Biofuels could increase greenhouse gases: US studies

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.

US experts warn that rules governing biofuel production encourage deforestation and mean the technology is therefore a "false" method of reducing 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. "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.

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."

A global push toward production of biofuels, advocated by many as a measure to curb greenhouse gas emissions, could have exactly the opposite effect unless adequate controls are put in place, a new study has found. Because forests, which remove carbon dioxide from the atmosphere, could end up being cut down to create new cropland as a result of intensive agriculture for fuels, a gallon of biofuel could ironically end up being responsible for twice as much greenhouse gas emission as a gallon of gasoline.

This indirect impact from biofuels production is ‘an inescapable effect’ unless regulations control it, but it cannot directly be measured, says John Reilly, associate director of the MIT Joint Program on the Science and Policy of Global Change. Reilly, along with five other MIT researchers, is a co-author of the new study, being published Oct. 23 in Science. The lead author is Jerry Melillo of the Marine Biological Laboratory in Woods Hole, Mass.

The study found that a massive campaign to substitute biofuels for petroleum could result in a net doubling of the amount of land devoted to agriculture worldwide – and that, perhaps surprisingly, there is enough land available to sustain that. But this change in land use, unless coupled to regulations that either specifically protect forestland, or that tax the destruction of forest sufficiently to render that uneconomic, would lead to a net increase in carbon emissions. In addition, the increase in intensive agriculture would require an enormous addition of nitrogen fertilizers to the soil, producing emissions of nitrous oxide, a much more potent greenhouse gas than carbon dioxide.

Together, these two effects could double the overall emissions attributable to land use. However, with proper controls in place, the use of biofuels instead of petroleum could reduce carbon emission by almost four-fifths, Reilly says.

The effects are often indirect and hard to measure, because typically the growing of crops for biofuels – whether traditional food crops such as corn and soy, or new cellulosic crops intended specifically for fuel production – may not be on forestland freshly cleared for that purpose, but on existing agricultural land. But, because of resulting pressures on food supplies and prices, the result may be that forests, perhaps in an entirely different region, are cleared to grow food crops displaced by the fuel production.

Although such indirect effects can’t be directly measured, ‘you need statistical techniques to estimate the land-use change and other factors,’ Reilly says. And that is what the new study attempted to do.

Currently, in many parts of the world there is little protection of large natural forests, and that which exists is often ineffective. Absent effective protection, if an international push toward biofuels production were put in place now, ‘you would probably get this increase in deforestation,’ Reilly says, and the net result could end up being an increase in net greenhouse gas emissions. That increase, for each gallon of biofuel produced, could be ‘two to three times worse than a gallon of gasoline,’ he says. ‘It’s a hugely negative effect.’

Still, the study’s findings don’t necessarily mean that increased biofuel production would be a bad idea, only that it needs to be done in the right way. ‘In order to make this efficient, we need to control deforestation,’ Reilly says. But with sufficient regulations to control the changes in land use and to limit the use of nitrogen fertilizers, he says, ‘it would not have these negative effects, and might have positive effects.’

As the world prepares to negotiate new agreements to control global warming in Copenhagen later this year, Reilly says, it’s important that there be ‘an awareness that this is an issue to look at. It’s not clear that there’s a full awareness of how crucial this is.’ It will be essential to figure out how to treat biofuels correctly in any proposed cap-and-trade system, he says.

Indirect Emissions from Biofuels: How Important?

A global biofuels program will lead to intense pressures on land supply and can increase greenhouse gas emissions from land-use changes. Using linked economic and terrestrial biogeochemistry models, we examine direct and indirect effects of possible land-use changes from an expanded global cellulosic bioenergy program on greenhouse gas emissions over the 21st century. Our model predicts that indirect land use will be responsible for substantially more carbon loss (up to twice as much) than direct land use; however, because of predicted increases in fertilizer use, nitrous oxide emissions will be more important than carbon losses themselves in terms of warming potential. A global greenhouse gas emissions policy that protects forests and encourages best practices for nitrogen fertilizer use can dramatically reduce emissions associated with biofuels production.