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New DOE ANL analysis confirms US ethanol’s low-carbon benefits

The carbon footprint of US corn ethanol decreased by 23 percent between 2005 and 2019 as farmers and ethanol producers adopted new technologies and improved efficiency, according to a new analysis by researchers at the US Department of Energy’s Argonne National Laboratory (ANL). By 2019, the researchers found, corn ethanol was reducing lifecycle greenhouse gas (GHG) emissions by 44-52 percent compared to gasoline.

Cumulative GHG emission reduction benefits (area) of the corn ethanol industry from 2005 through 2019 (in MMT CO2e) through CI reduction and ethanol volume expansion, with annual ethanol production (curve). Emission reduction benefits are estimated using the CI in Fig. 4 plus LUC emissions of 7.4 g/MJ from GREET (graphic courtesy ANL).

The researchers also determined that corn ethanol alone reduced transportation-related GHG emissions by almost 550 million tonnes between 2005 and 2019. The findings have been presented in a paper “Retrospective analysis of the U.S. corn ethanol industry for 2005–2019: implications for greenhouse gas emission reductions” and published in the journal Biofuels Bioproducts and Biorefining.

They are also consistent with other research published earlier this year, which found corn ethanol offers an average GHG savings of 46 percent, and the use of all biofuels (i.e., ethanol, renewable diesel, biodiesel, biogas, etc.) between 2008 and 2020 reduced GHG emissions by 980 million tonnes.

Our study shows that while the corn ethanol industry has experienced significant volume expansion, it has reduced the GHG intensity of corn ethanol through improved US corn farming and ethanol biorefinery operations. Corn yield has increased, and chemical and energy use intensities of corn farming have decreased. In ethanol biorefineries, ethanol yield has increased, and energy use has decreased significantly. Biofuels, including corn ethanol, can play a critical role in the U.S. desire for deep decarbonization of its economy, the researchers noted.

Commenting on the new research, Renewable Fuels Association (RFA) President and CEO Geoff Cooper remarked that the new study from the experts at Argonne National Laboratory added to a growing body of scientific evidence that “proves today’s corn ethanol is playing a major role in decarbonizing the nation’s transportation fuels and combatting climate change.”

The researchers found that modern corn ethanol cuts GHG emissions by half compared to gasoline and underscored that the contribution of land-use change to total emissions is estimated to be relatively small, based on real-world experience and empirical data, compared to the levels that had been theorized toward the beginning of the timeframe examined. Continuous improvements in farming and biofuel production technology have helped establish ethanol as a true low-carbon fuel that is available here and now to clean up our nation’s liquid fuels. And, as acknowledged by these researchers, those improvements will continue; with the adoption of new and emerging technologies, we expect corn ethanol can be a net carbon-neutral or carbon-negative fuel by the end of this decade, said Geoff Cooper.

The ANL researchers attribute the improvement in corn ethanol’s GHG performance to efficiency gains in every phase of the fuel’s production lifecycle between 2005 and 2019, including:

  • A 15 percent increase in corn yield per acre;
  • A 7 percent reduction in nitrogen fertilizer use per bushel of corn;
  • An 18 percent reduction in potash fertilizer user per bushel of corn;
  • A 14 percent reduction per-bushel in farming energy use;
  • A 6.5 percent increase in ethanol yield, and;
  • A 24 percent reduction in ethanol plant energy use.

The study concludes that the “reduction in the 58 gCO2e/MJ CI of corn ethanol in 2005 to 45 g/MJ in 2019 (plus the LUC value of 7.4 g/MJ) provides significant GHG emission reductions compared to the CI of 93 gCO2e/MJ for the US average petroleum gasoline blendstock.”

We encourage the White House and Environmental Protection Agency to consider the findings of this study as they examine policy and regulatory opportunities for reducing carbon pollution. We also urge EPA to incorporate the Argonne results and other recent research as the agency considers updating its 12-year old GHG analysis of ethanol and other renewable fuels, said Geoff Cooper.

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