Most folks probably don’t think that power plants burning coal and ethanol — the latter touted as a having a smaller carbon footprint — have much in common. But at least one ethanol plant — Blue Flint Ethanol in Underwood, N.D. — is co-located with a coal-fired power plant in order to use its excess steam heat. And that arrangement could become more common.
However, the history of science is replete with examples of "solutions" turning into new kinds of problems. Such could be the case with ethanol. In a pair of studies that challenge the rush to use biofuels to combat global warming, researchers conclude that converting croplands, forests, or grasslands to grow biofuels to reduce gasoline consumption and address global warming can actually increase net emissions substantially.
One of the studies… concludes that converting lands to produce biofuels creates a "biofuel carbon debt" by releasing 17 to 423 times more CO 2 than the fossil fuels they replace.
The studies, released on the web site of the journal Science (www.sciencemag.org), examined the impacts of converting lands to produce ethanol and biodiesel to cut petroleum use.
One of the studies, undertaken by researchers at the University of Minnesota and the Nature Conservancy, concludes that converting lands to produce biofuels creates a "biofuel carbon debt" by releasing 17 to 423 times more CO 2 than the fossil fuels they replace. Repaying this carbon debt by using the biofuel instead of gasoline or diesel can take decades, or in some cases, centuries, the study concluded.
A separate study by scientists at Princeton University, the German Marshall Fund of the United States, and several other academic institutions found that emissions can increase sharply as farmers around the world respond to commodity price increases and convert forests and grasslands to grow either energy crops or food crops to make up for food production lost when other farmers converted crop lands to grow energy crops.
While earlier studies concluded that biofuels produced from switchgrass or poplar are far superior to corn-derived ethanol in terms of reducing greenhouse gas emissions, the new research shows that using these so-called energy crops can also exacerbate global warming because of the changes in land use they require.
Globally, there is almost three times as much carbon in plants and soil as there is in the atmosphere, and plowing up grasslands and forests to produce biofuel crops releases this CO 2 into the atmosphere. Depending on what crop is used to produce the biofuel, it can take many years of displacing gasoline or diesel to make up the amount of CO 2 released from the soil.
In the worst case examined by the researchers, the carbon debt created by converting tropical peatlands in Indonesia into palm oil plantations would take more than four centuries to pay off by replacing diesel oil with biodiesel. Not far behind is tearing down Amazon tropical forests to grow soybeans for biodiesel, which pays for itself in 319 years, the studies said.
Converting grasslands to grow corn in the U.S. to produce ethanol incurs a carbon debt that takes 93 years to repay, while using abandoned cropland to grow corn for ethanol takes 48 years, the studies concluded. (For more on the food/fuel connection, see the sidebar.)
"The research examines the conversion of land for biofuels and asks the question, "is it worth it?’" said Joe Fargione, a Nature Conservancy researcher and a lead author of one of the two studies. "Surprisingly, the answer is no."
In an online interview with Nature.org, Fargione said the rush to biofuels is actually exacerbating global warming by releasing carbon stored in soils and trees.
"Adding energy production to our current and growing demand for food production inevitably requires more land to be converted to agriculture, whether or not the biofuel is grown directly on that land," Fargione said. "So biofuels either directly or indirectly cause land clearing, which releases carbon to the atmosphere and contributes to global warming. This is the biofuel carbon debt."
Fargione explained that all current biofuel production is a net loser in terms of climate change but noted that biofuels produced from agricultural and forest wastes, and from native grasses and woody plants grown on marginal lands not suitable for other crops, could yield net greenhouse gas benefits. He said that "producing liquid transportation fuels may not be the most efficient way to use the energy contained in biomass," but added that converting biomass into electricity may be its most efficient and economic use.
Many Policy Issues
The Princeton study, led by Tim Searchinger, a research scholar at the university’s Woodrow Wilson School of Public and International Affairs, used a worldwide agricultural model to estimate emissions from land-use change as farmers respond to increases in commodity prices caused by taking crop land out of food production to grow crops for ethanol.
In its main conclusion, the study found that "corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse gas emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%."
The study "raises concerns about large biofuel mandates and highlights the value of using waste products" to produce energy.
The studies call into question the wisdom of legislation enacted last year and signed into law by President Bush to require refiners to include some 36 billion gallons of ethanol in gasoline by 2022, including 21 billion gallons of biofuels produced from feedstocks other than corn.
Corn for Food or Fuel?
"There was once a food economy and an energy economy — but the boom in biofuels is now merging the two," said Phil Humphres, senior specialist – engineering for IFDC, an international center for soil fertility and agricultural development, in the center’s latest North American Fertilizer Capacity report (December 2007).
In the U.S., 70% of corn production has traditionally been used as animal feed, Humphres says. But 18% to 20% of the 2007 U.S. corn crop was used for ethanol, which drove up corn prices 70%. In 2008, 25% of U.S. corn is projected to go into ethanol.
According to the U.S. Department of Agriculture, U.S. corn production in 2007 was 13.1 billion bushels — 24% more than in 2006 and the largest U.S. corn harvest since 1933. Yet the price of corn — traditionally the main ingredient of livestock feed and now the main raw material for U.S. biofuels — rose from $3.05/bushel in January 2007 to $4.28/bushel in January 2008. The price of 1 U.S. gallon of milk also rose from $3.20 to $3.87 in the U.S. between January 2006 and December 2007.
Humphres added, "Prices of products that use corn are rising, and much of the cost will be passed to consumers."
"In the U.S., the government subsidizes ethanol by 51 cents a gallon," Humphres says. "Large companies are contracting corn from farmers who apply more fertilizer to maximize production."
Only meeting the U.S. mandate for biofuel production would require a 60% increase in U.S. land planted to corn, according to the International Food Policy Research Institute.
— Contributed by IFDC (www.ifdc.org)