|
|
||||||||||||||||||||||||||||||||||
 |
||||||||||
|
 |
|
|
|
|
|||||
|
||||||||||
|
|
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 — 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: Why do many people think that biofuels will actually decrease greenhouse gas emissions?
Joe Fargione: Previous conclusions that biofuels reduce greenhouse gases were based on incomplete analyses. They did not include the effect that biofuels 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.
Further, the two main reasons for the recent increase of corn ethanol in the United States are rural economic development and energy security. Reducing greenhouse gases was a distant third reason. The results of our study eliminate climate change as a reason for pursuing corn ethanol, but it will still be pursued for the first two reasons.
Nature.org: But won't biofuels contribute to energy security?
Joe Fargione: Unfortunately, not much. Congress recently 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 cause clearing of natural ecosystems 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. So biofuels either directly or indirectly cause land clearing, which 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: The most significant finding from of our research is that our current biofuels are not a viable strategy for reducing climate change. From a climate change perspective, current biofuels are worse than fossil fuels.
However, that does not mean we should just stick with fossil fuels. There is no silver bullet that can stop climate change. We will need many strategies to address this issue — all pursued simultaneously.
We will 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. And we'll need electric or fuel cell cars, because electricity and hydrogen are easier to produce renewably than are liquid transportation fuels.
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.org: Since the biofuel carbon debt is much higher in tropical areas, does it make sense to increase biofuel production in the United States and export those fuels to other countries?
Joe Fargione: No. Increased demand for ethanol corn crops in the United States is contributing to conversion of the Brazilian Amazon and Cerrado.
American farmers traditionally rotated corn crops with soybeans. But now they are planting corn every year to meet the ethanol demand. Instead, Brazilian farmers are planting more of the world’s soybeans — and they’re contributing to deforestation in the Amazon to do it.
And if you're trying to maximize the amount energy gained from land, wind and solar can give you greater energy per acre. Of these three renewable energy sources, biofuels are the least efficient way to use land to produce energy — unless you put windmills above your biofuel crops.
Finally, transporting biofuels long distances is relatively inefficient because biofuels are bulkier than fossil fuels — they contain less energy per gallon. The most efficient use of biofuels will be to produce them in ways that does not require the conversion of natural ecosystems, and to use them close to home.
Nature.org: So is there any place for biofuels in reducing greenhouse gas emissions and slowing climate change?
Joe Fargione: There is a role for biofuels. Although there is no silver bullet to solve climate change, there are many silver BBs.
Biofuels can be a silver BB if produced without requiring additional land to be converted from native habitats to agriculture. For example, biofuels can be made from waste from agriculture and forests, and from native grasses and woody biomass grown on marginal lands unsuitable for crop production.
We not only have to consider how we produce biomass, but how we convert it to energy. Producing liquid transportation fuels may not be the most efficient way to use the energy contained in biomass.
Multiple technologies currently exist that can economically convert biomass for heat, cooling and electricity. To make the best use of biomass from a climate change standpoint, we should consider these uses, not just producing liquid transportation fuel.
Nature picture credits (top to bottom, left to right): Photo © Boyd Schulz (sodbusting); Photo © Photographer/Org (Joe Fargione); Photo © Marcel Silvius (palm oil seedling).
