Study critiques corn-for-ethanol's carbon footprint

Mar 02, 2009

To avoid creating greenhouse gases, it makes more sense using today's technology to leave land unfarmed in conservation reserves than to plow it up for corn to make biofuel, according to a comprehensive Duke University-led study.

"Converting set-asides to corn-ethanol production is an inefficient and expensive greenhouse gas mitigation policy that should not be encouraged until ethanol-production technologies improve," the study's authors reported in the March edition of the research journal Ecological Applications.

Nevertheless, farmers and producers are already receiving federal subsidies to grow more corn for ethanol under the Energy Independence and Security Act of 2007.

"One of our take-home messages is that conservation programs are currently a cheaper and more efficient greenhouse gas policy for taxpayers than corn-ethanol production," said biologist Robert Jackson, the Nicholas Professor of Global Environmental Change at Duke's Nicholas School of the Environment, who led the study.

Making ethanol from corn reduces atmospheric releases of the greenhouse gas carbon dioxide because the CO2 emitted when the ethanol burns is "canceled out" by the carbon dioxide taken in by the next crop of growing plants, which use it in photosynthesis. That means equivalent amounts of carbon dioxide are removed from the atmosphere and "fixed" into plant tissues.

But the study notes that some CO2 not counterbalanced by plant carbon uptake gets released when corn is grown and processed for ethanol. Furthermore, ethanol contains only about 70 percent of gasoline's energy.

"So we actually reduce greenhouse gas emissions only 20 percent when we substitute one liter of ethanol for one liter of gasoline," said Gervasio Piñeiro, the study's first author, who is a Buenos Aires, Argentina-based scientist and postdoctoral research associate in Jackson's Duke laboratory.

Also, by the researchers' accounting, the carbon benefits of using ethanol only begin to show up years after corn growing begins. "Depending on prior land use" they wrote in their report, "our analysis shows that carbon releases from the soil after planting corn for ethanol may in some cases completely offset carbon gains attributed to biofuel generation for at least 50 years."

The report said that "cellulosic" species -- such as switchgrass -- are a better option for curbing emissions than corn because they don't require annual replowing and planting. In contrast, a single planting of cellulosic species will continue growing and producing for years while trapping more carbon in the soil.

"Until cellulosic ethanol production is feasible, or corn-ethanol technology improves, corn-ethanol subsidies are a poor investment economically and environmentally," Jackson added.

However, the report noted that a cost-effective technology to convert cellulosics to ethanol may be years away. So the Duke team contrasted today's production practices for corn-based ethanol with what will be possible after the year 2023 for cellulosic-based ethanol.

By analyzing 142 different soil studies, the researchers found that conventional corn farming can remove 30 to 50 percent of the carbon stored in the soil. In contrast, cellulosic ethanol production entails mowing plants as they grow -- often on land that is already in conservation reserve. That, their analysis found, can ultimately increase soil carbon levels between 30 to 50 percent instead of reducing them.

"It's like hay baling," Piñeiro said. "You plant it once and it stays there for 20 years. And it takes much less energy and carbon dioxide emissions to produce that than to produce corn."

As part of its analysis, the Duke team calculated how corn-for-ethanol and cellulosic-for-ethanol production -- both now and in the future -- would compare with agricultural set-asides. Those comparisons were expressed in economic terms with a standard financial accounting tool called "net present value."

For now, setting aside acreage and letting it return to native vegetation was rated the best way to reduce greenhouse gas emissions, outweighing the results of corn-ethanol production over the first 48 years. However, "once commercially available, cellulosic ethanol produced in set-aside grasslands should provide the most efficient tool for greenhouse gas reduction of any scenario we examined," the report added.

The worst strategy for reducing carbon dioxide emissions is to plant corn-for-ethanol on land that was previously designated as set aside -- a practice included in current federal efforts to ramp up biofuel production, the study found. "You will lose a lot of soil carbon, which will escape into the atmosphere as CO2," said Piñeiro.

Source: Duke University

Explore further: Predicting bioavailable cadmium levels in soils

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

Predicting bioavailable cadmium levels in soils

16 hours ago

New Zealand's pastoral landscapes are some of the loveliest in the world, but they also contain a hidden threat. Many of the country's pasture soils have become enriched in cadmium. Grasses take up this toxic heavy metal, ...

Oil drilling possible 'trigger' for deadly Italy quakes

20 hours ago

Italy's Emilia-Romagna region on Tuesday suspended new drilling as it published a report that warned that hydrocarbon exploitation may have acted as a "trigger" in twin earthquakes that killed 26 people in ...

Snow is largely a no-show for Iditarod Trail Sled Dog Race

20 hours ago

On March 1, 65 mushers and their teams of dogs left Anchorage, Alaska, on a quest to win the Iditarod—a race covering 1,000 miles of mountain ranges, frozen rivers, dense forest, tundra and coastline. According ...

