Monday, April 22, 2013

Artificial Fertilizers and Unintended Consequences

Artificial fertilizers are the classic progress trap - innovation leads to higher populations, total dependency on that innovation, and unintended consequences. Which requires us to "innovate" ever faster to avoid the catastrophes precipitated by earlier innovations.

Imagine I had told you at the conclusion of the guano war that we would have the ability to fix nitrogen from the air and distribute it in the ground in unlimited amounts. "All of the world's problems would be solved!" is the cry of the 1890's optimist.

But now we need to feed seven (going to 10-11?) billion people, taking up every patch of arable land, causing deforestation, soil erosion, and mass extinctions, among other things. Plus we are dependant upon rapidly depleting and non-renewable fossil fuels for the process, and rapidly working through our fresh water supplies. And we are creating things like algae blooms, dead zones, and atmospheric emissions undermining the stable climate upon which agriculture depends (exacerbated by the overpopulation caused by the 'success' of agriculture in the first place). Would our 1890's optimist have seen that coming?

So why are today's optimists any different?
Modern agriculture was born when an abundant supply of synthetic nitrogen started flowing at Oppau. The Haber-Bosch process busted wide open the natural limits on plant growth. Nitrogen is a building block of all proteins and other molecules necessary for life, including DNA, and a critical nutrient for all plants and animals. Most of the nitrogen naturally fixed from the atmosphere for plant use is captured by bacteria that grow on the roots of legumes like peas and bean plants. Ammonia is transformed by these symbiotic bacteria into nitrates, which are then taken up by plants. Until 1913, cultivating legumes, recycling manure and crop residues, and mining deposits of bird droppings in South America were the primary sources of nitrogen in agriculture.

Bosch figured out how to react hydrogen culled from natural gas with atmospheric nitrogen at very high temperatures and pressures and in the presence of an iron-based catalyst. The resulting ammonia gas could be easily transformed into ammonium nitrate or urea for use in fertilizers. His work effectively removed the primary limiting factor that kept human populations in check.

Where would we be without this feat of modern alchemy? Well, for starters, many of us wouldn’t be without it: Half of us wouldn’t be alive today if not for synthetic nitrogen.

The Oppau Stickstoffwerke was a kind of existential hinge. In 1913, there were about 1.7 billion people in the world, and the factory fixed about 7,300 tons of nitrogen in its first year. Today there are 7 billion of us and more than 120 million tons of nitrogen are produced every year using techniques that haven’t changed all that much. More than 80 percent of that reactive nitrogen goes into fertilizers for agriculture. A 2008 paper in Nature Geoscience contains a remarkable graph showing how closely world population growth has tracked the increase in fertilizer production—and how a world without it could sustain only 3.5 billion people. That counterfactual can make one’s head swim a bit. It’s like imagining the Back to the Future scenario of your parents never marrying, but on a global scale, or the plot for a Malthusian-themed Newt Gingrich alternative-history novel. Another mind-blowing way to think about it: On average, half of the nitrogen in your body was synthetically fixed.

For this reason alone, the Haber-Bosch process is considered by many scientists and historians to be the most transformational technological development of the modern age. But the case gets even stronger once you consider all of its unintended consequences. For, as with the original Prometheus, progress always comes with a price, in this case water and air pollution, deteriorating human health, reduced biodiversity, soil acidification, and accelerated global warming, to name a few.

Adding all that reactive nitrogen has effectively fertilized whole ecosystems beyond farms’ boundaries, creating a host of downstream and downwind problems. “One atom can have cascading effects on land and water, causing loss of biodiversity, algal blooms,” says Eric Davidson, president of the Woods Hole Research Center and an expert on the global nitrogen cycle, “and the same atom of N keeps getting cycled through the system.”

This nitrogen cascade manifests in a variety of ways. Nitrogen oxides contribute to the production of ground-level ozone, or smog, which increases the risk of serious respiratory illness and cancer; a different problem arises in the stratosphere, where these gases destroy beneficial UV-blocking ozone. Nitrogen fertilizers also stimulate natural bacteria to produce more nitrous oxide, which contributes to acid rain and is a greenhouse gas that traps 300 times more heat per molecule than does carbon dioxide. Reactive nitrogen infiltrates surface streams and groundwater, polluting drinking wells. Excess levels of nitrogen in some ecosystems bolsters some species at the expense of others, leading to overall reduced biodiversity.

Perhaps the most visible impacts are the huge “dead zones” in the Baltic Sea and other areas downstream from farms. One of the worst is in the Gulf of Mexico, where fertilizer runoff carried by the Mississippi River feeds huge algae blooms that deprive other organisms of oxygen. The zone changes in size depending on the flow volume of the river and other seasonal factors. Last year it was about 6,700 square miles—larger than Connecticut.
A Dangerous Fixation. Synthetic nitrogen was born 100 years ago; it’s why half of us are alive. (Slate)

1 comment:

  1. Didn't know about the nitrous oxide holding so much heat. Can we please move on from blaming cattle for the greenhouse gas effect? But then, focusing on nitrogen fertilizer, vegans would have to take responsibility for the damage their holier than thou diet wreaks.

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