated for a range of conditions, including ethanol plant size, enzyme dose and protein yield for on‐site production, and enzyme plant size, protein yield and return on investment for off‐site production. On‐site production costs range between $3.80 and $6.75 kg –1 protein, versus $4.00 to $8.80 kg –1 for off‐site production. In both scenarios, the lowest cost corresponds to a 90% protein yield, and a high enzyme demand and production capacity. An enzyme production cost of $4.70 USD kg –1 corresponds to an enzyme cost of 0.46 USD gal –1 ($0.12 L –1 ) of ethanol in a 150 MMLY plant using 11.5 mg enzyme g –1 substrate. © 2013 Society of Chemical Industry and John Wiley & Sons, Ltd