Mar 132008
 
I know, I know… you’re pretty darn sick of seeing me beat up on corn ethanol in this space. To be honest, I’m a little sick of it, too. However, the idea is so appealing on its surface, so desirable to the agricultural lobbies, and so pernicious in its environmental effects that I feel I have no choice but to do whatever I can to publicize the very good research indicating its flaws and dangers. Increasing awareness of the problems associated with corn ethanol mandates is the only way to kill that horse and make it stay dead. The corn ethanol lunacy of our would-be Presidents was most clearly on display before the Iowa caucuses, but don’t think just because the politicians aren’t talking about it that the issue has gone away.

So that’s why I’m talking about a paper (now in PNAS preprints) by Simon Donner and Christopher Kucharik on the effect of corn ethanol on the oceans (1). Given that we do not actually grow corn in the ocean, this might seem like a bit of a stretch. But the existence of rain and rivers means that what we put in the soil almost always ends up in the sea, where it often has significant effects.

The problem corn causes for the ocean is hypoxia. As you should be aware, there is an enormous (>22,000 km2) seasonal hypoxic region or “dead zone” in the Gulf of Mexico. Fresh water efflux from the Mississippi bearing significant concentrations of nitrogen-rich fertilizer is believed to cause the hypoxia primarily through eutrophication. Beyond being undesirable on its own merits, the dead zone puts fisheries at risk, and eutrophication can contribute to toxic algal blooms. So whether you care about the environment or the economy of coastal regions you have good cause to want to mitigate nitrogen fertilizer pollution.

But that’s a problem, because corn is a pretty fertilizer-intensive crop. Given that making ethanol for transportation from corn starch will probably require a significant increase in corn production, Donner and Kucharik asked what effect the changes in agriculture would have on the amount of dissolved inorganic nitrogen (DIN) exported to the Gulf of Mexico. I have shamelessly stolen the figure to the left for your benefit. As you can see, they tested their forecasting model against several scenarios. The control was just to check export for the years 2004-2006 using the model against known data. The 2007 column is a prediction for last year. Then they get to the models forecasting export in the case of 15 billion gallons of production under two land-use scenarios, and a situation where radical changes in land use allow the production of all 36 billion gallons of mandated biofuels as ethanol from corn. As you can see, none of these situations even come close to reducing DIN to desired levels, though arguably the “optimistic” (left) 15 billion gallon scenario isn’t too much worse than the status quo.

Of course, there is that last one, which reflects a Panglossian possibility in which red meat production is cut in half, the corn once destined for feed is repurposed for ethanol, and wetlands that filter out 35% of DIN are created around all corn and soybean farming land. Basically, this plan depends on a dramatic increase in the popularity of vegetarianism, as well as some extremely unrealistic behavior by farmers and federal land planners. The upshot of it all is that reaching biofuel production goals through corn ethanol is almost certain to increase the amount of nitrogen reaching the Gulf. Of course, this is a computer model of future outcomes, and as such, the results reflect the assumptions made in the construction of the model. However, the authors generally appear to err on the side of favoring ethanol. In the “optimistic” 15 billion gallon model, for instance, annual yields continue to increase without any additional fertilizer use per plot.

Of course, this will be a problem for other biofuels as well. Switchgrass can be grown on marginal lands with decent yields. However, biofuel demand will create an economic incentive to improve output; one convenient way to do this is to fertilize. Even if a relatively small amount of fertilizer is used on every switchgrass plot, that will still be an enormous increase over the amount of fertilizer used on those plots previously (i.e. zero). The ill effects of poorly-conceived biofuel initiatives will not be limited to economic disruptions and increases in greenhouse gases—enormous tracts of biofuel monocultures will have pronounced effects on ecosystems nearby and downstream. Before we take the plunge on massive initiatives we need to study the outcomes, and ask whether what we are doing achieves more harm than good. Too bad our would-be leaders only seem interested in pandering for votes and campaign funding.

1. Donner, S.D., Kucharik, C.J. (2008). Corn-based ethanol production compromises goal of reducing nitrogen export by the Mississippi River. Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0708300105

 Posted by at 3:00 AM
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
Jan 152008
 
Blogging on Peer-Reviewed ResearchWith the Iowa caucuses over, the corn ethanol mania that seized the campaigns of candidates from both major parties appears to have passed. This can only be a good thing, because producing ethanol from corn starch is an ecological and agricultural dead end. But the siren song of biofuels continues to beckon, with cellulosic ethanol from switchgrass now being the alcohol du jour. Cellulosic ethanol has tremendous advantages, not least that if cellulosic facilities are the basis of our alcohol infrastructure then practically any vegetation can be used to supply them. Switchgrass, because it is high in cellulose, simple to cultivate, and can be grown on reserve plots, is a tremendously attractive plant to serve as the backbone for such a system. However, research on the full-scale feasibility and energy output from switchgrass cultivation has been lacking. Last week, that deficiency was addressed when PNAS released a study from the U.S. Department of Agriculture and University of Nebraska claiming that the energy output from switchgrass ethanol was more than 500% of the energy put into making it. The article is open access, so you can go on over to PNAS and read it yourself if you like. The findings of this article are encouraging and promising, but it is the start, not the end, of the necessary research.

