Biofuels advocates on Friday tried to debunk a widely reported Science magazine study that found that corn-based ethanol production in the U.S. actually worsens global warming.
The Renewable Fuels Association publicized a paper published by biomass experts at the Argonne National Laboratory's Transportation Technology R&D Center, in which researchers poked holes in the Science study that was published last Friday.
The original study published in Science found that most models that measure the greenhouse gas impact of biofuels do not take into account land use.
The researchers calculated the effect of emissions from converting existing farmland to energy crops and from clearing formerly uncultivated land, such as forests or grasslands, for biofuels.
They concluded that the net effect of corn ethanol production in the United States, when changes in land use are figured in, is more carbon dioxide in the atmosphere. (To dig into the details, click on this PDF.)
The Argonne National Labs responded to the study by finding fault with some of its assumptions.
The Argonne study said that the Science article authors' models were flawed because they did not factor in changing crop yields, which increase every year.
There have been consistent reports of forests in Asia and South America being cut down to grow palm oil trees and other energy crops.
But the Argonne study doubted whether the United States' pro-biofuels policies caused these land-use changes in other countries. That's because it found that exports of corn for food from the U.S. have remained roughly steady in the past few years while corn ethanol production has shot up.
Its overall conclusion: "While scientific assessment of land use change issues is urgently needed in order to design policies that prevent unintended consequences from biofuel production, conclusions regarding the GHG (greenhouse gas) emissions effects of biofuels based on speculative, limited land use change modeling may misguide biofuel policy development."
Pacific Ethanol on Friday issued its own release touting the Argonne study, adding that the science researchers also did not take into account the full environmental impact of oil extraction.
The response caps off a week where biofuels have come under siege, prompted by media coverage of the Science study.
Until now, environmentalists and academics have said that corn-based ethanol produces roughly the same, or slightly less, greenhouse gas emissions as gasoline, when the entire production life cycle is calculated.
The environmental profile of cellulosic ethanol, made from wood chips or perennial grasses, has been found to be substantially better.