Corn Ethanol or Conservation? What Do You Think?

by Bill Chameides | March 16th, 2009
posted by Erica Rowell (Editor)

Permalink | 6 comments

U.S. corn ethanol production has been on the rise. That’s good for our country’s carbon footprint, right? A new study suggests not.

The federal government has had a love affair with corn ethanol. In the Energy Independence and Security Act of 2007, Congress increased the mandate for renewable biofuels production in the United States by a factor of almost 7 — from 5.4 billion gallons in 2008 to 36 billion gallons by 2022 — the vast majority of which would have to come at least in the near term from corn ethanol. Even President Obama has gotten into the act, proposing that the amount of ethanol in gasoline be increased from 10 percent to 12 or 13 percent.

Good for the climate, right? After all, the carbon in a biofuel comes from plant materials, which got their carbon by taking carbon dioxide (CO2) from the atmosphere during photosynthesis. So burning fuel just sends that same carbon back into the atmosphere — no net change in carbon dioxide and no climate impact. Right? Wrong.

No Climate Benefit from Corn Ethanol at Present

In principle that’s the way it works, but in practice it’s more complicated.

Growing crops requires energy in the form of fossil fuels and requires fertilizers, which also emit greenhouse gases. Those factors reduce the energy and greenhouse benefits of using corn as a feedstock for ethanol.

However, recent studies suggest that corn ethanol production, using modern, energy-efficient practices, has a net energy benefit and an apparent climate benefit — it’s apparent because if you take into account the probable land-use changes that adding new, domestic corn ethanol capacity will require, the climate benefits evaporate.

Problems arise because increasing the country’s production of corn ethanol requires farmers to place more land into corn cultivation. Ultimately, that means that land not in cultivation somewhere must be cultivated to make up the difference. And when you put otherwise fallow land into production, a significant fraction of the carbon stored in its soil is sent into the atmosphere as CO2, one of the most abundant greenhouse gases.

A couple of papers published in Science last year (see here and here) showed that often the new cultivated acreage comes from converting tropical rain forests in Brazil into soybean farms. The result: significant net emissions of greenhouse gas emissions.

Converting Land Set Aside for Conservation Into Ethanol-Producing Lands Is Not a Good Idea

But there is another, less exotic source of new land for cultivation, one closer to home and even more under our control. It comes from land set aside in the federal government’s Conservation Reserve Program (CRP) — a voluntary program that effectively pays farmers to take land out of production. In the CRP, land owners sign a lease for a 10-15 year period to allow specific ranch or farmland to go fallow with grasses and trees. Environmental benefits of the CRP include: improved soil and water quality, more wildlife habitat, and increases in the amount of soil carbon. This last benefit is important, because the more carbon stored in the soil, the less CO2 in the atmosphere.

However, as demand for corn increases, farmers are under increasing pressure to take their land out of the CRP when their leases expire and cultivate them again.

Right now about 33 million acres of land [pdf] are enrolled in the CRP. But that acreage has started to drop off in recent years, and, believe it or not, Congress reduced the cap on CRP lands from 39.2 million acres to 32 million acres in the Farm Bill of 2008.

New Study: Conservation to Corn Is Like Fueling the CO2 Fire

What happens when CRP lands are converted to corn cultivation to produce corn ethanol? My colleague at Duke, Rob Jackson, and his co-authors report in the latest issue of Ecological Applications that at least in terms of greenhouse gases the results are not pretty. Because of the loss of soil carbon, producing corn ethanol on former CRP lands releases almost 40 tons of CO2 per hectare in the first decade. This means that switching just 10 percent of CRP land to corn cultivation would add nearly 50 million more tons of CO2 to the atmosphere in 10 years. That’s about the same amount of emissions as putting an additional 850,000 cars on the roads over the same time period.

Over time, the benefits of displacing gasoline with corn ethanol do begin to pay off. After about 30 years, converting CRP lands to corn ethanol production would break even in terms of greenhouse gas emissions. And after some 50-70 years, the conversion would begin to outdo just leaving the CRP land in place.

