Land Conversion May Be Overstated

Scientists Point to 'Faulty' Data in EWG Study

Todd Neeley
By  Todd Neeley , DTN Staff Reporter
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Land-use conversion is considered to be a critical factor in determining ethanol's carbon footprint. (DTN file photo)

OMAHA (DTN) -- Claims by a recent Environmental Working Group study that cutting the Renewable Fuels Standard would reduce carbon dioxide emissions are being challenged by a group of scientists and economists who say the analysis may have overstated the amount of grasslands and wetlands converted to corn crops for ethanol.

At the end of May, the EWG released a report, "Ethanol's Broken Promise: Using Less Corn Ethanol Reduces Greenhouse Gas Emissions." EPA is expected to release RFS volume requirements this summer that reduce the overall mandate for blending biofuels below the volumes currently mandated by law. EWG argues that cutting corn-based ethanol in the 2014 Renewable Fuel Standard by 1.39 billion gallons would reduce carbon dioxide emissions by 3 million tons.

The back and forth over studies measuring marginal changes in land use and carbon footprint reflects the political high stakes in the ethanol industry as the Environmental Protection Agency prepares to release the 2014 volume levels for the Renewable Fuels Standard. EPA is expected to lower the levels for cellulosic and advanced biofuels, but the ethanol industry is arguing EPA should avoid any reduction in the RFS. The EPA announcement is expected soon.

The EWG study said the RFS corn ethanol mandate had "driven up food prices, strained agricultural markets, increased competition for arable land and promoted conversion of uncultivated land to grow crops." The report said previous estimates have "dramatically underestimated corn ethanol's greenhouse gas emissions by failing to account for changes in land use."

An analysis released Wednesday was authored by researchers in the energy systems division at Argonne National Laboratory, as well as professors at the University of Illinois at Chicago, Purdue University's college of agriculture and North Carolina State University's department of agricultural and resource economics. The researchers said that EWG's claims that some 8.1 million acres of grass and shrub lands were converted to corn crops between 2008 and 2012 may be overstating land-use conversion.

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It should also be noted that groups such as American Farmland Trust calculate that the country loses 1.5 million acres of farmland every year to development. Thus, as much as 7.5 million acres of cropland could have been lost from 2008 to 2012.

Land-use conversion is considered to be a critical factor in determining ethanol's carbon footprint. The EWG's conclusion was based on an examination of USDA cropland data layer and satellite data.

"The land areas EWG estimated to have been converted to wetlands and grasslands are high compared to earlier detailed studies and modeling results," the group of scientists said in its analysis. "Further, the emission factors they applied are high compared to those in other reports and studies that take into account important variations in initial and final land states."

The scientists said the emission factor EWG applied to wetland-to-corn conversion "reflects emissions from conversion of peat- and carbon-rich tropical wetlands rather than from conversion of temperate wetlands found in the United States. Conversion of U.S. temperate wetlands should be less carbon-intensive."

The scientists said EWG used EPA's land-use change GHG emissions results for corn ethanol for 2012 to calculate "high life-cycle GHG emissions" for corn ethanol.

"In their report, EWG picked the EPA 2012 GHG emissions for corn ethanol and applied them to the EPA-proposed reduced volume for corn ethanol in 2014 to make the erroneous conclusion that the proposal resulted in 3 million tons of CO2 reduction in 2014," the scientists said.

The EWG study used a "pixel-by-pixel" examination of satellite photos. Still, EWG acknowledged the group may have overestimated land conversion. The scientists said in their analysis that national land cover data developed by the U.S. Geological Survey, however, "is explicitly not designed to be used for pixel-by-pixel or localized analyses."

Read the new analysis here: http://tinyurl.com/….

Read the EWG study here: http://tinyurl.com/….

Todd Neeley can be reached at todd.neeley@dtn.com

Follow Todd on Twitter @toddneeleyDTN

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Todd Neeley

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