Peer reviewers question EPA emission estimates for palm oil
Source: Amanda Peterka, E&E reporter • Posted: Wednesday, January 7, 2015
But two other reviewers suggested the agency may have lowballed emission estimates because of uncertainties in its data.
EPA, which published the peer review last month, said its results would figure into an evaluation of whether palm oil biodiesel and renewable diesel should qualify for RFS credits.
“We will continue dialogue with government, industry, civil society and scientific experts to understand all of the technical issues,” EPA said.
The standard requires EPA to evaluate greenhouse gas emissions of new biofuels before refiners can use them to meet their annual RFS obligations. A new biofuel is allowed to qualify only if it reduces emissions by at least 20 percent from a petroleum fuel base line.
In its 2012 assessment, EPA found that neither palm oil biodiesel nor renewable diesel would meet the 20 percent threshold. Palm oil biodiesel would result in life-cycle greenhouse gas emission reductions of 17 percent and renewable diesel 11 percent, the agency said.
EPA said several factors would contribute to high emissions for palm oil biofuels. Among them was the expected expansion of palm oil plantations onto carbon-rich peat soils in Southeast Asian countries such as Indonesia and Malaysia. The agency estimated that draining tropical peatlands would result in 95 metric tons of carbon dioxide-equivalent emissions per hectare of drained peat soil.
An independent firm organized the peer review for EPA. The five reviewers were Scott Bridgham of the University of Oregon; Kristell Hergoualc’h of the Center for International Forestry Research; Monique Leclerc of the University of Georgia; the president of the Indonesian Peat Society, Supiandi Sabiham of Bogor Agricultural University; and Arina Schrier of the firm Climate and Environmental International Consultancy.
Three of the five reviewers stated that EPA had chosen an appropriate estimate of emissions from drained peatlands, but Leclerc and Schrier raised concerns that uncertainties in the data could lead to an increase in life-cycle emissions estimates.
Two reviewers disagreed. Hergoualc’h and Sabiham found that EPA’s figure overestimated emissions from peatland expansion.
They recommended a peat soil emission factor in the range of 40 metric tons of carbon dioxide-equivalent emissions per hectare of drained peat soil — a figure similar to the most recent recommended emissions factor published by the U.N. Intergovernmental Panel on Climate Change and other studies.
“The emission factor that the EPA proposes to adopt is based on a single study and thus definitely does not meet the ‘representativeness across Southeast Asia’ criterion,” Hergoualc’h wrote.
Environmental groups have criticized the 2013 IPCC estimates of emissions tied to digging up peat soils for palm oil operations, arguing that emissions are at least twice as high. They’ve pointed to massive amounts of deforestation in areas where palm oil plantations are prevalent (ClimateWire, Nov. 18, 2013).
One reviewer, the University of Georgia’s Leclerc, also specifically recommended against the IPCC number.
“This estimate is likely to be too low,” she said. “It is based on earlier, older literature data and also does not recognize the many factors outlined in the present review.”
Although EPA’s initial 2012 analysis shut out palm oil biofuels from the RFS, the issue has remained controversial, with palm oil interests in Southeast Asia urging the agency to allow the fuels to qualify. The questions raised by the peer reviewers over EPA’s analysis are likely to drive continued debate.
“This review report shows that there is indeed a lack of consensus in the scientific community about the magnitude of the emissions from drained peatlands,” said Louis Verchot, research director for forests and environment at the Center for International Forestry Research.
EPA said it “will consider the peer review results along with the public comments received.”
“The agency,” EPA added, “will also continue to evaluate new data and scientific analysis of other important factors in the lifecycle analysis of palm oil biofuels, including deforestation and methane emissions.”