Biofuels hold promise for reducing the world’s consumption of unsustainable fossil fuels. But like any new technology, they come with their own host of issues and problems. One such problem is the so-called “indirect” effect of biofuels on the landscape and the atmosphere. For example, when farmlands are converted to biofuel crops, the food formerly grown on those lands needs to be grown somewhere else. This could mean clearing of more forests to make room for more agricultural land, releasing carbon into the atmosphere.
A paper out in the Dec. 4 issue of Science investigates just these indirect effects. Jerry Melillo of the Marine Biological Laboratory at Woods Hole and his coauthors devised an economic and biogeochemical model to estimate the indirect costs of potential global cellulosic biofuel production on the environment and how they compare to the new technology’s direct effects.
Unsurprisingly, the authors found that indirect effects are large. Surprisingly, however, they found that indirect environmental effects of biofuel production account for up to twice the amount of terrestrial carbon loss as the direct environmental effects. In addition, use of larger net amounts of fertilizer across farm and biofuel lands will contribute to the release of nitrous oxide to the atmosphere; nitrous oxide is about 300 times more potent as a greenhouse gas than carbon dioxide.
The authors acknowledge that the methods to assess indirect effects of biofuel production on the environment are controversial. Some analyses include only part of the picture, while others ignore indirect effects completely. Even if the measurements are crude, they assert, their study shows their paramount importance. As they write:
There are a variety of concerns about the practicality of including land-use change emissions in a system designed to reduce emissions from fossil fuels, and that may explain why there are no concrete proposals in major countries to do so. In this situation, fossil energy control programs (LCFS or carbon taxes) must determine how to treat the direct and indirect GHG emissions associated with the carbon intensity of biofuels.
Melillo, J., Reilly, J., Kicklighter, D., Gurgel, A., Cronin, T., Paltsev, S., Felzer, B., Wang, X., Sokolov, A., & Schlosser, C. (2009). Indirect Emissions from Biofuels: How Important? Science, 326 (5958), 1397-1399 DOI: 10.1126/science.1180251