Some production methods for corn ethanol may increase indirect greenhouse gas (GHG) emissions, according to an analysis unveiled Tuesday by the U.S. Environmental Protection Agency.
The agency analyzed different pathways for generating ethanol, calculating the greenhouse gas emissions through the fuel’s entire lifecycle and compared the results to the baseline lifecycle of gasoline or diesel.
Analysis by the EPA found that corn ethanol produced in a coal dry mill plant increased GHG emissions by 13 percent over a period of 100 years.
However, using a natural gas dry mill plant to produce ethanol reduces emissions by 16 percent over a period of 100 years, and processing it in a best case natural gas dry mill reduces emissions by 39 percent.
Also if a biomass dry mill plant is used to make corn ethanol the process cuts emissions by 39 percent over 100 years. If generated using a biomass dry mill with combined heat and power, GHG emissions are cut by 47 percent.
[T]here are things that can be done to make corn ethanol more sustainable, Lisa Jackson, an EPA administrator said today in a conference call with reporters.
In some pathways, the EPA analysis found that ethanol does not meet the required standards for biofuels established by the Energy Independence and Security Act of 2007.
The ethanol industry has questioned the validity of the findings, claiming that the indirect effect of ethanol's production has been miscalculated.
The science of market-mediated, secondary impacts is very young and needs more reliance on verifiable data, and less reliance on unproven assumptions. Done correctly, such an analysis will demonstrate a significant carbon benefit is achieved through the use of ethanol from all sources, said Bob Dineen, President and CEO of the Renewable Fuels Association.
The EPA says the analysis it presented is a proposal which is open for public comments.
The ethanol industry plans to participate in a discussion of the indirect impacts of all fuels, according to Dinneen. The EPA's period for public discussion will last for 60 days.