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Renewable Fuel Standard has cut GHG emissions by nearly a billion tonnes

A new analysis from carbon accounting firm Life Cycle Associates LLC has found that the greenhouse gas (GHG) emission reductions achieved under the Renewable Fuel Standard in the United States (US), far exceed the reductions originally projected by US Environmental Protection Agency (EPA). Between 2008 and 2020, the use of biofuels under the RFS has resulted in cumulative savings of 980 million metric tonnes of carbon dioxide-equivalent (CO2eq) GHG emissions.

The avoided GHG emissions are calculated from the reduction in CI from the revised petroleum baseline, as developed by Boland et al. (Boland, 2014). Figure 4 (above) shows the total CO2 savings, in million metric tonnes per year from the inclusion of ethanol, the largest biofuel, in the RFS2. The effect of different levels of E15 in 2025 is also examined using the approach outline previously assuming that 50% is blended at 87 octane and the balance results in higher octane fuel. 51% E15 in a gasoline pool of 138 billion gallons per year could be achieved with the current corn ethanol capacity in the U.S. of 17.4 6 billion gallons per year. Note that the scenario for E15 shown here for 2025 uses more than the 15 billion gallons of D6 ethanol required under the RFS2. E15 results in additional GHG reductions because more ethanol is consumed as fuel and it enables the production of a lower octane BOB (graphic courtesy Life Cycle Associates).

The research, which updates the results from a previously published study, was conducted for the Renewable Fuels Association (RFA) by Stefan Unnasch and Debasish Parida of Life Cycle Associates.

The Renewable Fuel Standard has been the single most effective and efficient policy we’ve ever had for decarbonizing our nation’s transportation fuels. This research clearly demonstrates that the RFS has already put us firmly on the path toward net-zero GHG emissions by mid-century, and the program will continue to serve as the bedrock for future efforts to combat climate change. The RFS has overachieved its original expectations, and renewable fuel producers and farmers across the country should be extremely proud of their important role in securing 1 billion metric tonnes of carbon reduction, said RFA President and CEO Geoff Cooper.

The greater-than-expected GHG savings are attributable to several factors:

  • corn ethanol provided larger GHG reductions than anticipated by EPA;
  • the actual carbon intensity of gasoline and diesel was worse than estimated by EPA;
  • the use of biodiesel and renewable diesel exceeded EPA’s original expectations.

According to the report, “GHG Emissions Reductions due to the RFS2- A 2020 update“, the carbon intensity (CI) of corn-based ethanol used toward the RFS is now 45 percent below the carbon intensity of gasoline, having dropped 20 percent between 2008 and 2020.

The authors attribute ethanol’s shrinking carbon footprint primarily to improvements in the corn ethanol production process, growth in the use of low-carbon biogas as the process fuel, and the elimination of coal as a thermal energy source for dry mill ethanol plants.

Cooper noted that the Life Cycle Associates study is consistent with recently released research from Environmental Health & Engineering Inc. (EH&E), which showed that GHG emissions for ethanol are 32 percent to 62 percent lower than gasoline, with a central best estimate of 46 percent.

In addition, the assessment showed that carbon emissions from converting prior land uses to corn farming make up only 7 percent of the biofuel’s total GHG emissions—a much smaller amount than generally recognized.

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