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Biofuels Doubts Deepened by US Study
2/11/2008
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New report finds biofuels produce more greenhouse gas than fossil fuels do

by Craig Weatherby


We’re really not trying to make food-based fuels look bad. It’s just that new reports keep questioning the economic and environmental credibility of growing food crops like corn, soy, and sugarcane to make fuel.


Recently, official Swiss and British studies concluded that fuels made from corn, soy, or sugarcane constitute energy-inefficient alternatives that worsen both global warming and environmental destruction on the ground.


See “Corn-Based Fuel Fares Poorly in New Analysis” and  “Biofuels' Downsides Prompt Europeans to Backpedal.


Those reports were largely ignored by the American media, but that’s changed with the release last week of two studies that confirmed their critical conclusions.


The US media paid more attention to the new studies, perhaps because both were published in the prestigious journal Science by researchers from American institutions: Princeton University, Woods Hole Research Center, Iowa State University the University of Minnesota and the Nature Conservancy.


In short, the US-based new studies find that making biofuels from most food crops cause more greenhouse gas emissions than conventional fuels, if you include the processes required to produce ethanol from crops.


It had been assumed that the carbon released when land was cleared to plant crops for biofuel burned was balanced by the carbon absorbed as those crops grew.


But the process of turning plants into fuels involves emissions from refining and transport, among other things.


And one of the studies concluded that clearance of grassland releases 93 times the amount of greenhouse gas that would be saved by the fuel made annually on that land (Fargione J et al 2008).


Here’s how the authors summarized their papers’ conclusions:

  • “Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain (or cropland) diverted to biofuels” (Searchinger T et al. 2008).
  • “Using a worldwide agricultural model to estimate emissions from land use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This result raises concerns about large biofuel mandates and highlights the value of using waste products” (Searchinger T et al. 2008).
  • “Increasing energy use, climate change, and carbon dioxide (CO2) emissions from fossil fuels make switching to low-carbon fuels a high priority. Biofuels are a potential low-carbon energy source, but whether biofuels offer carbon savings depends on how they are produced” (Fargione J et al 2008).
  • “Converting rainforests, peatlands, savannas, or grasslands to produce food-based biofuels in Brazil, Southeast Asia, and the United States creates a ‘biofuel carbon debt’ by releasing 17 to 420 times more CO2 than the annual greenhouse gas (GHG) reductions these biofuels provide by displacing fossil fuels. In contrast, biofuels made from waste biomass or from biomass grown on abandoned agricultural lands planted with perennials incur little or no carbon debt and offer immediate and sustained GHG advantages.” (Fargione J et al 2008)

By “...biomass grown on abandoned agricultural lands planted with perennials...” the authors mean fibrous weeds like switchgrass. Likewise, they find no fault with using waste vegetable oil as bio-diesel.


The team led by Princeton’s Timothy Searchinger noted one possible exceptionsugar cane grown in Brazilwhich takes relatively little energy to grow and is most easily refined into fuel.


Both groups recommend shifting the focus to developing biofuels from agricultural and logging waste products, as is happening in the promising Australian project we covered last week (see “Bio-Fuel Breakthrough Claimed by Australians”).



Sources

  • Searchinger T, Heimlich R, Houghton RA, Dong F, Elobeid A, Fabiosa J, Tokgoz S, Hayes D, Yu T. Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land Use Change. Published online February 7 2008; 10.1126/science.1151861 (Science Express Reports)
  • Fargione J, Hill J, Tilman D, Polasky S, Hawthorne P. Land Clearing and the Biofuel Carbon Debt. Published online February 7 2008; 10.1126/science.1152747 (Science Express Reports)
  • Princeton University. New study by STEP researcher Searchinger: biofuels may increase greenhouse gas emissions. Accessed online February 10, 2008 at http://wws.princeton.edu/coverstories/searchinger_article/index.xml
  • German Marshall Fund of the United States. Converting forest and grassland to cropland adds previously unforeseen greenhouse gas emissions to the cost of biofuels, new study says. Accessed online February 10, 2008 at http://www.gmfus.org/press/article.cfm?id=132&parent_type=R.

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