Biofuel development is going to add a lot more greenhouse gases to the atmosphere than previously estimated, according to a new assessment published today in Science Express.
In theory, fuel produced from sugar beets, corn or other crops should push less carbon dioxide and other greenhouse gases into the atmosphere than do coal and oil — because the carbon that escapes while burning biofuel is balanced by the carbon the plants absorb while growing. However, according to Jerry Mellilo of the Marine Biological Laboratory’s Ecosystems Center and his colleagues, that theory only counts the direct contribution of a fuel crop to atmospheric carbon dioxide.
People don’t stop farming for food when land is diverted to growing plants for fuel. Instead, they’re more likely to cut down a forest, drain a wetland or saturate a plain with fertilizer in order to create more farmland for food. Mellilo and his colleagues developed a model to predict the carbon dioxide emissions from those new farm and pasture lands. And that model predicts that those lands will add twice as much carbon dioxide to the atmosphere as will the fields devoted to biofuels themselves.
Expanded agriculture will also increase emissions of nitrous oxide, another greenhouse chemical, which is, of course, better known as fertilizer. All in all, the study says, biofuels development as presently conceived is likely to worsen global warming, not help prevent it.
Which, by the way, is another illustration of our need to put aside scientific infantilism: The childish demand that science be more sure and certain than it can be. As the report’s authors write, the indirect effects of biofuel programs are a controversial and unsettled topic. What’s the bottom line about them? We don’t know yet, and we ought to admit it.