The U.N. Intergovernmental Panel on Climate Change has for the first time acknowledged the risks of uncontrolled biofuels development, a skepticism that has slowly emerged into the mainstream scientific community, say academics.

IPCC's Working Group II report, released this morning in Yokohama, Japan, indicates that the U.N. scientific body on climate change has loosened its 2007 position that defines biofuels as a mitigation strategy for reducing greenhouse gas emissions.

The report affirms that the science that has raised questions around the sustainability of biofuels in the last six years, said Jeremy Martin, a senior scientist in the Union of Concerned Scientists' Clean Vehicles program.

"I think that's switched from being something novel and controversial to something that is common sense," he said.

A table from the report was leaked last week in which authors list the potential negative risks of development. These issues include indirect land-use change, the conflicts between land for fuels and land for food, water scarcity, loss of biodiversity and nitrogen pollution through the use of excess fertilizer.

Sixty-two countries have biofuel targets or mandates. Environmental and anti-poverty groups like Oxfam and the Environmental Working Group have long opposed biofuel mandates because the groups believe they push up prices for food. Government-backed biofuel programs allow fuel crops to compete with food crops for resources like water and land, they say.

Although Martin is conscious of biofuels' potential to compete for land and emit pollution, he does not reject them outright. He is supportive of the federal renewable fuel standard, the United States' biofuel mandate to produce 36 billion gallons per year by 2022, and has backed the expansion of E85 pumps, stations that supply 85 percent ethanol fuel.

"It would be a mistake to read this report as a repudiation or an about-face," he said. "Biofuels are not going to go away, so rather than looking for a thumbs-up/thumbs-down assessment, policymakers need to be smart about the scale and specific sources of biofuels when they make and implement policies to reduce impacts and manage risks."

Questioning biofuels' ability to curb climate change

But even scientists who view biofuels as generally good have reservations about broad policies that promote bioenergy. A recent report from the International Council on Clean Transportation found that the resources to make biofuels—energy crops like wood, grasses and corn, plus wastes like agricultural residues and household trash—are significantly less than what the IPCC and the International Energy Agency have estimated. While official ranges for biofuel potential up to 2050 range from 500 to 1,500 exajoules per year, the ICCT places that number much lower, between 60 and 120 exajoules per year. (An exajoule equals 1 quintillion joules.)

"A common problem with much of the associated long-term government and research modeling is that it assumes practically unlimited potential for biofuel production. But biofuel potential isn't really a limitless panacea to be accepted simply by assumption," said Stephanie Searle, a researcher at ICCT and the lead author of the report.

Jeffery Greenblatt, a staff scientist at Lawrence Berkeley National Laboratory, agrees that there are simply not enough resources for large-scale policy on biofuels.

"There's not enough biomass supply to provide all of the transportation fuels that we would need," he said. "That's already assuming that we would have a very cost-effective, high-efficiency process for converting raw biomass into finished fuels using a variety of different starting materials."

John DeCicco, a professor at the University of Michigan's Energy Institute, has long questioned the validity of biofuels as a climate mitigation strategy. His next paper, currently under peer review, is a survey of about 100 studies on their life-cycle analyses. He finds that research on how biofuels relate to climate change has been evolving over the last few years.

The IPCC's findings represent a change around the understanding of biofuel science since 2007.

"It's a potential shift in the prevailing view in the climate community," said DeCicco.

Debate continues over impacts on food prices

In 2011, the IPCC wrote a report on renewable energy. Although the report warned governments to avoid the negative effects of bioenergy, it still adhered to a "conventional" positive view, said DeCicco.

"It was generally positive, but guarded," he said. "It wasn't ducking the issue, but it certainly didn't characterize them as a risk mitigation strategy."

The United Nations, however, is less shy of criticizing the fuels. It released a report last year that linked development to rising food prices (Greenwire, Oct. 7, 2013).

Many biofuel critics, like Oxfam, have based their criticism on a 2008 Science paper on indirect land-use change written by Timothy Searchinger. Indirect land-use change is a phenomenon in which changing land use, like converting a field into a cornfield for ethanol, will have an indirect effect elsewhere in the world. Less room for food crops in the United States could increase the demand for agriculture in Brazil, leading to the clearing of rainforest, for example.

Industry groups have rejected this theory, calling it vague and unfounded. Although the European Union doesn't yet include indirect land-use change in its assessment of biofuels, U.S. EPA has used it since 2010 (ClimateWire, July 12, 2013).

The 2008 Searchinger paper triggered more research in the area of land-use change and biofuel production, said Jerome Dumortier, an assistant professor in the Indiana University-Purdue University School of Public and Environmental Affairs.

However, not all biofuels are the same, and Searchinger's findings are still debated within the scientific community. Dumortier's own research found that slight changes in the Searchinger paper's assumptions—like future corn yields or the amount of land that would be converted from forests to cropland—could lead to big changes in the outcome.

"I think that people might equate 'biofuels' with 'U.S. corn ethanol' because it has been produced at such a large scale," he said. "So I think that the IPCC takes up the issue of Searchinger, et al., by saying that increases in biofuel production have to be done carefully to avoid negative consequences."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500