UN weather agency warns of 'El Nino' this year

20 hours ago

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

Study shows less snowpack will harm ecosystem

21 hours ago

(Phys.org) —A new study by CAS Professor of Biology Pamela Templer shows that milder winters can have a negative impact both on trees and on the water quality of nearby aquatic ecosystems, far into the warm growing season.

User comments : 8

Adjust slider to filter visible comments by rank

Display comments: newest first

Modernmystic
3.3 / 5 (4) Mar 02, 2009
Double your food prices AND waste a few billion in government research money on a useless technology!

Its one heck of a twofer!
Sean_W
4.3 / 5 (3) Mar 02, 2009
Ethanol is not the future of transportation and corn ethanol subsidies are wasteful and distort the market but ethanol is a valuable chemical feed stock and solvent. Not all reductions in petroleum use comes at the engine level. And at a time when urbanization and agricultural productivity gains are turning farmland into jungle, the price of food has far more to do with energy/transportation costs than competition with any biofuel.
GrayMouser
2.7 / 5 (3) Mar 02, 2009
Interesting that we need to proactively react against CO2 without any "reasonable" technology but we should hold off on one of those technologies until it becomes more mature. Kind of a double standard?
lengould100
4 / 5 (1) Mar 03, 2009
No double standard, GrayMouser. The idea is to do everything we know how to do now to reduce GHG emissions. At now, that does NOT include converting corn into ethanol. Ethanol from biomass must wait until cellulosic technology is available.

I don't see your point.
Icester
5 / 5 (2) Mar 03, 2009
Finally... a study that supports what I've been telling people for the last several years.

Hmmm... I wonder if Gore (Mr. Global Warming) will propose a tax on ethanol (at least until cellulosic ethanol)? If not, wouldn't that be a double standard?
PaulLove
1.7 / 5 (3) Mar 03, 2009
The funding you will note comes from the energy independence and security act. To that end ethanol is successful, it is a domestic source of fuel thus reducing the dependence on foreign energy sources not perhaps as much as converting to a pure hydrogen economy but as start its something.

For the carbon footprint the study suggests that it may take as many as 50 years to offset the carbon release of planting corn for those who complain care to make a guess at when you recover the carbon footprint of burning fossil fuels that have been sequestered for MILLIONS of years? If you wait 10-15 year to perfect the technology do you suppose that in 10 or 15 years there will be an even more perfect technology? Will you then council we wait an additional 10-15 years?
Arkaleus
4.3 / 5 (3) Mar 03, 2009
My simple preposition is this:

Prove your basic assumptions before you start building complex relationships onto them. Until the alarmists can account for the failure of their climate models for the past ten years, their "solutions" are not justified.

They claim climate is driven by CO2, and that the small percentage of total CO2 output into the atmosphere per year that human activities cause is the cause of climate change. Yet the climate has not warmed as they have predicted, and none of their models has passed even the level of scrutiny required of undergraduate students attempting the same research.

But we know the truth - AGW "solutions" are driven by the need to create a new mode of human control, enabling a frustrated class of professionals to access the powers of government and taxation. If they are successful in establishing climate change as the justification for their social policies, then they achieve a new paradigm of power that does not regard politics and promulgates itself like a state religion - forcing all to give obedience and tribute to itself, while remaining aloof from review by the body politic. I can see the obvious temptation of these intelligent men, but they underestimate the intelligence of the rest of us. Their entire scheme requires the people to lack basic reasoning ability and assumes they accept what they are told by media because they refuse/lack the abilty to critically examine the errors of ambition and deception.

By and large, the people of the United States reject the fabrications of climate quackery, and see through its veil of benevolence and into the face of its ambition.
mmstick
1 / 5 (1) Mar 06, 2009
This is all crap. Bring out the thermal energy and planetary grid already....

More news stories

Warm US West, cold East: A 4,000-year pattern

Last winter's curvy jet stream pattern brought mild temperatures to western North America and harsh cold to the East. A University of Utah-led study shows that pattern became more pronounced 4,000 years ago, ...

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

First direct observations of excitons in motion achieved

A quasiparticle called an exciton—responsible for the transfer of energy within devices such as solar cells, LEDs, and semiconductor circuits—has been understood theoretically for decades. But exciton movement within ...

Patent talk: Google sharpens contact lens vision

(Phys.org) —A report from Patent Bolt brings us one step closer to what Google may have in mind in developing smart contact lenses. According to the discussion Google is interested in the concept of contact ...

Tech giants look to skies to spread Internet

The shortest path to the Internet for some remote corners of the world may be through the skies. That is the message from US tech giants seeking to spread the online gospel to hard-to-reach regions.

Wireless industry makes anti-theft commitment

A trade group for wireless providers said Tuesday that the biggest mobile device manufacturers and carriers will soon put anti-theft tools on the gadgets to try to deter rampant smartphone theft.