Mar 012008
ResearchBlogging.orgIt should be obvious by now that I think today’s is one of the best issues of Science in recent memory. This will be my last post out of this issue, but even these three posts don’t come close to covering everything in there that I think is cool. If you don’t work at an institution that has a subscription, you could do a lot worse for your brain than buying a copy online or at a newsstand or bookstore. So to wrap up my blogging on this one, I’ll cover some papers that support my extreme distaste for biofuel mania, especially with respect to food crops such as corn and soybeans. A pair of articles today find that using food crops for ethanol is even worse in terms of carbon balance than continuing to use fossil fuels.

My regular readers will no doubt be aware that I positively loathe the idea of using corn for ethanol, and am somewhat dubious of the benefits of using even cellulosic ethanol as a biofuel. These are at best stopgaps on the way to fully clean energy sources, do not in general remove a great deal of carbon from the atmosphere, and may have significant adverse effects on the environment and carbon balance. So you should consider this post in light of the significant potential for confirmation bias. That said, these papers seemingly end the debate on the carbon balance benefits of corn or soybean ethanol, and raise serious questions about the benefit of any form of monoculture intended to replace petroleum, especially if they take over cropland or forest.

The fundamental problem with previous models of greenhouse gas reductions due to biofuels, according to the authors of these papers, is that they do not take into account the carbon debt incurred by altered land use. For instance, clearing land to allow the planting of biofuel monocultures has the effect of releasing all or almost all of the carbon presently fixed in plants in those areas (1). Moreover, forward-looking economic models were not previously employed to judge the likely effects of shifting food crops into fuel production. For instance, the increased cost of corn might induce clear-cutting intended to free up more cropland to grow the now more-profitable food crop (2).

What happens when you start taking those “carbon costs” into account? Searchinger et al. find that corn ethanol doubles greenhouse emissions versus petroleum over a period of 30 years and doesn’t break even for 167 years. Fargione et al. predict that it takes 48-93 years, depending on what kind of source land is used, before corn ethanol pays back its carbon debt. And it’s not even the worst: biodiesel derived from lands that used to be rainforest take more than 250 years to balance the carbon sheet, on average. Even cellulosic energy sources, if they are grown on viable cropland, produce more greenhouse gases over the next 30 years than petroleum does (2).

So, are we totally screwed? Not exactly. Both papers suggest that cellulosic sources grown on marginal croplands or prairie, or derived from existing biomass waste (i.e. inedible cornstalks) still end up on the right side of the carbon balance sheet. This is consistent with estimates from a study I discussed previously.

The ideal response to both global warming and oil dependence is to depress petroleum usage (by increasing fuel mileage and encouraging public transit) while transitioning to a completely green transportation system that doesn’t rely on combustion at all. Stretching out oil and growing forests is the best option for slowing emissions short term, and does not require an additional construction of infrastructure to produce and distribute ethanol. If biofuels are unavoidable, however, then they should be derived from non-food crops grown on marginal land if at all possible.

It’s still not clear that biofuels can replace petroleum, so they may not help us as much as we’d like. However, if they are not to hurt us, we must make sure that we make wise choices about what kinds of sources to use and where to grow them. The best evidence now conclusively indicates that ethanol from corn and soybeans (except for cellulosic derived from their spare biomass) is not the way.

1. Fargione, J., Hill, J., Tilman, D., Polasky, S., Hawthorne, P. (2008). Land Clearing and the Biofuel Carbon Debt. Science, 319(5867), 1235-1238. DOI: 10.1126/science.1152747

2. Searchinger, T., Heimlich, R., Houghton, R.A., Dong, F., Elobeid, A., Fabiosa, J., Tokgoz, S., Hayes, D., Yu, T. (2008). Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use Change. Science, 319(5867), 1238-1240. DOI: 10.1126/science.1151861

 Posted by at 3:45 AM

  7 Responses to “Has crop ethanol met its Waterloo?”

  1. I don't feel like my distaste has prevented me from getting informed on this issue. I'm not completely opposed to the idea of biofuels, but in a very short window the initiative on this issue has been seized by agricultural lobbies pushing useless or even dangerous plans. If we cannot implement a biofuel transition in a way that doesn't completely screw us, then it is better not to go that route at all and apply the savings on infrastructure conversion to developing better electric or fuel cell technology.

