EPA's RFS accounting shows corn ethanol today is worse than gasoline

As I discussed here, last week’s Congressional Budget Office (CBO) evaluation of the costs and effectiveness of corn ethanol subsidies found that any reduction in greenhouse gas (GHG) emissions we get from replacing gasoline with corn ethanol comes with a massive price tag to U.S. taxpayers. The CBO analysis, however, excluded emissions associated with land use change, which turn out to be substantial and often making corn ethanol more GHG-intensive than the gasoline it replaces. In this blog, I’d like to take a look at how EPA accounts for the emissions associated with corn ethanol.  

Under the 2007 Energy Independence and Security Act (EISA), corn ethanol produced at new plants in the U.S. is required to deliver a 20% reduction in lifecycle GHG emissions relative to gasoline. As the agency responsible for overseeing implementation of this new Renewable Fuel Standard (RFS2), EPA submitted a thorough Regulatory Impact Analysis (RIA) assessing the lifecycle GHG emissions, direct and indirect, associated with corn ethanol and other biofuels, paying special attention to the significant impacts of indirect land use change (ILUC). 

[For a quick recap on the basic dynamics of emissions from ILUC, see this great video]

So does corn ethanol meet this standard? Corn ethanol proponents frequently point to EPA’s finding that the average natural gas-powered drymill plant will produce emissions savings of 21% relative to gasoline, just meeting the target (see chart on page 481 of the RIA), but they gloss over the fact that this is really a forecast of how the industry could perform in 2022, as Richard Plevin of UC Berkeley point out here. This is without a doubt the weakest part of EPA’s RFS2 regulations. Imagine if EPA regulated coal pollution based on how we hoped coal plants would perform 12 years from now? 

What does EPA’s analysis say about the environmental impacts of corn ethanol as it’s produced today? Let’s look into the data.

Here are the projected 30-year average emissions of corn ethanol, assuming 2012, 2017, and 2022 technologies (yellow = an increase in emissions relative to gasoline; orange = a reduction in emissions short of the 20% RFS2 mandate):

Bottom line, while corn ethanol technically can be produced with lower GHG emissions than gasoline today, what the industry is actually producing today is causing more climate pollution than gasoline.

Glossary: DDGS=dried distillers grains & solubles (a type of animal feed coproduct); wet DGS= wet distillers grains & solubles; NG= Natural Gas; CHP=Combined Heat and Power

LC GHG ethanol chart.bmp

In 2012, the vast majority of plants actually show increases in emissions from corn ethanol relative to gasoline. In 2017, the picture improves slightly, though many plants still fail to meet the RFS2-mandated 20% reduction threshold, and most of those that do beat the threshold, just barely make the grade at 21%. In many instances, lifecycle emissions increase.

Only in 2022 do most plants achieve the 20% reduction required by EISA, with only coal-fired dry mills and NG- and coal-fired wet mill plants failing to meet the standard. But as I mentioned, this is based on hypothetical improvements in biofuel performance anticipated 12 years into the future. Should these technologies fail to improve, a decade from now, corn ethanol could continue to pollute more than the gasoline it replaces.

The chart below helps to visualize EPA’s findings:

ethanol chart.bmp

At its worst, lifecycle GHG emissions from corn ethanol exceed those from gasoline in all three scenarios. At its best, corn ethanol is not that much better than gasoline on a climate basis, and certainly not good enough to warrant the soil degradation, water resource depletion and water pollution it continues to cause. What is clear is that rigorously accounting for the carbon in our lands is critical to getting our bioenergy policies right. We need biofuels from feedstocks that don’t compete with our food supply and deliver the GHG emission reductions that move us toward achieving our climate goals. By continuing to subsidize old, polluting corn ethanol, we are diverting billions of dollars from the new, innovative and clean advanced biofuel technologies that really need our support.

This post was co-written with Matt Eisenson.

About the Authors

Sasha Stashwick

Senior Advocate, Energy & Transportation and Food & Agriculture programs

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