An important but fixable error in legal accounting rules used to measure compliance with carbon limits for bioenergy could undermine efforts to reduce greenhouse gas emissions by encouraging deforestation, according to a new study by 13 prominent scientists and land use experts published in the Oct. 23 issue of the journal Science.
The error affects the Kyoto Protocol and the European Union's Emissions Trading System, and is written into a U.S. climate change bill, the American Clean Energy and Security Act, passed by the U.S. House of Representatives in June.
Tim Searchinger, a research scholar in the Princeton Environmental Institute and a fellow with the German Marshall Fund of the United States, is lead author of the study. Michael Oppenheimer, director of the Program in Science, Technology and Environmental Policy and professor of geosciences and international affairs in the Wilson School of Public and International Affairs, is a co-author.
In the study, "Fixing a Critical Climate Accounting Error," the authors contend that across-the-board exemption of carbon dioxide (CO2) emissions from bioenergy -- the use of plant materials known as biomass for the production of renewable fuels -- is improper in greenhouse gas regulations if emissions due to land-use changes also are not included. This, they assert, erroneously treats all uses of bioenergy as carbon-neutral, renewable energy regardless of the source of the biomass, and could create strong economic incentives for large-scale land conversion as countries around the world tighten carbon caps.
According to the researchers, the greenhouse gas consequences of using bioenergy vary greatly depending on the source of the biomass. For example, if plant growth increases to produce bioenergy, as when fast-growing trees or grasses are grown on degraded land, bioenergy reduces global warming because the plants absorb more carbon from the atmosphere, which offsets the CO2 emitted by burning the bioenergy.
However, if bioenergy use results from burning wood chips from existing forests for electricity, or clearing rain forests to grow palm oil and other crops for biofuels, bioenergy does not reduce greenhouse gas emissions, and instead may increase them. Thus, the accounting rules in these legal measures mistakenly exempt the CO2 emitted by bioenergy regardless of the source, according to the authors.
Neither the Kyoto Protocol, nor the existing or proposed climate legislation in Europe and the United States, currently applies limits to emissions from land use such as deforestation. Because of that, the exemption of the CO2 actually emitted from the burning of biofuels and wood for electricity means all forms of bioenergy are treated as carbon neutral, which creates incentives to clear land.
"The error is serious, but fixable," Searchinger said. "The solution is to count all the pollution that comes out of tailpipes and smokestacks whether from coal and oil or bioenergy, and to credit bioenergy only to the extent it really does reduce greenhouse gas emissions."
This loophole gives oil companies, power plants and industries that face tighter pollution limits a cheap, yet erroneous, means to claim reductions in greenhouse gas emissions. According to a number of studies, including one by a U.S. Department of Energy lab, applying this incentive globally could lead to the loss of most of the world's natural forests as carbon caps tighten.
"The error results from misapplying principles set out by the international scientific body that advises governments on climate change," explained Steve Hamburg, chief scientist at the Environmental Defense Fund, a study co-author and a lead author of the Intergovernmental Panel on Climate Change's year 2000 report on land use. "The accounting rules need to work differently for laws and treaties that limit emissions only from energy use than they work for reporting requirements that apply to emissions both from energy and land use activities."
"Just like with financial audits, it's important for carbon audits to be correct from the start," said Michigan State University professor and study co-author Philip Robertson. "The promise of cellulosic biofuels is huge for our climate and economy. We don't want to find out later that we've built a new industry on a house of cards."
Copies of the article may be obtained by e-mailing scipak@aaas.org.
Tim Searchinger, Princeton University, (202) 465-2074, tsearchi@princeton.edu.