  2. Well, I focus my discussion on the United States because I live there and also because the US is undeniably the greediest consumer of petroleum products—and the largest producer of CO2—in the world. The vast research resources available there will likely only be turned to biofuel production that can take place in the continental US. That said, I don't think that the problem can be solved in the US alone.

    I should mention that the Fargione article is relatively positive on the prospects of sugarcane, asserting a mere 17 years will be required to repay its carbon debt. However, an analysis similar to that of Searchinger et al. should be used to determine the likely ripple effect of converting arable cropland to sugarcane production (they only analyzed US cropland outcomes). Brazilian sugarcane ethanol may have many of the same problems as corn ethanol in this respect—perhaps even worse ones if rain forest is cut to supplement arable lands overtaken by cane growth.

    Alternatives such as cellulosic ethanol from prairie grasses and agricultural waste seem superior to any form of fruit or nut biodiesel at this point. Unfortunately, the feasibility and efficiency of large scale cellulosic plants has not yet been proven, as far as I know. And all bio-ethanol proposals would require substantial inputs in terms of production and distribution infrastructure.

  3. In keeping with a US-centric post, I doubt sugar cane is as feasible a crop for biofuel in the US as it is in Brazil. The climate and conditions for the plant are likely only found in areas that are already semi-tropical rain forests such as the Southeast. I imagine that would lead to major land use changes for both existing crops as well as forested areas. Sugar cane CAN be grown on marginal land, but only having a limited area in which to grow it, a drought year (such as this one in the Southeast) could be devastating.
    I would think a crop like Swtichgrass (which has a much wider range from Canada to Central America) would be a better investment. Of course we don't yet have the technology to get a viable amount of energy from this yet, but I think it's just over the horizon before we do.

  4. MWC, I'm with you on this one.

    Let me add: We need carbon cap and trade or carbon credits. There is a cost to carbon.

    Once the coal producers (or sugar cane producers) pay for their carbon footprint, that frees up the billions needed to make safe new nuclear (and the research on how to store waste).

    One more thing (having done some analytical work for a non profit alternative energy group, that never went anywhere, now I can use some of the findings): By far –and I mean far — the best way to reduce reliance on petroleum is to get people to stop driving.

    This means remote workers.

    I won't go into all the cultural roadblocks to this, but click around,and you can find answers to most. A job that can be done at a desk can be done at any desk.

    IMO the best thing states could do is have a tax credit for businesses who figure out how to keep up productivity and reduce the amount of time workers spend in their cars.

  5. The way the population is distributed in the US is a major problem in this regard, Swivelchair. It's very hard to get by in the suburbs without doing a lot of driving, even when they are relatively well planned (which is not the case in most places). I totally agree that telecommuting is something that the government should make a serious effort to subsidize and support—that would cut down on a great deal of petroleum use. However, the fundamental problem in the suburbs is that you sometimes have to drive 10 minutes to get to the grocery store, even in a relatively densely populated area. Everything is too spread out.

  6. The idea of working from "any desk" is fine, but is it applicable to what percentage of kind of jobs? For now, mostly intellectual job, I suppose. We will get there some day, but not quite yet…

    As for Brazil ethanol, the research done on ethanol from sugarcane spans at least 30 years uninterruptedly. In resume: Brazil is a unique case that might not be replicated easily. Perhaps not at all and the flex-fuel cars were not even mentioned. while the rain forest deforestation(in Brazil case) is not occurring for that end (ethanol production). It is for the wood, in the first place (there are avid buyers elsewhere in the world, so it is a matter of demand and supply), then the soil is bared and if it is adequate, perhaps soy may come in, but not for ethanol…or cattle grazing that is more likely. This topic is only in its beginnings. The serious discussion has yet to develop. Now, it sounds like speculation, something for policy makers and lobbyist alike taht goes like "Tasting the waters" phase.

    The carbon market is also a hype. I dont buy into it. I am quite suspicious of it. I am for the carbon cap on CO2 that is a much more effective measure and a there should be put in place a more rigorous post-Kyoto protocol where ALL (!!) countries sign in to it.

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