Bruce Dale, University Distinguished Professor of Chemical Engineering at Michigan State University, shared this presentation that he gave during a webinar hosted by the North Central Bioeconomy Consortium. In it, he highlights the number of factors in Life Cycle Analysis and Indirect Land Use Change (ILUC) models that produce uncertainty – in other words, if the assumptions or data for these factors change, how much do the results change.
Dale is primarily examining the “carbon debt” concept that was introduced in the February 2008 Science papers by Searchinger and Fargione/Tilman. Dale argues that those papers failed to take into account how land converted to crop production might be managed. Dale recently submitted a paper to Environmental Science and Technology, testing the effect on land use change emissions if crop production is managed in a sustainable manner:
Sustainable cropping management practices (no-till and no-till plus cover crops) reduce the payback period to 2 years for the grassland conversion case and to 14 years for the forest conversion case. It is significant that no-till and cover crop practices also yield higher soil organic carbon (SOC) levels in corn fields derived from former grasslands or forests than the SOC levels that result if these grasslands or forests are allowed to continue undisturbed.”
Aside from assumptions about land management, life cycle analysis can be affected dramatically by changes in the amount and kinds of energy used in the biorefinery. American Fuels recently posted a note about some forthcoming research on the energy balance of biofuel production:
University of Nebraska at Lincoln researcher Kenneth Cassman concluded in a upcoming study that ethanol production has become more energy efficient.
‘Recent research conducted at the University of Nebraska clearly shows that estimates for the energy balance of corn-based ethanol are much more favorable – in fact two to three times more favorable, than previous estimates.’”
Since energy inputs are such a large factor in biofuel production, improvements in efficiency will significantly reduce the life cycle greenhouse gas emissions of biofuels when compared to gasoline.