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USDA: US corn-based ethanol reduces GHG emissions by 43% compared to gasoline, with additional benefits projected through 2022

A new lifecycle analysis of corn ethanol released by the US Department of Agriculture (USDA) finds that GHG emissions associated with corn-based ethanol in the United States are about 43% lower than gasoline when measured on an energy-equivalent basis. Unlike other studies of GHG benefits, which relied on forecasts of future ethanol production systems and expected impacts on the farm sector, this study reviewed how the industry and farm sectors performed over the past decade to assess the current GHG profile of corn-based ethanol.

The new report, A Life-Cycle Analysis of the Greenhouse Gas Emissions of Corn-Based Ethanol, found greater lifecycle GHG benefits from corn ethanol than a number of earlier studies, driven by a variety of improvements in ethanol production, from the corn field to the ethanol refinery. Farmers are producing corn more efficiently and using conservation practices that reduce GHG emissions, including reduced tillage, cover crops and improved nitrogen management. Corn yields are also improving—between 2005 and 2015, US corn yields increased by more than 10%.

This report provides evidence that corn ethanol can be a GHG-friendly alternative to fossil fuels, while boosting farm economies.

—US Agriculture Secretary Tom Vilsack

Among the findings:

  • Between 2005 and 2015, ethanol production in the US also increased significantly—from 3.9 to 14.8 billion gallons per year. At the same time, advances in ethanol production technologies, such as the use of combined heat and power, using landfill gas for energy, and co-producing biodiesel helped reduce GHG emissions at ethanol refinery plants.

  • By 2022, given current trends, the GHG profile of corn-based ethanol is expected to be almost 50% lower than gasoline primarily due to improvements in corn yields, process fuel switching, and transportation efficiency.

  • If additional conservation practices and efficiency improvements are pursued, such as the practices outlined in USDA’s Building Blocks for Climate Smart Agriculture and Forestry strategy, the GHG benefits of corn ethanol are even more pronounced over gasoline—about 76%.

  • On-farm conservation practices, such as reduced tillage, cover crops, and nitrogen management, are estimated to improve the GHG balance of corn ethanol by about 14%.

GHG balance of gasoline compared to three different corn ethanol scenarios: 1) the lifecycle GHG balance of corn ethanol in 2014; 2) the projection of corn ethanol’s lifecycle GHG emissions in 2022 based on current trends; and 3) the 2022 GHG balance of corn ethanol based on increased agricultural conservation practice adoption, such as the practices outlined in the USDA’s Building Blocks for Climate Smart Agriculture and Forestry strategy. Source: USDA. Click to enlarge.

There are several reasons this report found greater lifecycle GHG benefits from corn ethanol than a number of earlier studies. Previous estimates anticipated that growing corn to produce ethanol would result in indirect land use change—in other words, land would be converted from grasslands and forests to commodity production as a result of increased demand for corn used in ethanol production. But based on new data and research, there is compelling evidence that while land use changes have occurred, the actual patterns of changes and innovation within the farm sector have resulted in these indirect emissions being much lower than previously projected.

Recent studies of international agricultural land use trends show that that the primary land use change response of the world’s farmers from 2004 to 2012 has been to use available land resources more efficiently rather than to expand the amount of land used for farming. Instead of converting new land to production, farmers in Brazil, India and China have increased double cropping, expanded irrigation, reduced unharvested planted area, reduced fallow land and reduced temporary pasture. Much of the international attention on supply of corn for ethanol has focused on Brazil, where earlier estimates anticipated conversion of rainforests to commodity production. But between 2004 and 2012, at the same time US corn ethanol production increased more than 200%, deforestation in Brazil’s Amazon decreased from 10,200 to 2,400 square miles per year.

The report also demonstrates the added GHG benefits of on-farm conservation practices like reduced tillage, nitrogen stewardship, and cover crops—the same practices outlined in USDA’s Building Blocks for Climate Smart Agriculture and Forestry strategy, which aims to reduce GHG emissions by more than 120 million metric tons of carbon dioxide equivalent per year by 2025.

Continuing to support adoption of these practices on farms will further reduce GHG emissions associated with agriculture—as well as benefiting the positive trends in lifecycle GHG balance of corn-based ethanol, USDA said.




The study methodology looks suspect for three reasons: first, ethanol is made by distilling (consumes energy)whereas gasoline is made by catalytic cracking. The yellow bars suggests corn roughly 2x GHC vs gasoline production which does not seem enough. Second, the tailpipe GHG output for the two fuels should be the same or close to the same. Last, they are using '05 tailpipe for gasoline. The GHG has improved by 50% or more since '05, with some vehicles delivered in Europe.


Did corn growers and ICEV makers pay for that study?


USDA Contract
Cellulose ethanol can be even better.


Well, the news I have read had ethanol roughly 50% below gasoline, even with the unfair land use demerit. You do know that other fuels, suffer not, any indirect consequences. No oil wealth demerits for support of tyrants, increased defense needs, or more expense health car. No demerit for super tanker transport upon our oceans and threat of widespread pollution. Same for electric power. No demerit for power line forest removal or coal mining. It is hypercritical to penalize ethanol, when the real stats are proving that efficient farming with the wealth gain at this level is increasing food production as well as minimizing the need of Amazon jungle conversion. To us commoners it makes total sense. You put more money in the pocket of farm business they will buy and educate themselves to be more efficient and productive. No need to cut down the jungle.

Also, within a short time ethanol will be -75% carbon of of plain gasoline. Did you catch the rating as based on equivalent
BTU? That is another injustice as the quality of ethanol fuel belies it's BTU rating. Cummings E85 engine matched the MPG of the comparison current commercial gasoline mid delivery van. So, the -30% decrease per BTU should evaporate once we tune our diesel engines to ethanol. So, within reality we are sitting on a carbon neutral fuel source that will quickly go to negative carbon rating. I don't see the competition catching up. None of them could possible go to negative carbon. You factor in cellulosic that would be basically waste that rating goes very negative carbon. It would be extremely efficient to utilize a pollution source as for fuel. feed stock.


43% lower GHG for ethanol vs gasoline.

Guess what? For biodiesel it is 75%

Dr. Strange Love

It is very reasonable to say that ethanol, biobutanol, biodiesel and perhaps methane derived DME can meet US demand within say 10 years.


This is another lie printed by greencarcongress, climate change proponent.


Take a hike.

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