Assuming that the production and distribution of a biofuel are feasible—this is not a minor assumption—the ultimate decision of whether we should wholeheartedly pursue biofuel production and if so what approach to use should be decided by the answers to the following questions, based on our strategic and environmental needs:
  1. Does the biofuel produce substantially more energy than is needed to generate it?
  2. Can the biofuel significantly reduce or eliminate our dependence on petroleum?
  3. Do production and use of the biofuel add less greenhouse gases to the environment than they remove?
  4. Does the biofuel produce fewer non-greenhouse pollutants than petroleum products?
  5. Can the biofuel be produced without significant disruptions to agriculture or the food supply?
  6. Are the other negative environmental effects of biofuel monoculture manageable?

Obviously, we want every answer to be “yes”, and a little quick thinking will show that switchgrass scores higher than corn ethanol on questions 5 & 6, with a tie on question 4, and less clarity on questions 1-3. Question 2 doesn’t really get a good answer in this paper (so far the answer is “no”), but questions 1 & 3 are treated, albeit incompletely.

The authors of this study answer question 1 with a resounding yes, claiming that the switchgrass fields produced an astonishing 540% more energy than was used in seeding and maintaining them. Given that it is still not clear whether corn ethanol is capable of breaking even on this kind of energy balance, that seems like an end to the question. It’s important to realize, however, that no energy was actually produced in this study, because no large scale cellulosic ethanol plants actually exist. This would appear to be a significant advantage for corn—although its production is less energy efficient, such production is at least not fictional. The energy numbers and ethanol yields in this study emerge from a computer model based on pilot studies; the efficiency of cellulosic ethanol plants on a large scale, though promising, has yet to be demonstrated. As such, this number should be taken with a grain of salt.

The energy numbers for this comparison also do not appear to include the diesel used in agriculture or any estimates of energy costs involved in transporting the substantial quantities of biomass to ethanol plants. The latter is either totally outrageous or completely fair; one of the uncertainties in treating this question is the infrastructure that would be developed. If most ethanol production ends up in large centralized plants the transport costs will be high and the energy efficiency per year will be less. On the other hand, if ethanol production is distributed to many small local plants the energy costs of transport will be diminished while the costs of start-up in terms of materials, money, and energy will be high. This question is significant and one that needs an answer quickly; fortunately, given ballpark figures for energy consumption and output it should be relatively easy to model computationally. That said, I doubt any two models will agree.

So, this study has many nice things to say about the energy yield of switchgrass ethanol, but no experimental proof. But what about question 3? Here again the authors have nice things to say. Most of the plots were carbon-neutral, with slight deviations up or down in different years. Of course, this is again the result of a model; the final answer will depend to a large degree on how effectively carbon can be sequestered in the soil and how much energy the burning of the lignaceous or woody portion of the biomass can contribute to the production process and energy grid.

However, our joy at finding a carbon-neutral fuel should be tempered by remembering that the problem with greenhouse gases is that they are too concentrated in our atmosphere. This is important, so I will repeat it in larger text with a color accent:

The problem with greenhouse gases is that they are too concentrated in our atmosphere.

That is to say, the problem is not that we are adding more greenhouse gases, the problem is that the atmosphere has too much greenhouse gas already. While adding more certainly makes that problem worse, adding nothing does not make it better. Those poor plants and animals got buried underground and hid their carbon away from the world for millions of years; until we put it back where we got it, our climate will be altered. Thus, what we require is permanent sequestration, something that cannot be achieved to any meaningful degree by biofuels.

I’m being mean to switchgrass, of course. Every biofuel fails this test, but so far switchgrass comes closest to success, and the most optimistic estimates certainly seem to indicate that a substantial quantity of carbon would be sequestered in the soil. As the transit system switched over to renewable fuels that advantage would be increased. Biofuels can stop or slow global warming, but they cannot turn back the carbon clock.

So, is this study worthless? Not by a long shot. However, the real contribution of this study is not in its publicized conclusions: they are largely based on modeling and possibly overstated. No, the great contribution here is the substantially more detailed assessment of the required inputs for producing switchgrass biomass on a large scale. The ratio of inputs to outputs was far smaller than expected; from this work it appears that switchgrass cultivation will be more energy-efficient than previously suspected. However, even in this regard the study is limited: the geographic area studied was small and not particularly diverse in climate. It remains to be seen whether switchgrass cultivation will be as effective in warmer or drier climates.

Nonetheless, this study, and others like it, are precisely what we need: detailed research dedicated to finding the best answer. Yet this sort of critical assessment will be all too infrequent in the coming year, as bloviating presidential candidates lurch from hot topic to hot topic, and our useless, brainless Congress lards the budget with pork based on speculation rather than research to find facts.

M. R. Schmer, K. P. Vogel, R. B. Mitchell, and R. K. Perrin, “Net energy of cellulosic ethanol from switchgrass.” Proceedings of the National Academy of Sciences 15 January 2008 pp. 464-469 DOI: 10.1073/pnas.0704767105

 Posted by at 3:00 AM