In my Nov. 7, 2005, letter to the editor titled "Confusion over Corn," I said it was discouraging to not yet know whether the ethanol produced from corn provided more energy than had been used in producing it (page 4).
The Point/Counterpoint "The Cost of Biofuels" shows that we still don't have a clear answer (C&EN, Dec. 17, 2007, page 12). Bruce E. Dale of Michigan State University says, "Greenhouse gas reduction is also significant." On the other hand, David Pimentel of Cornell University, a longtime critic of ethanol production, says that his analysis of all the energy inputs needed to grow the corn and do the fermentation and distillation steps concludes the energy expended is 40% more than the energy in the ethanol itself.
Other references to this question that I have seen usually indicate a gain, ranging from "marginally better" to the 25% gain reported by Argonne National Laboratory. What I see lacking are data on production of corn, conversion to ethanol, and shipping distances, all of which affect the gain/loss question. It is reported that about half of the proposed plants will use coal as fuel, an energy security gain but a global warming loss. The shipping distance to consumers is important because ethanol cannot be shipped by pipeline.
Do those who see ethanol from corn to be a global warming gain take into account all the numerous inputs that Pimentel does? Does the corn growing result in production of nitrous oxide emission, another greenhouse gas? Has Pimentel brought up to date new efficiencies in corn growing?
The new energy legislation mandates an annual production of 15 billion gal of ethanol from corn by 2022 and provides a subsidy. It appears to me that whether this production helps or hurts global warming will vary among the many plants. It is unfortunate that the general impression among legislators and the public is that this ethanol use will contribute substantially to reduction of greenhouse gases. Thus it takes the pressure off making real progress by other actions.
This is another example of flaws in our proclaimed information age. We have improved the technology for growing corn and for converting it to ethanol. But public knowledge of its relationship to global warming has not kept up with our technological expertise.