While the U.S. and others race to expand the use and production of biofuels, a growing body of scientific evidence suggests these gasoline alternatives will actually boost carbon-dioxide levels.
A study published in the latest issue of Science finds that corn-based ethanol, instead of reducing greenhouse-gas emissions by a hoped-for 20%, will nearly double the output of CO2 and other gases that trap the sun's heat. A separate paper in Science concludes that the clearing of native habitats around the world to grow more biofuel crops will lead to more carbon emissions, not less.
Such findings could spur a big rethink on the purported benefits of biofuels, an emerging field that has already been blamed for pushing up prices of corn and other food crops, as well as straining water supplies. The European Union has proposed that 10% of all fuel used in transport should come from biofuels by 2020. In the U.S., production growth is encouraged both by high oil prices and by the hope that Congress will stiffen current rules mandating that refiners use ethanol.
Scientists have long touted the benefits of biofuels because growing biofuel feedstock would remove greenhouse gases from the air, while gasoline and diesel fuel take carbon from the ground and put it in the air. However, the earlier studies didn't account for one hard-to-measure factor: The decision by farmers world-wide to convert forest and grasslands to grow feedstock for the new biofuels.
Such land-use changes can have big and unintended deleterious effects, such as causing food shortages and harming biodiversity. For example, when forests or grasslands are converted for agricultural use, it leads to a large, quick release of carbon when the existing plant-life is destroyed and the soil is tilled. Even if biofuels are grown on cropland previously used to grow food, farmers tend to then clear other forests and grasslands and grow the food elsewhere. The net result: More CO2 in the atmosphere, not less.
In one of the Science papers, researchers concluded that corn-based ethanol would double greenhouse gases over 30 years instead of leading to an anticipated 20% reduction. "Even if we're dramatically wrong, it's hard to get to a result that says you get a benefit over 50 years," says Timothy Searchinger, a researcher at Princeton University and a co-author of the paper.
In the second study, researchers found that the potential carbon savings of biofuels – or the harm caused by them – varied hugely, depending on where and how they were produced. They calculated that growing sugarcane -- a relatively efficient source of ethanol -- in Brazil's savannah releases 17 times more carbon dioxide than the CO2 that can be saved from burning the biofuel produced on that land each year. At the same time, the draining and clearing of peatlands in Malaysia and Indonesia to grow palm oil releases 420 times more CO2 than the amount saved each year from burning the resultant palm biodiesel.
David Tilman, an ecologist at the University of Minnesota and co-author of the second paper, said the biofuel industry needs to seek out alternative and more efficient sources for biofuels, such as manure and various kinds of waste. A researcher from the Nature Conservancy, an environmental advocacy group, was also a co-author of the study.
Their study's funding came from the U.S. National Science Foundation and the University of Minnesota's Initiative on Renewable Energy and the Environment, according to Mr. Tilman.
The other paper relied on funding from a variety of indirect sources, ranging from the Hewlett Foundation to the U.S. Department of Agriculture.
In response to the papers, the Renewable Fuels Association in the U.S. conceded that "biofuels alone are not the silver bullet" for the world's energy or environmental challenges. The group defended their use, though, saying that analyses of greenhouse-gas reductions from ethanol production show that corn-derived ethanol today reduces greenhouse gas emissions by 22% on average.
"We absolutely assert that ethanol production and use is a responsible way to address the environmental, energy and economic challenges the world faces today," spokesman Matt Hartwig said.
Biofuels can be extremely expensive to produce. A few months ago, Richard Doornbosch, an economist at the Paris-based Organization for Economic Cooperation and Development, caused a stir by questioning whether biofuels could cut greenhouse gases in a cost-effective manner. (Though it was published by the OECD, his study didn't necessarily reflect the views of OECD members.)
In that paper, Mr. Doornbosch noted that it costs more than $500 to avoid releasing a ton of carbon-dioxide by using corn-based ethanol, the main biofuel in the U.S. today. By comparison, tradable emission credits in the European Union are currently priced at less than $30 each. Each allowance carries the right to emit one ton of carbon dioxide.
Scientists are casting doubt on other aspects of the carbon-saving potential of biofuels. A 2007 study, co-authored by Nobel-prize-winning chemist Paul Crutzen, found that fertilizer used to grow corn raised emissions of nitrous oxide, an especially potent greenhouse gas.
From: Feb 7, 2008 Wall Street Journal