Tallying Biofuels' Real Environmental Cost

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William Radcliffe / Science Faction / Corbis

The promise of biofuels like ethanol is that they will someday help the world grow its way out of its addiction to oil. Nine billion gallons of corn ethanol were produced in the U.S. in 2008, while countries like Brazil have already widely replaced gasoline with ethanol from sugar cane and countless start-ups are working to bring cellulosic and other second-generation biofuels to market. The reasoning is that if we use greener biofuels in place of gasoline, it will significantly enhance our effort to reduce greenhouse-gas emissions.

But the question is, Are biofuels really green? A pair of new studies in the Oct. 22 issue of Science damningly demonstrate that the answer is no, at least not the way we currently create and use them. In the first study, a team of researchers led by Jerry Melillo of the Marine Biological Laboratory in Woods Hole, Mass., projected the effects of a major biofuel expansion over the coming century and found that it could end up increasing global greenhouse-gas emissions instead of reducing them. In the second paper, another team of researchers led by Tim Searchinger of Princeton University uncovered a potentially damaging flaw in the way carbon emissions from bioenergy are calculated under the Kyoto Protocol and in the carbon cap-and-trade bill currently being debated in Congress. If that error in calculation goes unfixed, a future increase in biofuel use could end up backfiring and derailing efforts to control global warming, according to the paper. "Biofuels can be an important part of the portfolio of climate-change activities," says Steve Hamburg, chief scientist for the Environmental Defense Fund and a corresponding author on the second Science paper. "But we have to make sure we incentivize the right way, or we could end up with perverse outcomes."

The problem is that biofuels are treated as if they were 100% carbon neutral, even though they are clearly not. When ethanol is burned, for instance, it still releases CO2 into the atmosphere. After all, the plants that go to make biofuels are made of carbon, just as oil and other fossil fuels are. Further, the use of biofuels would reduce total greenhouse-gas emissions only if their creation were to increase — or at least not displace — existing plant growth, which naturally takes carbon out of the atmosphere. For example, if the wood chips left over from logging were used to make biofuel, overall greenhouse gas emissions would be reduced, since that wood waste would have decomposed on the forest floor and released as carbon into the atmosphere anyway. By using them for fuel, it not only replaces some fossil fuel but also does not destroy plant life.

But that's rarely how it works in most biofuel production today. Instead, a long-standing forest might be clear cut in Indonesia and replaced with a plantation of palms to make biodiesel. That's where the accounting error crops up: we should assess the carbon lost in deforestation when we measure the greenness of biofuels, but that's not how it works under Kyoto, which simply exempts all CO2 emissions that come from using biofuels. CO2 emissions resulting from deforestation or other changes in the way we use land are not evaluated at all. The result is a huge, if accidental error in the existing global carbon accounting system — and one that now stands to be repeated in the cap-and-trade bill up for debate in Congress. "It's a very, very large loophole," says Searchinger, who had done pioneering work on problems of biofuels. "We're just effectively ignoring what happens on land."

Given how limited the impact of the Kyoto Protocol has been, the effects of that error have been modest so far. But if the U.S. adopts a cap-and-trade system with the same mistake, or if the world agrees to a truly global successor to Kyoto, the blowback could be enormous. As long as biofuels are incorrectly treated as 100% carbon neutral, they'll represent an economical way for companies to offset their greenhouse-gas emissions and comply with a tightening carbon cap. One study estimates that if the world were to meet a 50% "cut" in global greenhouse gases by 2050 under the current calculations, the necessary biofuel-crops expansion would be large enough to displace 59% of the world's natural forest cover — which would release an additional 9 billion tons of CO2 a year. "Carbon capture and storage, solar power, electric batteries — all of these alternatives have serious costs," says Searchinger. "But if you can just use up the world's carbon in forests to meet your cap, that turns out to be pretty cheap."

There are other side effects as well. Melillo's paper points out that if biofuels scale up rapidly, they could end up displacing cropland and pasture, which would impact global food supplies and increase land-based carbon emissions. Melillo found that if biofuels were linked to a global policy to stabilize carbon concentrations in the atmosphere at 550 parts per million — a modest goal — we would need more land for biofuel production by the end of the 21st century than is currently used for all food crops. Worse, all the fertilizer needed to grow those bioenergy crops would increase emissions of nitrous oxide, an extremely potent greenhouse gas, and water supplies would also be stressed. "We have to think about this very carefully," says Melillo. "We need to have a complete analysis about the unintended consequences of biofuels."

The good news is that closing the biofuel loophole isn't that complex. All emissions from biofuels should simply be counted as carbon, and companies or countries that get their biofuels from sources that actually reduce greenhouse gases should get credit for those cuts. But politics will be another matter — the biofuel industry already has a lot of weight, especially in the U.S., where environmentalists need the votes of rural and Midwestern representatives in Congress if they are to have any hope of passing a cap-and-trade bill. Challenging the biofuel loophole could effectively scuttle cap-and-trade in the U.S.

And that may well be a boon. If cap-and-trade were passed with the existing biofuel loophole, it could set up a system that would incentivize the expansion of bioenergy at the expense of the environment and carbon cutting. Certainly the error could be fixed later, after the bill is passed — but by that time the financial interests in favor of biofuels would be even stronger, and would surely resist changes. "If this isn't fixed, you could give companies a very powerful financial incentive to go clear land," says Searchinger, who has briefed members of Congress on his research. "As it stands, forests will be worth more dead than alive." Environmental groups will need to rethink their approach to cap-and-trade — and biofuels as well. It's the very definition of an inconvenient truth.