Argument: Corn ethanol is inferior to cellulosic ethanol

Issue Report: Corn ethanol


Corn ethanol is presently the only commercially viable means of ethanol fuel production. It’s made by distilling fermented simple sugars derived from corn. The problem is, it’s still an environmentally taxing process.
‘With ethanol, the devil is in the details,’ says Dan Becker. ‘There are ways of making it that are quite clean, but that’s not the way we’re doing it.’
Becker backs cellulosic ethanol. If researchers can streamline what’s still an experimental process, then ethanol could be made from a variety of plant materials.
The benefit of that, Elizabeth Marshall says, is that cellulosic ethanol production would allow farmers to grow crops that work in their area, rather than forcing corn on lands that are not well-suited to support it.”
  • “Ethanol: Energy well spent”. Natural Resource Defense Council. February 2006 – “Cellulosic Ethanol Studies we reviewed four studies published since 1990 that examine the energy return on investment for cellulosic ethanol. These included studies authored by Tyson et al. (1993), Lynd and Wang (2004), Sheehan et al. (2004), and Pimentel and Patzek (2005). Similar to our review and comparison of the corn ethanol studies discussed above, we calculated energy return on investment of ethanol ourselves, using the nonrenewable energy input value specified by the authors of each study and a common energy output value per liter of ethanol. In contrast to the corn ethanol studies, where all researchers modeled starch ethanol manufactured from corn, the research teams in these studies each modeled different crops.
Of the four studies we reviewed and compared, again all but the Pimentel and Patzek study show substantial renewable returns on nonrenewable energy investment to the production process. Energy return on investment values for these three studies ranged from 4.40 to 6.61, significantly higher than the energy return from corn ethanol. The wide variance of these numbers is consistent with the developing nature of cellulosic ethanol technology and the wide variety of feedstocks available. The significantly lower renewable energy return contained in the Pimentel and Patzek study can be attributed to these researchers’ assumption that the industrial energy for manufacturing ethanol would be produced by fossil fuels and grid electricity, rather than by combustion of the lignin that comes to the production facility as part of the crop. All well-developed models of cellulosic ethanol production assume that industrial energy will be produced by lignin combustion – in fact, in most models the heat released by lignin combustion actually exceeds the heat required by the industrial process and can be used to generate surplus electricity.”
  1. Virtually no fossil fuel is used in the conversion process, because waste biomass material, in the form of lignin, makes an excellent boiler fuel and can be substituted for coal or natural gas to provide the heat needed for the ethanol process.
  2. Farming of cellulosic biomass is much less chemical- and energy-intensive than farming of corn.
  3. Perennial crops store carbon in the soil through their roots, acting as a carbon “sink” and replenishing carbon in the soil. Switchgrass, for example, has a huge root system that penetrates over 10 feet into the soil and weighs as much as one year’s growth aboveground (6-8 tons per acre).”