Alligator Diesel
The idea of using the fat from farm-raised alligators as a source for biodiesel is fascinating. The main problem with biodiesel from soy has been the land-use impact, which is huge. A recent study done by Clint Andrews and colleagues for the Lincoln Institute of Land Policy‘s 2010 Conference on Climate Change, Environment, and Land Policies evaluated the land-intensity of a variety of energy sources, both conventional and alternative. Biofuels in general had the highest land usage, but soy biodiesel in particular was way beyond any other energy source:
That’s right, using soy biodiesel for all of the world’s energy demand would require several times the amount of currently cultivated land for all crops to be devoted to soy. Obviously that’s an extreme and implausible scenario, but it gives a sense of the scale of land-use impacts associated with biodiesel from soy.
There have been some concerns with biofuels in general over whether they are actually carbon-neutral. This has been particularly unclear with wood, since trees can live a long time so it’s not necessarily the case that the carbon dioxide released into the atmosphere from burning wood has only been taken out of the atmosphere recently, which is necessary for biofuel use to not increase atmospheric carbon concentrations. With soy this isn’t really a problem, since it is grown and harvested over a short period.
It’s not totally clear to me where alligators fall in regard to these problems. If they are harvested at relatively young ages (compared to trees) they would cause few problems with carbon concentrations. Alligator farms also presumably take up less land than soybean fields, though it would be good to get some data on this. The NYT blog post on this discusses the amount of fat that could be rendered but that is currently thrown away, estimating a final volume of 1.25 million gallons of fuel from 15 million pounds of fat discarded a year. That sounds like a lot, but both the journal article and the blog post note that current US diesel consumption is about 45 billion gallons a year. Thus, even if all the alligator fat that is currently thrown away were converted to biodiesel it would be a drop in the bucket compared to the total demand. This implies that if the production process proves to be economical, and demand for alligator diesel develops, the scale of alligator farming could increase immensely. Figuring out the land-use and other implications of that would be an important task before anyone gets too carried away with this admittedly fascinating research.
Ayalasomayajula, S., Subramaniam, R., Gallo, A., Dufreche, S., Zappi, M., & Bajpai, R. (2011). Potential of Alligator Fat as Source of Lipids for Biodiesel Production Industrial & Engineering Chemistry Research DOI: 10.1021/ie201000s
