Study: Scaling Back Renewable Fuel Standard Will Decrease Greenhouse Gas Emissions

by Marlo Lewis on May 30, 2014

in Blog

In November of last year, EPA proposed to scale back the overall Renewable Fuel Standard (RFS) 2014 blending target from 18.15 billion to 15.21 billion gallons, and to trim the mandate’s corn-ethanol component from 14.4 billion to 13.0 billion gallons. Forcing EPA’s hand was a set of market constraints commonly called the “E10 blend wall.” EPA intervened so that refiners would not be obligated to purchase and blend more ethanol than could actually be sold in gasoline.

The biofuel industry fiercely opposes the proposed cutbacks. EPA is expected to announce the final 2014 RFS production quota in June.

To help EPA stick to its guns, the Environmental Working Group (EWG) yesterday released Ethanol’s Broken Promise: Using Less Corn Ethanol Reduces Greenhouse Gas Emissions. The study estimates that EPA’s proposed 1.39 billion gallon cutback in the corn-ethanol blending target would “lower U.S. greenhouse gas emissions by the equivalent of 3 million tons of carbon dioxide equivalent (CO2e) — as much as taking 580,000 cars off the road for a year.”

EPA can’t dispute this conclusion because the numbers come from the agency’s own data. EPA estimates that, on a life-cycle basis, corn ethanol’s carbon dioxide-equivalent (CO2e) emissions were 33% higher than gasoline’s in 2012.


Since a chief purpose of the RFS is to reduce greenhouse gas emissions, the policy is counterproductive if corn-ethanol emits more CO2e than the gasoline it displaces.

EPA, however, predicts that by 2022, biofuel production will reduce net CO2e emissions by 17%.

Not so fast, says EWG! EPA assumes that by 2022, carbon-neutral biomass will power ethanol plants. It’s more likely that most plants will run electricity from natural gas. More importantly, land-use conversions associated with ethanol production release carbon locked in soils. And, EWG contends, EPA’s analysis “essentially ignored all land use change emissions before 2022.”

EWG estimates that during 2008-2012 alone, RFS-induced land conversions released 85-to-236 million metric tons of CO2e emissions per year.

A previous EWG study found that 23 million acres of U.S. grassland, shrub land and wetland had been converted to crop production between 2008 and 2011. “Eight million acres were converted to grow corn and another 5.6 million to plant soybeans, because the ethanol mandate pushed up soybean prices as well.” EWG research also shows that roughly 306,000 acres of wetlands were converted to corn production between 2008 and 2012. Plevin at al. (2010) estimate the following emission rates from land use changes:

CO2 emissions from land use conversions Plevin et al 2010 per EWG 2014

Multiplying acreage conversions by emission rates gives the following results:

  • Emissions from wetlands conversions between 2008 and 2012 totaled 25-to-74 million tons of CO2e per year.
  • The additional 8 million acres of grasslands and shrub lands converted to corn from 2008 to 2011 added another 60-to-162 million tons of CO2e per year.

In all, land conversions to corn production released 85-to-236 million tons of CO2e per year.

What about the long-term impact of corn ethanol on CO2e emissions? EWG cites an analysis by the Clean Air Task Force. Assuming no cutback in RFS blending targets, cumulative CO2e emissions from corn ethanol during 2010-2044 exceed those from an energy-equivalent amount of gasoline by 28%:

CO2 emissions ethanol vs gasoline 2011-2022









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