It’s Carbon Payback Time

A recent study from researchers at the University of Wisconsin takes another look at the “carbon debt” models proposed by Searchinger and Fargione in ScienceXpress earlier this year. Searchinger and Fargione argued that biofuel development in the United States and Europe would lead to the destruction of rainforests and grassland in Brazil and other tropical climates, which would of course release massive amounts of carbon into the atmosphere (See earlier posting).

The new study takes into account some factors that other researchers criticized Fargione and Searchinger for ignoring. Bringing crop yields in the developing world up to the production level in the United States would increase biofuels’ carbon recycling benefits by up to 50 percent, according to the study authors. Further, if biofuels displace future production of oil from tar sands, their climate benefit will increase by another 25 percent. The researchers conclude that “future carbon payback times could be substantially shorter with increases in crop yields, changing petroleum sources and improved biofuel technology.”

Biofuels could have immediate benefits, the study authors conclude, if they are grown on degraded farm land. As another recent study from Stanford University shows, there are nearly 1 billion acres of abandoned farm land around the world. Some of this former agricultural land was once pasture grazed by cattle, and some was cropland that was abandoned for greener fields or because of changing needs. The study’s principle author calculates there is enough land in the United States to supply 9 percent of U.S. transportation energy, using current crop yield data.


4 Responses

  1. I don’t know how you can read the first study and conclude that it is favorable to biofuels development. Sure, with radical change and advanced technology, things could be better, but the article concludes that we should considered *current* biofuels practices and harms when making immediate policy changes. This is from the conclusion of the article:

    Moreover, these changes in technology require further research, development, and investment before they will impact global biofuels supplies (IEA 2006). As a result, only the carbon payback times under current conditions should be considered for immediate policy decisions. Navigating the waters between current decisions and future technologies is a major challenge: how long will we use current agricultural systems and biofuel technologies until next-generation methods are available, and how can we avoid serious environmental damages in the meantime? How do we move through these technical, policy and market transitions, striking a balance between supporting developing markets and technologies, while minimizing the unintended environmental and social costs? In the meantime, rising biofuel demand may unintentionally increase greenhouse gas emissions to the atmosphere through increased pressure on carbon-rich tropical ecosystems, particularly over the next decade while we rely on current-generation technology. These increased emissions could be particularly problematic if they push our changing climate system closer to dangerous tipping points.

    Indeed, as we look to the future—with growing population, increasing dietary affluence, and increasing energy demands—agricultural expansion in the tropics to produce food, feed and fuel appears inevitable. Global demand for feed and food is expected to nearly double in the next half-century, and demand for transport fuels will increase even faster (IEA 2006)—with both factors adding pressure on tropical forests (Searchinger et al 2008, Nepstad et al 2006, 2008). Thus, it is critical that we move quickly to provide policy and economic incentives to protect tropical forests (Santilli et al 2005, Gullison et al 2007), while other potentially carbon beneficial pathways for biofuel expansion are explored.

  2. Thank you for the thoughtful comment. Much appreciated.
    I would not claim that either study discussed here is pro- or anti-biofuel. They are both serious and much-needed attempts to refine the models proposed by Fargione and Searchinger earlier this year and contributions to the growing literature on calculating the greenhouse gas emissions attributable to biofuels, something that is required under the Renewable Fuel Standard. To meet the RFS, biofuels must reduce greenhouse gases by between 20 and 60 percent, and the industry needs a standard model for making that calculation. Whether we can accurately calculate the pressure put on rainforests by biofuel production in the U.S. is still an open question.

  3. The only way I can get on board with Bio Fuels is if we don’t ship them more then a 100 miles. Kinda defeats the purpose other wise. We’ll call it “Macro Fuel”

  4. […] Comments How to Measure Land … on Biofuels and Carbon DebtRay The Money Man on It’s Carbon Payback Tim…hungrybritain on Purdue University Weighs In on…Karim Virani on Purdue University Weighs In […]

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