March 5, 2008

Want to Increase Your Greenhouse Gas Emissions? Use Biofuels!

Filed under: Agriculture, Climate Politics

In almost every essay we feature at World Climate Report, our focus is on climatic phenomena and the general disagreement between observations and what numerical models of climate tell us should be happening given the ongoing buildup of greenhouse gases. We draw heavily from the professional scientific peer-reviewed literature, and our journals of choice range from highly specialized journals in the climate community to far more generalized, but very highly respected journals such as Science and Nature.

A recent article in Science really caught our eye with the title “Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use Change.” This article is not going to be well received by a lot of people given 1000s of websites telling us to switch to biofuels in an effort to reduce greenhouse gas emissions – it looks like those darn “unintentional consequences” are about to bite another great-sounding idea squarely in the butt.

This sure to be controversial piece was written by Timothy Searchinger of the prestigious Woodrow Wilson School at Princeton University and his daring eight associates from major institutions ranging from Woods Hole Research Center to the Center for Agricultural and Rural Development at Iowa State University. Before you run off and believe this must have been funded by some biofuel competitor, the authors note that “This material is based in part upon work supported by NASA under grant number NNX06AF15G issued through the Terrestrial Ecology Program and by the William and Flora Hewlett Foundation.”

They begin their article stating “Most life-cycle studies have found that replacing gasoline with ethanol modestly reduces greenhouse gases (GHGs) if made from corn and substantially if made from cellulose or sugarcane. These studies compare emissions from the separate steps of growing or mining the feedstocks (such as corn or crude oil), refining them into fuel, and burning the fuel in the vehicle. In these stages alone, corn and cellulosic ethanol emissions exceed or match those from fossil fuels and therefore produce no greenhouse benefits. But because growing biofuel feedstocks removes carbon dioxide from the atmosphere, biofuels can in theory reduce GHGs relative to fossil fuels.” This is the story we learn on all those websites trumpeting the benefits of biofuels – it is all made to look so easy, everyone wins, and biofuels basically buy us time until the next generation of sustainable energy sources are discovered and implemented on a global scale.

Searchinger et al. bring up a little problem that is beginning to rear its ugly head as they write “To produce biofuels, farmers can directly plow up more forest or grassland, which releases to the atmosphere much of the carbon previously stored in plants and soils through decomposition or fire.” Furthermore we learn “As land generates more ethanol over years, the reduced emissions from its use will eventually offset the carbon debt from land-use change, which mostly occurs quickly and is limited in our analysis to emissions within 30 years. We calculated that GHG savings from corn ethanol would equalize and therefore “pay back” carbon emissions from land-use change in 167 years, meaning GHGs increase until the end of that period. Over a 30-year period, counting land-use change, GHG emissions from corn ethanol nearly double those from gasoline for each km driven.”

Now isn’t that great news, switch to biofuels to presumably reduce your greenhouse gas emission and in reality, you double your greenhouse gas emission! Drive around for 167 years and you will finally begin to realize some savings to your greenhouse gas emission – makes sense, right?

From all the biofuels websites, you will discover a crowd that is in love with switchgrass or sugarcane as sources for ethanol production. Well, Searchinger et al. analyzed the situation there as well and concluded “But if American corn fields of average yield were converted to switchgrass for ethanol, replacing that corn would still trigger emissions from land-use change that would take 52 years to pay back and increase emissions over 30 years by 50%”. For sugarcane fans, we learn “Ethanol from Brazilian sugarcane, based on estimated GHG reductions of 86% excluding land-use changes, could pay back the up-front carbon emissions in 4 years if sugarcane only converts tropical grazing land. However, if displaced ranchers convert rainforest to grazing land, the payback period could rise to 45 years”. Finally, they warn “Higher prices triggered by biofuels will accelerate forest and grassland conversion there even if surplus croplands exist elsewhere.” Bye-bye rainforest, all in the name of biofuels which we can burn and increase our greenhouse gas emission – makes good sense to us??

The authors conclude “Use of good cropland to expand biofuels will probably exacerbate global warming in a manner similar to directly converting forest and grasslands. As a corollary, when farmers use today’s good cropland to produce food, they help to avert GHGs from land-use change.” We can only imagine the email Timothy Searchinger has been receiving following the publication of this article – we feel his pain.

By the way, we are not against biofuels. The Searchinger et al. team states “This study highlights the value of biofuels from waste products because they can avoid land-use change and its emissions. To avoid land-use change altogether, biofuels must use carbon that would reenter the atmosphere without doing useful work that needs to be replaced, for example, municipal waste, crop waste, and fall grass harvests from reserve lands. Algae grown in the desert or feedstocks produced on lands that generate little carbon today might also keep land-use change emissions low, but the ability to produce biofuel feedstocks abundantly on unproductive lands remains questionable.”

The biofuels advocates probably realize Searchinger et al. are right, but as with so many other components of the greenhouse debate, the facts will be inconvenient, and biofuels will be promoted as a way to reduce greenhouse gas emissions. Go figure?


Searchinger, T.R. Heimlich, R.A. Houghton, F. Dong, A. Elobeid, J. Fabiosa, S. Tokgoz, D. Hayes, T.-H. Yu. 2008. Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use Change. Science, 319, 1238-1240.

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