California regulators, trying to assess the true environmental cost of corn ethanol, are poised to declare that the biofuel cannot help the state reduce global warming.



As they see it, corn is no better – and might be worse – than petroleum when total greenhouse gas emissions are considered.



Such a declaration, to be considered later this week by the California Air Resources Board, would be a considerable blow to the corn-ethanol industry in the United States.



If passed, the measure could serve as a model as other states and the federal government tackle carbon emissions. But California's regulators say they have no choice.



The state must assess the full climate change impact of corn ethanol under a California law requiring a sharp cut in carbon emissions from transportation fuels. The board must encourage the use of cleaner alternatives like electricity, hydrogen and cellulosic ethanol, said board spokesman Dimitri Stanich.



The proposal would work like this: If increased production of corn-based ethanol in the U.S. raises corn prices and accelerates the conversion of rainforests and conservations lands to farmland worldwide, greenhouse emissions and loss of the carbon sink associated with such deforestation and disruption must be counted towards the biofuel's total emissions.



"Losing a carbon sink would defeat the purpose of this regulation to reduce greenhouse emissions," Stanich said.



The regulation is part of California's low-carbon fuel standard to reduce greenhouse emissions from transportation fuels by an average of 10 percent by 2020 or 16 million metric tons of carbon emissions over the next decade.



A regional low carbon fuel standard has also been adopted by eleven northeast and Mid-Atlantic states. And President Obama has called for a national low carbon fuel standard. Both efforts are likely to look at California's findings as a model.



Federal law requires U.S. transportation fuels contain 36 billion gallons of renewable fuel by 2022, of which 21 billion gallons must be cellulosic ethanol.



But an overwhelming majority of ethanol mixed into gasoline today comes from corn. By 2012, about a third of all corn produced in the U.S. will go towards making ethanol, according to the U.S. Government Accountability Office. Proponents say this will create thousands of jobs while reducing carbon emissions.



They fear California's rule could stymie that, creating an unfair playing field that only penalizes biofuel production.



"We strongly support the low carbon fuel standard," said Roger Salazar, spokesman for Growth Energy, an ethanol advocacy group. "But the science behind (California's proposal) is extremely uncertain."



More than 100 scientists researching biofuel production agree, having signed a letter to California Gov. Schwarzenegger calling the policy misguided and based on limited scientific models that improperly punish corn-based biofuel.



"Results from the model have not been verified enough to be useful," said Harvey Blanch, a professor of biochemical engineering at University California, Berkeley, and one of the signatories. "There needs to be more studies validating this method before applying it to a legal framework."



This is the first piece of regulation to account for such so-called "indirect land-use effects" of corn-based ethanol. But it is the latest in an ongoing debate about the fuel's effectiveness to reduce greenhouse gases.



Prior research has shown converting corn to ethanol leads to more clearing of rainforests that would do little to slow global warming. A recent study looking at the total climate change and health costs from fuels found that corn-based ethanol equals or exceeds the costs of gasoline. That study, published February in the Proceedings of the National Academy of Sciences, concluded that the combined climate-change and health costs are $469 million for gasoline, $472 million to $952 million for corn ethanol, and $123 million to $208 million for cellulosic ethanol.



Whereas corn ethanol is produced from the edible corn grain, cellulosic ethanol comes from wood, grasses and the non-edible parts of plants. Cellulosic emits fewer greenhouse gases than corn and has minimal impacts on deforestation rate, air pollution and food prices.



"If we are going to be using corn-ethanol in any large quantities, we really need to be sure it is having its intended effects," said Jason Hill, a research associate in applied economics at the University of Minnesota and lead author of the PNAS study.



Including indirect land-use change is essential, Hill said, especially if policies aim to reduce greenhouse gas emissions.



But federal policy is moving in an opposite direction. Pushed by industry and the U.S. Department of Agriculture, the U.S. Environmental Protection Agency is considering upping the percentage of ethanol in the nation's gasoline from 10 percent to 15 percent. All of that, at least in the near-term, would likely come from corn.



California's rules, Salazar said, will scare off investors and the investments needed to make biofuels viable, causing more use of oil. To continue advancements towards cellulosic ethanol – which reduces greenhouse emissions by 90% compared to gasoline – and make it more cost competitive, continued investment in corn ethanol is necessary, he said.



"You can't really get to the ultimate goal of cellulosic without this corn ethanol bridge," he said.

Hill countered that the ethanol industry has grown so fast that it has outpaced the science. The need for precaution is necessary, he said.



"If we are going to have policies to reduce greenhouse gas emissions, the burden of proof should be on the fuels to fulfill that policy," Hill said.



"Right now, there is no clear data that shows corn ethanol has the effect of reducing greenhouse gas emission."

This article originally appeared at The Daily Climate, the climate change news source published by Environmental Health Sciences, a nonprofit media company.