Scientists fault green group’s report on GHG emissions
Source: Amanda Peterka, E&E reporter • Posted: Friday, June 13, 2014
In a 13-page rebuttal of the Environmental Working Group report, the scientists said EWG relied on incorrect parameters and misunderstood modeling results to conclude that ethanol released more greenhouse gas emissions than gasoline.
EWG used its report, which was released last month, to urge U.S. EPA to follow through with a plan to lower the renewable fuel standard.
EWG’s estimated greenhouse gas emissions from ethanol “appear too high,” wrote the seven scientists from Argonne National Laboratory; the University of Illinois, Chicago; Purdue University; and North Carolina State University.
The environmental group estimated that EPA’s proposal to lower this year’s ethanol requirement by 1.4 billion gallons compared with the renewable fuel standard’s requirements would reduce emissions by the equivalent of taking 580,000 cars off the road (Greenwire, May 29).
But EWG applied a model that reflects the conversion of carbon-rich peat lands and wetlands to corn crops, rather than the conversion of the temperate wetlands that are found in the United States, the scientists said.
EWG also “misunderstood” EPA’s calculations for greenhouse gas emissions from ethanol between 2012 and 2017 and confused parameters in a life-cycle model developed by Argonne National Laboratory with those in an economic model, the rebuttal says.
The scientists also said EWG used data to estimate land-use changes associated with ethanol production that were decades old.
Emily Cassidy, biofuels research analyst at EWG, defended the analysis in an email to E&ENews PM. She said the group’s land conversion data was corroborated by an American Farm Bureau Federation report and that applying appropriate land-use changes to EPA’s life-cycle model results in greenhouse gas emissions for ethanol that are greater than gasoline.
“Based on EPA’s 2012 emissions analysis, EWG clearly showed that corn ethanol is worse for the climate than gasoline,” Cassidy said.
The scientists, though, took issue with EPA’s life-cycle analysis, calling it outdated and relying on old assumptions about land-use change associated with ethanol.
“Since 2009, when EPA conducted corn ethanol [land-use change] GHG modeling … significant efforts have been made to improve economic models and soil carbon models to better estimate biofuel LUC GHG emissions,” their response said. “EPA and other federal agencies should consider updating RFS LUC modeling so that up-to-date LUC results can be used for biofuel policy making.”