Researchers found that existing exceptions for biofuels could lead to deforestation, as seen here in the Amazon rain forest. (Chris Neill/Marine Biological Laboratory)

A group of climate scientists says the Kyoto Protocol has a critical flaw in the way it calculates carbon emissions from biofuels that could undermine the treaty's goal of reducing greenhouse gas emissions.

There is an important, but fixable, error in the way that carbon dioxide emissions from biofuels are exempted from carbon caps, says an article by 13 experts in climate change and land use that goes online this week in Science Express.

This exemption is present in the carbon accounting in the Kyoto Protocol, as well as the European Union's cap-and-trade law and the U.S. Clean Energy and Security Act.

'The error is serious, but readily fixable.'—Timothy Searchinger, Princeton University researcher

The problem, the scientists say, is that tailpipe and smokestack emissions from biofuels are exempt from a country's total carbon emissions, no matter where the biofuels come from. Existing climate laws consider biofuels to be carbon-neutral, regardless of the source.

"The potential of bioenergy to reduce greenhouse gas emissions inherently depends on the source of the biomass and its net land-use effects," the authors write.

Biofuels and fossil fuels emit similar amounts of greenhouse gases when burned, but overall emissions from biofuels may be lower because they come from plants, and plants absorb carbon dioxide as they grow.

However, if a company clear-cuts a forest and burns the trees, fertilizes the land and grows crops from biofuels there, the net emissions of greenhouse gases would be much higher.

Burning trees releases carbon into the atmosphere, just as burning fossil fuels does, and the nitrous oxide released from chemical fertilizers is also an important greenhouse gas.

The study found that carbon emissions from displacing food crops or pastures to grow biofuels may be twice as great as those from land dedicated to bioenergy production.

"When forests or other plants are harvested for bioenergy, the resulting carbon release must be counted either as land-use emissions or energy emissions," said Jerry Melillo, one of the authors of the study.

"If this is not done, the use of bioenergy will contribute to our greenhouse gas problem rather than help to solve it," said Melillo, a researcher at the Marine Biological Laboratory in Woods Hole, Mass.

Biofuels must be properly evaluated: prof

The authors of the report cite a number of studies, including one by the U.S. Department of Energy, that say applying this biofuels exemption worldwide could lead to deforestation as countries try to reach their carbon targets.

"The error is serious, but readily fixable," said Timothy Searchinger, a researcher and lecturer in public and international affairs at Princeton University. Searchinger was not one of the authors of the report.

The report recommends counting all emissions from burning fuels and developing a system to apply carbon credits to biofuels to the extent that they actually offset the emissions, rather than exempting them completely.

The report was published in anticipation of the Copenhagen summit on climate change in December.

"As we approach the most important climate treaty negotiations in history, it is vital that technologies, such as biofuels, that are proposed as solutions to global warming are properly evaluated," said team member Daniel Kamm, a professor of energy and resources at the University of California, Berkeley.