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Biodiesel may worsen global warming relative to petroleum diesel

Biodiesel may worsen global warming relative to petroleum diesel

Biodiesel may worsen global warming relative to petroleum diesel
April 23, 2007

Biodiesel and petroleum diesel have similar environmental impact

Biodiesel made from rapeseed could increase rather than reduce greenhouse emissions compared to conventional diesel fuels, reports a new study published in the journal Chemistry & Industry. Overall the researchers found that petroleum diesel and rapeseed biodiesel, presently the main biofuel used across Europe, have a similar environmental impact. The results suggest that efforts to mitigate climate change through the adoption of rapeseed biodiesel may be of little use beyond energy security.

Comparing the full lifecycle emissions of greenhouse gases by the two fuels from production through combustion in cars, Eric Johnson, editor of Environmental Impact Assessment Review, and Russell Heinen, Vice President of SRI Consulting, found that “biodiesel derived from rapeseed grown on dedicated farmland emits nearly the same amount of greenhouse gas emissions (defined as CO2 equivalents) per km driven as does conventional diesel.”

They show that about two-thirds of greenhouse gas emissions from rapeseed biodiesel occur during the farming of rapeseed, when nitrous oxide (N2O), which is 200-300 times as potent a greenhouse gas as CO2 otherwise, is released into the atmosphere. In contrast, petroleum diesel releases roughly
85 percent of its greenhouse gas emissions during combustion in a vehicle’s engine, the final use stage.

Biodiesel yield (gallons per acre) of various crops.

The researchers say that the difference may be greater depending on land use.

“If the land used to grow rapeseed was instead used to grow trees, petroleum diesel would emit only a third of the CO2 equivalent emissions as biodiesel,” stated a release from the Society of Chemical Industry, publisher of Chemistry & Industry.

The authors say their study has implications for European policymakers looking to meet binding commitments under the Kyoto Protocol.

“Our study suggests that farmers in Europe who are growing rapeseed for biodiesel might combat global warming in a more effective way, namely by converting those fields into forests and using conventional diesel for fuel,” Johnson told “It also suggests that rapeseed biodiesel does not deliver the global warming benefit over conventional diesel that is so often presumed by EU member states.”

Overall the study found that biodiesel and petroleum diesel have similar environmental impact.

“In addition to our study of global warming, we also compared the two fuels in terms of a range of other environmental impacts — from eco and
biological toxicity to ozone layer depletion and acidification,” the authors wrote. “To do so, we weighted the complete emissions inventories of each system, not just
greenhouse gases, by using a commonly used impact assessment method. The answer is equivocal: petroleum diesel comes out ahead in five categories; biodiesel comes out ahead in the other five.”

Johnson is now looking at the lifecycle climate impact of other sources of biodiesel, like soybeans and oil palm.

“We are studying [palm oil and soybeans] at present and hope to have answers in a few months’ time,” Johnson said. “A key factor here will be – as it was for rapeseed – nitrous oxide (N2O, or laughing gas) emissions from their farming. N2O is a significant global warmer, with a 100-year global warming potential of 296 (carbon dioxide’s GWP is 1). There is much research and debate going on about N2O emissions, and I’m trying to get abreast of it for these other crops.”

Transportation currently accounts for more than a 20 percent of all EU greenhouse gas emissions, according to a statement from the Society of Chemical Industry. The 2003 EU Biofuels Directive seeks to increase the levels of biofuels to 5.75 percent of all transport fuels by 2010 and 10 percent by 2020, up from about 2% today.

Eric Johnson and Russell Heinen (2007). Petroleum diesel vs biodiesel: The race is on. Chemistry & Industry — 23 22 April 2007.


Ethanol may be greener but have higher health cost. Widespread burning of ethanol as fuel may increase the number of respiratory-related deaths and hospitalizations relative to gasoline, according to a new study by Stanford University atmospheric scientist Mark Z. Jacobson. The report comes as mounting environmental concerns cloud the benefits of using ethanol as a green alternative to fossil fuels.

Soybeans may worsen drought in the Amazon rainforest. The rapid expansion of soybean cultivation in the Amazon may be having a larger impact on climate than previously believed, according to research published last week in Geophysical Research Letters. Using experimental plots in the Amazon, a team of scientists led by Marcos Costa from the Federal University of Vicosa in Brazil found that clearing for soybeans increases the reflectivity or albedo of land, reducing rainfall by as much as four times relative to clearing for pasture land.

Palm oil doesn’t have to be bad for the environment. As traditionally practiced in southeast Asia, oil palm cultivation is responsible for widespread deforestation that reduces biodiversity, degrades important ecological services, worsens climate change, and traps workers in inequitable conditions sometimes analogous to slavery. This doesn’t have to be the case. Following examples set forth by the Roundtable on Sustainable Palm Oil and firms like Golden Hope Plantations Berhad, a Malaysian palm oil producer, oil palm can be cultivated in a manner that helps mitigate climate change, preserves biodiversity, and brings economic opportunities to desperately poor rural populations.

U.S. can cut oil imports to zero by 2040, use to zero by 2050. The United States could dramatically cut oil usage over the next 20-30 years at low to no net cost, said Amory B. Lovins, cofounder and CEO of the Colorado-based Rocky Mountain Institute, speaking at Stanford University Wednesday night for a week-long evening series of lectures sponsored by Mineral Acquisition Partners, Inc.

Biofuels demand will increase, not decrease, world food supplies. As concerns mount over fuel-versus-food competition for crops, a Michigan State University ethanol expert says that cellulosic ethanol could render the debate moot. Bruce Dale, an MSU chemical engineering and materials science professor, notes that ethanol can be made from cellulosic materials, like farm waste, instead of corn grain.

This article used quotes an information from “Petroleum diesel vs biodiesel”, a news release from the Society of Chemical Industry, and pesonal correspondence with the authors.

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