A Winner in the Making: Cellulosic Ethanol

The good news is that Jackson and colleagues do find a potential greenhouse-gas winner in the biofuels sweepstakes: cellulosic ethanol. Cellulosic ethanol can be produced from grasses grown with little or no cultivation — thus allowing carbon to build up in the soil at the same time the grasses are harvested for ethanol. (The big assumption here is that since cellulosic ethanol can be grown on degraded rather than prime agricultural lands, it won’t drive the same land-use changes that ultimately make corn-ethanol production a net greenhouse gas loser.)

So here’s the thing. Cellulosic ethanol is on a track to become commercially available in a matter of years. Once it does, it will make corn ethanol yesterday’s news. So why set up policies to force extra production of corn ethanol now and encourage the loss of CRP lands for a questionable, short-term benefit in terms of biofuel availability and a definite step backward in terms of climate mitigation?

Of course, with the collapse of gasoline demand and prices, the federal policy on corn ethanol makes even less sense than it did before. In fact some U.S. corn ethanol plants are going out of business (see here and here).

So, rather than encouraging corn ethanol production to address our energy and climate problems, here’s an idea: push conservation — conservation of carbon sequestering lands by beefing up the CRP acres and conservation of gasoline by enhancing mass transit as well as fuel-economy standards.

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  1. Bill
    Apr 9, 2009

    What about the argument I hear that ethanol doesn’t really displace corn grown for feedstock, because a byproduct of producing ethanol is either wet or dry corn feed for cattle, and is actually better for the cattle than the corn itself. In other words, as long as we eat meat, and grow corn to feed it, we might as well extract the ethanol from the corn before feeding it to the cattle. If that is true, then ethanol would be a net positive, right?

    • Bill Chameides
      Apr 10, 2009

      Bill: If you use some of the byproduct left over from the bio-corn for cattle feed, it definitely improves the overall carbon equation, and you do get a net positive, provided there is no displacement on agricultural lands. That has not been the case thus far.

  2. Barnes Bierck
    Mar 18, 2009

    My understanding is that Brazil’s ethanol production is economically feasible because they use sugar cane, not corn. Louisiana and other southern states do have a lot of sugar, and if we can switch many corn fields over to sugar cane, maybe that will help…it would not hurt to get rid of a lot of the high fructose corn syrup anyway, as it would make us healthier by far. There are many other things to be done, as well, that are challenging from a societal standpoint, but not from a technological one.

    • Bill Chameides
      Mar 19, 2009

      Bill: I’m was suggesting something closer to a zero sum game: take acres out of production by radically reducing our consumption of high fructose corn syrup, which comes from corn, and take some of that and put it to sugar production for making ethanol, which you correctly point out can be economically feasible, as is done in Brazil. A look here:, shows that (in 2007) only about 4% of corn production went to high fructose corn syrup, however. To really take corn fields out of production, we’d need to move toward less meat production, as about 50% (in 2007, according to this source) of corn goes to animal feed. Incidentally, I’m not all that sanguine about the promise of making cellulosic ethanol economically. Saying that “Cellulosic ethanol is on a track to become commercially available in a matter of years.” requires some justification. It’s difficult to really know how long it will be in research stages, and I believe there is no point in counting on it. And burning ethanol from it will still produce carbon dioxide, and there are likely to be waste products just as in other ethanol production methods, including oxygen consuming wastes that could degrade waterways. There are many things that need to be done, such as improving land-use planning and concomitantly making public transportation feasible in places where it currently is not.

  3. Brian J. Donovan
    Mar 17, 2009

    Governor Bobby Jindal has signed into law the Advanced Biofuel Industry Development Initiative, Act 382, the most comprehensive and far-reaching state legislation in the nation enacted to develop a statewide advanced biofuel industry. The legislature found that the proper development of an advanced biofuel industry in Louisiana requires implementation of the comprehensive “field-to-pump” strategy: (1) Feedstock other than corn; (2) Decentralized network of small advanced biofuel manufacturing facilities; (3) Variable blending pumps, in lieu of splash blending, will offer the consumer E10, E20, E30 and E85; and (4) Hydrous ethanol. “Field-to-Pump” is a unique strategy created by Renergie, Inc. to locally produce and market advanced biofuel (“non-corn ethanol”) via a network of small advanced biofuel manufacturing facilities. The purpose of “field-to-pump” is to maximize rural development and job creation while minimizing feedstock supply risk and the burden on local water supplies. For more information, please feel free to visit:

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