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Integrating enzyme fermentation in lignocellulosic ethanol production: life-cycle assessment and techno-economic analysis

Olofsson, Johanna LU ; Barta, Zsolt; Börjesson, Pål LU and Wallberg, Ola LU (2017) In Biotechnology for Biofuels 10.
Abstract

Background

Cellulase enzymes have been reported to contribute with a significant share of the total costs and greenhouse gas emissions of lignocellulosic ethanol production today. A potential future alternative to purchasing enzymes from an off-site manufacturer is to integrate enzyme and ethanol production, using microorganisms and part of the lignocellulosic material as feedstock for enzymes. This study modelled two such integrated process designs for ethanol from logging residues from spruce production, and compared it to an off-site case based on existing data regarding purchased enzymes. Greenhouse gas emissions and primary energy balances were studied in a life-cycle assessment, and cost performance in a techno-economic... (More)

Background

Cellulase enzymes have been reported to contribute with a significant share of the total costs and greenhouse gas emissions of lignocellulosic ethanol production today. A potential future alternative to purchasing enzymes from an off-site manufacturer is to integrate enzyme and ethanol production, using microorganisms and part of the lignocellulosic material as feedstock for enzymes. This study modelled two such integrated process designs for ethanol from logging residues from spruce production, and compared it to an off-site case based on existing data regarding purchased enzymes. Greenhouse gas emissions and primary energy balances were studied in a life-cycle assessment, and cost performance in a techno-economic analysis.
Results

The base case scenario suggests that greenhouse gas emissions per MJ of ethanol could be significantly lower in the integrated cases than in the off-site case. However, the difference between the integrated and off-site cases is reduced with alternative assumptions regarding enzyme dosage and the environmental impact of the purchased enzymes. The comparison of primary energy balances did not show any significant difference between the cases. The minimum ethanol selling price, to reach break-even costs, was from 0.568 to 0.622 EUR L−1 for the integrated cases, as compared to 0.581 EUR L−1 for the off-site case.
Conclusions

An integrated process design could reduce greenhouse gas emissions from lignocellulose-based ethanol production, and the cost of an integrated process could be comparable to purchasing enzymes produced off-site. This study focused on the environmental and economic assessment of an integrated process, and in order to strengthen the comparison to the off-site case, more detailed and updated data regarding industrial off-site enzyme production are especially important.
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biotechnology for Biofuels
volume
10
publisher
BioMed Central
external identifiers
  • scopus:85014958854
ISSN
1754-6834
DOI
10.1186/s13068-017-0733-0
language
English
LU publication?
yes
id
4678a9a3-ad8a-4fbf-8ab2-194b45bc8080
date added to LUP
2017-02-24 09:11:53
date last changed
2017-05-27 03:00:02
@article{4678a9a3-ad8a-4fbf-8ab2-194b45bc8080,
  abstract     = {<br/>Background<br/><br/>Cellulase enzymes have been reported to contribute with a significant share of the total costs and greenhouse gas emissions of lignocellulosic ethanol production today. A potential future alternative to purchasing enzymes from an off-site manufacturer is to integrate enzyme and ethanol production, using microorganisms and part of the lignocellulosic material as feedstock for enzymes. This study modelled two such integrated process designs for ethanol from logging residues from spruce production, and compared it to an off-site case based on existing data regarding purchased enzymes. Greenhouse gas emissions and primary energy balances were studied in a life-cycle assessment, and cost performance in a techno-economic analysis.<br/>Results<br/><br/>The base case scenario suggests that greenhouse gas emissions per MJ of ethanol could be significantly lower in the integrated cases than in the off-site case. However, the difference between the integrated and off-site cases is reduced with alternative assumptions regarding enzyme dosage and the environmental impact of the purchased enzymes. The comparison of primary energy balances did not show any significant difference between the cases. The minimum ethanol selling price, to reach break-even costs, was from 0.568 to 0.622 EUR L−1 for the integrated cases, as compared to 0.581 EUR L−1 for the off-site case.<br/>Conclusions<br/><br/>An integrated process design could reduce greenhouse gas emissions from lignocellulose-based ethanol production, and the cost of an integrated process could be comparable to purchasing enzymes produced off-site. This study focused on the environmental and economic assessment of an integrated process, and in order to strengthen the comparison to the off-site case, more detailed and updated data regarding industrial off-site enzyme production are especially important.<br/>},
  articleno    = {51},
  author       = {Olofsson, Johanna and Barta, Zsolt and Börjesson, Pål and Wallberg, Ola},
  issn         = {1754-6834},
  language     = {eng},
  month        = {02},
  publisher    = {BioMed Central},
  series       = {Biotechnology for Biofuels},
  title        = {Integrating enzyme fermentation in lignocellulosic ethanol production: life-cycle assessment and techno-economic analysis},
  url          = {http://dx.doi.org/10.1186/s13068-017-0733-0},
  volume       = {10},
  year         = {2017},
}