As scientists take a close look at the switch from petroleum-based fuels to biofuels, it appears that the reduction of greenhouse gas (GHG) emissions associated with many types of biofuels has been vastly overestimated, according to the Wildlife Management Institute. GHG emissions are primary drivers of global warming.

The initial studies projected an average reduction of approximately 20 percent in GHG emissions as a result of the use of biofuels. However, those estimates did not take into account the release of gases as a result of land-use changes. In recent modeling efforts, in which researchers factored in the carbon costs of land-use changes, GHG emissions are projected to be substantially higher.?

Carbon costs are the carbon storage and sequestration sacrificed by converting nonfarmed lands to production of crops along with carbon previously stored in plants on nonfarmed lands and lost into the atmosphere when nonfarmed lands are cleared to grow crops.

The new models predict that former croplands retired to perennial grasslands, such as with the Conservation Reserve Program, would require up to 48 years to balance the initial "carbon debt" generated by converting a 15-year-old grassland field to corn production for biofuel. Similar analyses for biofuel crops suited to other parts of the world?replacing tropical rain forest with sugar cane production, for example?produced estimates that ran into hundreds of years to balance the carbon debt associated with these kinds of land-use changes.

At a time when biofuel production is being ramped up to augment or replace fossil fuel consumption, the worldwide food demand is increasing. These concurrent factors are serving to drive up the value of crops, which, in turn, makes attractive and profitable the conversion of nonfarmed lands to crop production. As crops formerly providing food are increasingly being used for biofuel, there is tremendous pressure to convert nonfarmed lands to crop production for either use.

While the ecological costs associated with production and use of biofuels are higher than initially thought, researchers note that biofuels can be made from some sources that add little to existing GHG emissions. In a recent letter to the President and leaders of Congress, scientists working on this issue indicated: "Some opportunities remain to produce environmentally beneficial biofuels. Sources of feedstock for biofuels that avoid land use change include municipal or industrial waste, and agricultural wastes. . . . Harvesting fall grass from agricultural reserve lands also holds promise. There is also potential to produce biofuels on some degraded lands or to manage them to increase their ability to capture or store carbon. Although the opportunities to use biofuels to effectively replace fossil fuels are more limited than previously believed, they could remain an important element in a comprehensive program of fossil fuel reduction." (pmr)