A number of people picked up on my post lambasting biofuels, Like Easter Island, only with cars. I'm going to add to this analysis by turning to perhaps the main skeptic of the biofuels story, David Pimentel, a Cornell University scientist, and his take on ethanol. (Thanks to Mobjectivist for pointing me in this direction.)
Pimentel's 2003 survey of ethanol energy studies demonstrates among other things that ethanol is a big net energy loser. It takes 123,696 BTUs to make one gallon of ethanol which contains only 99,119 BTUs of energy. Pimentel observes in another piece on his work that if ethanol were a big net energy gainer, then it would make economic sense to run the plants that make it on ethanol. Of course, all those plants are run on fossil fuels, either directly through burning or indirectly through the production of electricity. And, even the latest estimates that Pimentel presents don't include the energy costs of building ethanol plants (something his critics also leave out of their calculations). Pimentel also assumes that the energy value of co-products such as animal feed which are left over from the production process are probably negated by the pollution associated with that production. Even when their energy value is included, ethanol moves from an energy loss of 29% to a loss of 20%, hardly the answer to our energy future. Finally, he makes a compelling case that corn--at least the way we currently produce it--is not a renewable source of anything in the long run when you consider soil erosion and degradation, water pollution from pesticides and fertilizers, and widespread irrigation which will ultimately use up groundwater in the Plains states while increasing soil salinity to the point where soils become barren (a growing problem throughout the farm belt). He adds that a substantial increase in acreage for corn devoted to ethanol would have profound effects on food production and prices.
To give you an idea of how ethanol proponents think, in a 1995 USDA study the authors seem to be aiming at a different mark. They claim that ethanol will replace 7 gallons of imported crude oil for every gallon of ethanol produced. This is because they estimate that 85 percent of the energy needed to produce ethanol comes from domestic sources such as coal and natural gas. This may be an argument for energy independence, but it's not one for energy efficiency. The authors estimate that with co-products ethanol provides 1.24 units of energy for every unit expended to make it. Without figuring the co-products the number is 1.01.
First, the co-products may be useful, but they aren't fuel. Second, we ought to consider that the energy profit ratio for oil, which ethanol is supposed to replace, is about 20-1 for old discoveries and about 8-1 for new discoveries. (The energy profit ratio is the ratio of energy output for each unit of energy input.) This is what we run our economy on. If we expect to replace it and continue on the economic growth trajectory the world is currently on, it stands to reason that we will need to find something that provides a similar energy profit ratio or become 8 to 20 times more efficient in our use of fuels or a combination of both. And, we would need to start making this transition very soon in order to prepare our whole transportation fleet in order to head off emerging energy shortages.
Now, back to reality. Even if we were to concede that ethanol and other biofuels are net energy sources, an energy profit ratio of 1.01 or 1.24 just won't get it. We'll be much better off creating genuinely renewable energy; making our households, our transportation system and our businesses much more energy efficient; and downscaling all of our institutions so that we will be able to live and work in a more localized, lower energy-intensive economy.
(Comments are open to all. See the list of environmental blogs on my sidebar.)