Issue Date: January 28, 2008
Point/Counterpoint Versus Readers
I appreciate C&EN's excellent continuing coverage of the biofuels story. David Pimentel and Bruce E. Dale provided diverse views on the possibilities for cellulosic ethanol (C&EN, Dec. 17, 2007, page 12). Among Dale's comments were that "Cellulosic ethanol could eventually supply hundreds of billions of gallons of liquid fuel at costs well under $1.50 per gal of gasoline equivalent"; "1,500 gal per acre is a feasible 10-year goal"; and "Perennial grasses are excellent builders of soil, and they sequester large amounts of atmospheric carbon dioxide. They also trap inorganic nitrogen in plant matter." C&EN is not a peer-reviewed journal, but still.
The first and second claims are extravagant, and the third suggests that the perennial grasses fix nitrogen as do the legumes, which they do not. Of course, these plants fix large amounts of atmospheric carbon dioxide, but it is rapidly returned to the atmosphere—much of it during fermentation of the cellulose-derived glucose (one-third) and the rest during combustion of the ethanol. Production of the requisite grass sources of cellulose would require destroying millions of forested acres. These forests serve not as temporary, but as crucial long-term and continuing carbon stores.
Switchgrass, most prominently mentioned as the cellulose source, contains only about 30–40% cellulose; nearly as much largely nonfermentable hemicellulose; and significant levels of lignin, protein, and alkali ash. What would be done with the millions of tons of these by-product materials?
Less than 5 billion gal of ethanol from corn was produced in 2006. Runoff of excess nitrogen and phosphorus from fertilizing the requisite corn crop has already contributed to the "dead zone" in the Gulf of Mexico. Given the recent budget approval for more than tripling the production of ethanol from corn, and given the massive projections in the first and second claims above, further environmental damage can be anticipated. Perhaps the high investment in subsidies and research in these areas should be mostly directed to renewable sources such as solar cells, as Pimentel suggests. Along with major mandates for conservation, such a redirection would help lead us to both energy and environmental security.
Landis W. Doner
Corn ethanol has been controversial for many years and still is. The Point/Counterpoint presented in C&EN does not resolve this issue because Dale and Pimentel talked past each other for the most part. I am inclined to believe Pimentel is correct, even as I do not accept his numbers at face value.
There is a way for Dale to prove both Pimentel and me wrong. Dale asserts that corn ethanol is an energy plus. To prove this, all he has to do is encourage ethanol producers and those who provide inputs to growing and processing the corn to use only the created ethanol as their energy source. No petroleum, coal, methane, or propane to produce fertilizer; no diesel to fuel the irrigation pumps; no propane to dry corn; no grid electricity to run the plants but only that using electricity from dynamos powered by ethanol; no diesel or gasoline for the delivery trucks—just ethanol. (I'll concede them the 15% gasoline for the E85 fuel but will take it into account in the final analysis.)
Then, if there is still ethanol left to fuel our cars, Dale wins. If this can't be done, Dale loses and Pimentel wins.
We can argue about the energy balance and other factors until we are blue in the face. The only valid argument is economic. The market cost of ethanol encompasses all value inputs, including materials and labor. That cost exceeds that of gasoline, hence the subsidy of 51 cents per gal, without which no ethanol would be blended into gasoline. Using corn ethanol as a motor fuel is a losing proposition, even if the loss is only the taxpayer's.
Ethanol from sugarcane molasses may have favorable economics but would require duty-free imports of Brazilian ethanol. That we should tax imported ethanol and subsidize domestic is clear proof, if any is needed, that politics—not economics or patriotism—moves this boondoggle. Corn and sugarcane growers and processors have more clout than the rest of us. They are the only beneficiaries.
Regarding ethanol as a suitable fuel for internal-combustion engines, experts tell me that it does not work in diesel engines, which consume some half of our liquid fuel.
A well-proven process to convert coal into liquid hyrocarbon fuel exists. It is used in South Africa and was used by Germany to power its war machine. It is supposedly economical when crude oil costs more than $50 per barrel. This process may be worth a serious look.
A. E. Lippman
It seems impossible to untangle the complex, convoluted pros and cons argued by Dale and Pimentel, especially as the exchange starts to become personal rather than sticking to the subject. But are not the trees getting lost in the forest?
Corn ethanol requires water to grow the corn, on that I think all must agree. No water, no corn; no corn, no ethanol. What happens not if, but when, there is a prolonged period of drought, maybe one year, maybe several? It happened in the 1930s "dust bowl" and is happening now in large parts of the Southeast. All of the arguments about energy content, etc., become moot if there is insufficient raw material. Corn, at the mercy of the water supply, is not a reliably stable energy source.
G. Vincent Calder
I want to express my view that Pimentel won the debate over biomass replacing petroleum, even in part, in the near future. I suppose if some low-cost enzyme or other catalyst were available to convert cellulose to glucose despite the lignin complication, the use of biomass as a practical energy source could not be ignored. Grazing animals and termites accomplish this routinely, of course.
I'd like to suggest that C&EN do more of these important debates. Both sides raised excellent points. Why not give readers, especially online readers, a chance to vote on the issues after reading the articles? Since a lot depends on debating skills and accuracy of the data presented as well as the overall perspective of the writer, I'd also like to see what some think tanks have to say about key issues. In fact, it might be instructive to run this specific article past a couple of such groups to get their impressions.
In this debate, a key factor seems to be the perspective that even if we converted all of our corn to ethanol, it would replace only a small percentage of our fuel needs.
Kenneth A. French
Pimentel errs in citing the production of CO2 during fermentation as contributing to the CO2 burden in the atmosphere. The error lies in the fact that the carbon was extracted from the atmosphere by the growing corn plant. That CO2 release does not add to atmospheric CO2; it merely replaces a fraction of that which was removed by the crop. This error raises concerns about the validity of some of his other points.
C. Clinton Rila
Mount Pleasant, Iowa
Driving east from Denver into western Kansas last August, I saw corn "as high as an elephant's eye" stretched from horizon to horizon and from north to south as far as the eye could see. It appeared that these farmers had bought into the corn-for-ethanol economy in a big way. The popular press alternately declares that food prices are increasing because the corn crop is being diverted from food and feedstock to fuel ethanol or insists that the U.S. must use biomass for ethanol production to free ourselves from foreign oil dependence.
Therefore, I was happy to see C&EN treat this fraught subject. After reading the Point/Counterpoint discussion, I did not feel informed but rather annoyed by the rhetoric, the repetitive argumentation, and the lack of civil discourse between Dale and Pimentel. Of course, one cannot equate the cost of a ton of coal with a "ton" of oil used in the production of a "ton" of ethanol from biomass. Of course, one must account for the total cost of that "ton" of ethanol, including the costs of fertilizers and running the farmer's tractor.
Here are two questions, among many, that I would like to have answered: First, on the economic front, what is the cost-now and 10 years from now-of putting a gallon of fuel containing x % ethanol in my car versus the cost of a gallon of gasoline without ethanol? Second, on the environmental side, how many miles per carbon atom can I expect to obtain, in the same vehicle, comparing "x % ethanol-containing" versus "pure" gasoline?
As a scientist, I need some talking points for discussing biomass-to-biofuel conversion with my scientist and nonscientist colleagues. What are the real costs in economic and environmental terms? What are the benefits? How will these processes help achieve national energy security in the U.S.? Editors, please find an independent agency or group to address this important topic.
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