Thinking it through: Scientists call for policy to guide biofuels industry toward sustainability

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"The identification of unintended consequences early in the development of alternative fuel strategies will help to avoid costly mistakes and regrets about the effects on the environment," the authors write. Melillo is co-director of the Marine Biological Laboratory's (MBL) Ecosystems Center, and the other authors are environmental scientists, agronomists, and economists from numerous organizations in the United States and Brazil.

The biofuels industry in the United States has significant momentum, but no environmental performance standards are currently in place. In May, the 2008 Farm Bill was passed, which provides subsidies for growers of biofuels crops and for refiners who convert those crops to ethanol. Also, the U.S. Legislature approved a mandate in 2007 for the production of 16 billion gallons of cellulosic ethanol per year by 2022.

"We have a lot of information that can help policy makers think through the long-term consequences of this kind of mandate," Melillo says. "We can help society avoid or at least reduce some of the negative consequences of the expansion of biofuels programs in the United States and around the world. Science can help all of us use renewable resources, such as biofuels, in a sustainable way."

The Farm Bill specifically subsidizes the production of "advanced" or cellulosic biofuels, which are biofuels, such as ethanol, derived by processing the complex organic molecule, cellulose, which makes up a large amount of most plant materials. In the United States today, we produce most of the biofuel ethanol from the fermentation of sugars and starches from corn kernels. Melillo says, "The new Farm Bill promotes the use of the inedible parts of corn, the cellulose-rich stalks and stover, for biofuels. Further down the line, it is expected that perennial, cellulose-rich plants such as switchgrass, miscanthus (a tropical grass), willow, and poplar will be grown specifically for biofuels production."

"Many of the problems associated with biofuels are more generally problems with agriculture," Melillo says. Current grain-based biofuel cropping systems are known to cause environmental harm, including soil erosion and depletion, nitrogen fertilizer pollution, and a decline in biodiversity leading to pest management issues. The switch to perennial biofuels crops, such as grasses, shrubs and trees, can mitigate some of these problems and prevent competition with food production. Still, if these crops are sited on marginal lands rather than on cropland, the land could require sizeable inputs of water, nutrients, and energy to become productive.

"If it takes a lot of inputs and if negative environmental consequences persist, then you clearly diminish the benefit you would derive from biofuels production," Melillo says. All the tradeoffs between alternative biofuels strategies need to be carefully considered, the authors write.

One motive for biofuels production is to increase domestic energy security by reducing reliance on imported oil. In addition, introducing biofuels into the nation's energy portfolio promises to reduce the amount of CO2 and greenhouse gases going into the atmosphere by fossil-fuel burning. But this, too, must be carefully thought through by the use of scientific analyses, Melillo says. In some parts of the world, the decision is being made to burn forests to clear land for biofuels crops, which releases a large amount of CO2 into the atmosphere just to set the cropland up. "You have to go into that game knowing you are creating a carbon debt; knowing you are borrowing a lot of carbon from nature where it is stored in plants, and putting it into the atmosphere. In this case, you must recognize that you will not invoke carbon savings from biofuels for a while, perhaps a very long while," Melillo says. "You don't want this to be an unrecognized, unintended consequence."

"Sustainable biofuel production systems could play a highly positive role in mitigating climate change, enhancing environmental quality, and strengthening the global economy," the authors conclude, "but it will take sound, science-based policy and additional research effort to make this so."

Marine Biological Laboratory