The single year of carbon emissions is the equivalent to the annual greenhouse gas emissions of 951,600 passenger vehicles, according to the EPA’s equivalency calculator. Overall findings of the analysis are based on peer-reviewed, published research that shows that greenhouse gas emissions from ethanol are close to one-third lower than those from gasoline.

A total of 17.5 billion gallons of ethanol would be blended with gasoline by 2016, 3.75 billion fewer gallons than originally mandated by Congress.

The ERC submitted a summary of the analysis to the EPA during one of the pubic hearings on the proposal.

The RFS has been one of the most successful federal policies enacted in the United States because it achieved exactly what it was intended to do: spur research and investment, lower greenhouse gas emissions and reduce dependence on foreign oil. Our work has demonstrated that, over the last 10 years, steady reductions in greenhouse gas emissions have materialized as biofuels became a more efficient, high quality product.

—Dr. Steffen Mueller, principal economist at the Energy Resources Center

(Dr. Mueller served on the Expert Working Group for the California Low Carbon Fuel Standard development and is the co-author of the CCLUB land use interface model to the Argonne GREET model.)

The peer-reviewed analysis was conducted using the GREET Model (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) developed by Argonne National Laboratory which examines the full life cycle emissions impacts of energy sources. As part of the analysis, carbon emissions related to the planting, growing, harvesting, transportation and production of corn into ethanol were compared to that of oil recovery and production.

In supporting information provided for the testimony, the ERC noted that new processing technologies as well as updated life cycle models and databases accessed by computable general equilibrium models have significantly advanced the assessments of the carbon intensity (CI) of biofuels over the last 10 years. For corn ethanol, for example, the following research updates have occurred:

• Land Use Change Carbon Emissions. Published studies on LUC emissions have shown a significant reduction in the predicted carbon emission magnitude over time. This downward trend in predicted emissions is due to several factors in improved CGE models including 1) an evolving understanding of the elasticity of land transitions and yield-price relationships, 2) better addressing of ethanol co-product substitutions in animal feed markets, 3) better understanding and data availability of global land types, and 4) carbon adjustments during land transitions.

  Predicted Land Use Change emissions by different studies over time. Source: ERC. Click to enlarge.

• Technology Innovation at the Biorefinery. The use of fossil energy at the biorefinery is a significant contributor to the CI of ethanol. Published surveys of the ethanol industry showed that 2008 ethanol plants use 30% less energy to convert corn to ethanol than 2001-era plants. A recent follow up survey showed further energy reductions.

• 3)Technology Innovation in Feedstock Agriculture. Emerging agricultural practices and technologies have been shown to further reduce land demands and emissions from biofuels production. Most noteworthy are applications of nitrification inhibitors which stabilize nitrogen fertilizer inputs (a market that has seen 20% year over year growth for the last 5 years), advanced hybrid seeds, and precision agriculture.

• Updated Modeling. The Argonne CCLUB greenhouse gas emissions model from biofuels production incorporates detailed carbon stock factors for different ecosystems that enable an exhaustive analysis of carbon emissions and sequestration from LUC. For selected modeling runs (that take realistic, projected crop yield increases into account) the LUC emissions in CCLUB for corn ethanol total 7-9.0 gCO₂e/MJ (as opposed to 28 gCO₂e/MJ used by EPA for corn ethanol).

Resources

• Mueller, S. (2010) “2008 National dry mill corn ethanol survey.” Biotechnology Letters, 32, 1261-1264 doi: 10.1007/s10529-010-0296-7

• Mueller, S. and John Kwik (2012) “Corn Ethanol: Emerging Plant Energy and Environmental Technologies,” available at www.erc.uic.edu

• Ho-Young Kwon, Steffen Mueller, Jennifer B. Dunn, Michelle M. Wander (2013) “Modeling state-level soil carbon emission factors under various scenarios for direct land use change associated with United States biofuel feedstock production,” Biomass and Bioenergy doi: 10.1016/j.biombioe.2013.02.021

• Jennifer B Dunn, Steffen Mueller, Ho-young Kwon and Michael Q Wang (2013) “Land-use change and greenhouse gas emissions from corn and cellulosic ethanol,” Biotechnology for Biofuels 6:51 doi: 10.1186/1754-6834-6-51