So there's an acute fertilizer shortage. The big problem is a lack of nitrogen which, although it accounts for most of the atmosphere (78.1 percent), is notoriously tough to "fix," since it's got those pesky triple bonds. One of the unsung heroes of modernity is the Haber process, which makes nitrogen-rich fertilizer by heating, under high heat and pressure, nitrogen and hydrogen.

The Haber process now produces 100 million tons of nitrogen fertilizer per year, mostly in the form of anhydrous ammonia, ammonium nitrate, and urea. 3-5% of world natural gas production is consumed in the Haber process. This fertilizer is responsible for sustaining one-third of the Earth's population.

Ok, so the Haber process (which was originally invented to help Germany produce explosives during WWI) requires lots of energy to fix nitrogen. But here's my naive question (and keep in mind that I'm really ignorant when it comes to fertilizer and nitrogen fixation):

Lots of different prokaryotes fix nitrogen for us, most famously the legumes with their symbiotic bacteria. What's their enzymatic secret? Why can these single celled creatures break apart the strong bonds of nitrogen but we can't? (Unless we consume huge amounts of energy.) I mean, if we could find a way to emulate the genius of natural selection, we could instantly eliminate a significant share of natural gas consumption. That seems like a scientific breakthrough worth investing in.* So what's the stumbling block?

*Of course, I know it's much more important to give Americans a summer without a gas tax.

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Nitrogenase research is a pretty active field, and lots of scientists would certainly like to emulate it's mechanism for our own sordid needs. Sadly, the mechanism of catalysis is still not fully understood (and it's very complex), it's not an especially fast or high yield enzyme (generally), and worst of all it is very sensitive to oxygen. Check out some of the references in wikipedia for a starter.

By Chris Jeans (not verified) on 30 Apr 2008 #permalink

Wow, wikipedia pages like the one for nitrogenase make me love wikipedia. Such a lucid breakdown of all the technical difficulties. Thanks for the tip.

Since I started writing about biofuels, I have thought an unexploited niche would be the manufacture of ammonia from biogas to replace the natural gas that is now used. I think that is a more likely short term solution compared to teasing out the nitrogen fixing bacteria's secrets.

By justawriter (not verified) on 30 Apr 2008 #permalink

I mean, if we could find a way to emulate the genius of natural selection, we could instantly eliminate a significant share of natural gas consumption.

Or we could change our agricultural systems to more resemble natural ecosystems, which has the advantage of actually being do-able now. There are all sorts of nitrogen fixers you can use in a rotation, and there's quite a lot of interest in the use of permanent or semi-permanent undersown clover swards in various agricultural systems right now, which has the advantage of not having to take land out of production for a season. Polyculture design has a huge amount of potential. Heck, various civilisations had very highly developed and productive polyculture agricultures before the missionaries showed up with their smallpox and their Biblical injunction against growing more than one crop in a field at a time.

Almost the entire development of modern agriculture has been the story of using chemical engineering to try and overcome the core problems in a system of agriculture developed in the early 18th century by a man who thought that plant roots consume the soil through little mouths. While Jethro Tull's ideas were a huge improvement on the agricultural practices of 17th century England, they're not a patch on some of the ideas of the Aztecs, and they're certainly not what you'd come up with starting from scratch with a modern understanding of plant nutrition and ecology.

Evolution has already solved all these questions. We just need to learn how to utilise the available solutions better.

It strikes me that there is a huge amount of fixed nitrogen going down the sewers of every city in the world. Is there some way to recover large amounts of that at our already existing sewage treatment plants?

The chinese solved the problem brilliantly through incorporating the ecology of mulberry trees, silk worms, rice paddies, cyanobacteria, and fish. The droppings from the silk worms that feed on the mulberry trees (which consequently are a fruitful harvest) fall into the water. The cyanobacteria in the rice paddies fixes the nitrogen in the droppings, essentially fertilizing the water for rice growth. They also practiced aquaculture with the harvesting of fish that would feed on potentially destructive rice pests. Trophic solutions are the best!

By oliver hulland (not verified) on 04 May 2008 #permalink