Ethanol, the characteristic solvent for social distance and shellac, is also a motor fuel with attractive characteristics: it's made of sunshine and exactly the CO2 we like to take out of the atmosphere, it increases gasoline octane as an additive, it's environmentally quite benign in spills and such, and it's not imported from places with fractious and prickly governments.
However, it doesn't just dribble out of corn plants: to get ethanol requires growing plants (fertilizer, tractor fuel...), hauling corn to a distillery, smooshing it up with yeast and keeping it warm (more fuel), distilling the alcohol out of the mush (more fuel), and various other industrial operations all of which use energy. A debate has been burbling for several years about whether we really wind up ahead in various important ways by substituting ethanol for gasoline in cars, and the issue has been confused by the patchwork of subsidies and regulations that distort market prices for fuels of all kinds.
A gang at the Energy and Resources Group and the Goldman School at UC Berkeley, namely Alex Farrell, Richard J. Plevin, Brian Turner, Andy Jones, and
Dan Kammen, who invited me to play with them over the summer and fall while we did the project, have clarified things greatly. In my view our most important finding is that the "net energy" measure, which looks only at the fossil fuel energy consumed to make a unit of energy in the form of ethanol, asks the wrong question. For example, if ethanol provided a means to take 100 joules of energy from coal and obtain 50 joules worth of ethanol, it would not necessarily be a bad idea. Coal is abundant and cheap; the problem with it is that when burned, it releases the "greenhouse gas" CO2. So one would want to ask about the greenhouse gases released (and other costs, of course), not the net energy, and if the CO2 from burning the coal were captured and sequestered, this notional technology would be a prima facie policy winner, allowing us to run cars cleanly on domestic abundant coal rather than imported, scarce petroleum.
Our article in Science (Farrell et al) is behind a paywall (today's issue, if you have access to it) but also posted here, with the analysis behind it. This LA Times story is a pretty good report. What we found, adjusting six studies of ethanol input demands so they could be compared, is that ethanol from corn (maize) as we make it today is a big petroleum saver, and offers modest gains in global warming, compared to gasoline. The specific technology used to make it matters a lot, but what matters more is the crop you start with: ethanol from grass or wood will be a very attractive fuel on energy, global warming, and petroleum displacement grounds.
We are beginning a research initiative that will give us a better look at other considerations like cropland fertilizer runoff, soil protection, and forest conversion to farms. The larger policy debate will be much occupied with conflict between the farm community already in the corn business and quite enamored of the subsidies and regulations that favor it, and the nascent industry of cellulosic ethanol; watch this space for updates.
