Thursday, January 26, 2006

Peak Oil and Fertilizer

In an essay I routinely assign to students, Richard Manning writes.
Every single calorie we eat is backed by at least a calorie of oil, more like ten. In 1940 the average farm in the United States produced 2.3 calories of food energy for every calorie of fossil energy it used. By 1974 (the last year in which anyone looked closely at this issue), that ratio was 1:1. (Manning 2004)
I had always assumed that a significant portion of the oil used in the production of food was used in the production of nitrogen fertilizers, and that the guaranteed rise in oil prices in the coming decades would hurt conventional agriculture specifically by cutting off the flow of nitrogen, a cycle in which 1% of the Earth’s primary energy productivity goes to feed 40% of the human population (Smith 2002).

I should have realized, though, that the picture is more complicated. “Peak oil” is the name given to the prediction that that the production of oil over time follows a bell curve pattern, with a peak that will occur in the near future or perhaps has happened in the recent past. Life on the down slope of that curve will be increasingly difficult, and should be feared much more than possible end of oil production altogether. So what would be the effect of peak oil on fertilizer production?

Fertilizer production accounts for 28% of all the energy used in agriculture, but the limiting input to fertilizer production is not oil, or even fossil fuels, per se. The important input is hydrogen. Nitrogen fertilizers are made from ammonia, which for nearly a hundred years has been synthesized using the Haber-Bosch process. The Haber-Bosch process makes ammonia from hydrogen, nitrogen from the air, and an iron catalyst. Since the 1960s, most of the hydrogen for this process has come from reformed natural gas. Since the mid-70s it has been unprofitable to use fuel oil for this process. (See this UN document.)

Several factors mitigate the threat peak oil poses to fertilizer production. The first is simply that the relevant peak is not oil, but natural gas. Natural gas production will also peak, but the peak is generally thought to come about 10 years after the oil peak (see e.g., here which buys us some time. Second, hydrogen does not have to come from reformed fossil fuels at all. Hydrogen can be made by electrolyzing water, using electricity from the greenest of sources, like wind or solar. Proponents of hydrogen fuel cells are fond of emphasizing this point, and most talk of a coming “hydrogen economy” assumes that solar or wind will be used to create the currency for this new economy on a large scale. If these predictions are correct, then nitrogen fertilizers will actually have a comfortable place in the post oil world. Finally, biotech may wind up contributing a lot to fertilizer production in the future. Legumes fix nitrogen because they have a symbiotic relationship with bacteria that produce the enzyme nitrogenase. Nitrogenase also makes ammonia from atmospheric nitrogen, and we are beginning to understand more about how it works its magic. One of the articles I found while googling around on this topic is a report in Science identifying the three dimensional structure of nitrogenase (Einsle et al 2002) along with the comprehensible to outsiders write up of the report (Smith 2002). Genetic engineering has long track record now of creating microorganisms that produce useful chemicals. In the future, ammonia may be on the list.

Another interesting post I found while googling around compares peak oil to the Y2K scare. “Y2K?” you ask, “wasn’t that a lot of people getting all freaked out over nothing?” Not the way Jamais Cascio sees it. He says Y2K was an example of people getting all freaked out, organizing a global response, and averting disaster. When the levee holds, everyone assumes that there was no danger, and the levee builders where upset over nothing. Perhaps even the money spent on fortifying the levee was wasted. The levee builders know better.

I think there is a good chance Cascio is right. There are a lot of problems raised by peak oil that we can avert if we get freaked out now.


Einsle, Oliver, F. Akif Tezcan, Susana L. A. Andrade, Benedikt Schmid, Mika Yoshida, James B. Howard, and Douglas C. Rees. 2002. Nitrogenase MoFe-Protein at 1.16 Å Resolution: A Central Ligand in the FeMo-Cofactor. Science 297 (5587):1696-1700.

Manning, Richard. 2004. The Oil We Eat: Following the Food Chain Back To Iraq. Harper's Magazine, February.

Smith, Barry E. 2002. Nitrogenase Reveals Its Inner Secrets. Science 297 (5587):1654 - 1655.

No comments: