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A new study from The Nature Conservancy and the University of Minnesota finds that many biofuels — seen by many as a potentially low-carbon energy source — could actually emit more greenhouse gases than the fossil fuels they aim to replace.
According to the study, co-authored by Joe Fargione, a regional scientist for the Conservancy, “converting rainforests, peatlands, savannas, or grasslands to produce biofuels in Brazil, Southeast Asia, and the United States creates a ‘biofuel carbon debt’ by releasing 17 to 420 times more carbon dioxide than the fossil fuels they replace."
Nature.org talked to Fargione about this first-of-its-kind study and its implications for the future of biofuels and climate change.
Nature.org: Previous research found that biofuels decrease greenhouse gas emissions. How does your research differ from these previous studies?
Joe Fargione: Previous conclusions that biofuels reduce greenhouse gases were based on incomplete analyses. They did not include the effect that biofuels can have on the conversion of natural ecosystems to crops. Most people don’t realize that globally there is almost three times as much carbon in the plants and soils as there is in the air. Our natural ecosystems provide an incredibly valuable service of carbon storage and climate stabilization if they are left intact.
Nature.org: But won't biofuels contribute to energy security?
Joe Fargione: Unfortunately, not as much as most people think. In 2007, congress passed a 36-billion-gallon biofuel mandate, but that will offset only 14 percent of projected gasoline usage by the year 2022 and would require about 60 million acres. After accounting for the energy needed to produce the ethanol, the true offset would only be 8-11 percent.
Nature.org: Define "biofuel carbon debt" for us. And why is it important for understanding the true impact of biofuels on climate change?
Joe Fargione: All the biofuels we use now require additional land for agriculture. Adding energy production to our current and growing demand for food production inevitably requires more land to be converted to agriculture, whether or not the biofuel is grown directly on that land. Some of this land comes from natural ecosystems, and the conversion of these natural ecosystems to cropland releases carbon to the atmosphere and contributes to global warming. This is the biofuel carbon debt.
Now, making and using biofuels adds less carbon to the atmosphere than does making and using fossil fuels — if you ignore the effects of land clearing. But how does this compare to the carbon debt from land clearing? How many years would you have to use biofuels for the amount of carbon saved to exceed the amount of carbon released by land clearing?
Let’s say you drain and clear an Indonesian peat bog and replant it with palm oil for biofuel. Over 50 years, the carbon released by the decomposing peat would end up being 420 times greater than the carbon saved by using one year of palm biodiesel. This means that it would take 420 years of using that biofuel to “pay off the debt” of carbon that is released by draining and clearing peatland.
Nature.org: So, given this "carbon debt" that is created, would it be better — from a climate change perspective — for us to just stick with fossil fuels and concentrate on conservation methods like increasing mass transit use and overall efficiency?
Joe Fargione: There are several alternatives to current biofuels that would help us to reduce our dependence on fossil fuels and reduce carbon emissions. We can make biofuels from sources that don’t require additional land, such as agricultural wastes, cover crops, municipal waste, animal waste, forestry waste, forest thinning for fire risk reduction, and storm and pest damaged trees. Algae production offers the potential for dramatic increases in yields and can more easily avoid conflicts with land use. We can also make biofuels in ways that create habitat, rather than contribute to its conversion, for example by using biomass from diverse prairie.
We will also need greater efficiency in our buildings and transportation. We'll need protection of the carbon stored in natural ecosystems. We'll need renewable energy — including wind and solar, carbon capture and storage. Wind uses about 1/5 the amount of land to produce the equivalent energy as biofuels, and solar uses about 1/25 the amount of land to produce the same energy as biofuels. if you're trying to maximize the amount energy gained from land, wind and solar can give you greater energy per acre. Biofuels require the most land of any form of energy production. So we'll need electric or fuel cell cars, because electricity and hydrogen are easier to produce renewably than are liquid transportation fuels. Even if you are using biomass to power cars, you can drive about twice as far if you convert that biomass to electricity to power an electric car as you can if you convert to biofuels to power a conventional car.
Nature.org: The United States and the rest of the world seem to be moving toward biofuels as at least part of a solution to reducing dependence on fossil fuels. What sort of policies should governments enact to ensure that biofuels don't exacerbate the climate change problem?
Joe Fargione: Any strategy used to reduce carbon emissions must take land use change into account, or it won’t work.
This maxim holds regardless of the policy tool used, be it a carbon tax, carbon cap and trade, or low carbon fuel standards. Without accounting for land-use change, policies penalizing fossil fuel are likely to have the perverse effect of promoting biofuels that lead to an increase in carbon emissions.
Nature picture credits (top to bottom, left to right): Photo © Boyd Schulz (sodbusting); Photo © Photographer/Org (Joe Fargione); Photo © Marcel Silvius (palm oil seedling).
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