Comparative life cycle assessment of lignocellulosic ethanol production: Biochemical versus thermochemical conversion

Dongyan Mu, Thomas Seager, P. Suresh Rao, Fu Zhao

Research output: Contribution to journalArticlepeer-review

95 Scopus citations

Abstract

Lignocellulosic biomass can be converted into ethanol through either biochemical or thermochemical conversion processes. Biochemical conversion involves hydrolysis and fermentation while thermochemical conversion involves gasification and catalytic synthesis. Even though these routes produce comparable amounts of ethanol and have similar energy efficiency at the plant level, little is known about their relative environmental performance from a life cycle perspective. Especially, the indirect impacts, i.e. emissions and resource consumption associated with the production of various process inputs, are largely neglected in previous studies. This article compiles material and energy flow data from process simulation models to develop life cycle inventory and compares the fossil fuel consumption, greenhouse gas emissions, and water consumption of both biomass-to-ethanol production processes. The results are presented in terms of contributions from feedstock, direct, indirect, and co-product credits for four representative biomass feedstocks i.e., wood chips, corn stover, waste paper, and wheat straw. To explore the potentials of the two conversion pathways, different technological scenarios are modeled, including current, 2012 and 2020 technology targets, as well as different production/co-production configurations. The modeling results suggest that biochemical conversion has slightly better performance on greenhouse gas emission and fossil fuel consumption, but that thermochemical conversion has significantly less direct, indirect, and life cycle water consumption. Also, if the thermochemical plant operates as a biorefinery with mixed alcohol co-products separated for chemicals, it has the potential to achieve better performance than biochemical pathway across all environmental impact categories considered due to higher co-product credits associated with chemicals being displaced. The results from this work serve as a starting point for developing full life cycle assessment model that facilitates effective decision-making regarding lignocellulosic ethanol production.

Original languageEnglish (US)
Pages (from-to)565-578
Number of pages14
JournalEnvironmental Management
Volume46
Issue number4
DOIs
StatePublished - Oct 2010
Externally publishedYes

Keywords

  • Biochemical conversion
  • Fossil fuel consumption
  • Greenhouse gas emission
  • Life cycle assessment
  • Lignocellulosic ethanol
  • Thermochemical conversion
  • Water consumption

ASJC Scopus subject areas

  • Global and Planetary Change
  • Ecology
  • Pollution

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