Fertilizer, fertility, and the clashes over population growth
On May 12, 1907, toward the end of the annual meeting of the German Bunsen Society, which was held that year in Hamburg, a distinguished chemist named Walther Nernst insulted a not so distinguished junior colleague named Fritz Haber. The topic of the put-down-the synthesis of ammonia at very high temperatures-was, even by Bunsen Society standards, abstruse, but the gibe was strongly worded, so everyone at the meeting understood Nernst’s intent. Haber, who suffered from a variety of nervous ailments, was mortified. When he returned home to Karlsruhe, his skin broke out in hives. Before Nernst’s attack, he hadn’t been all that interested in synthesizing ammonia. The insult had the unintended consequence of stiffening his resolve. Haber threw himself full time into proving that ammonia could indeed be cooked up in the laboratory, using hydrogen and ordinary nitrogen gas. The result of this effort, which eventually became known as the Haber-Bosch process, had unintended consequences of its own, some of which proved to be world-altering.
Nitrogen is a tease. It’s crucial to life but exists mostly as N2, a form that living things can’t make use of. Early in the history of agriculture, people realized-without, obviously, understanding the chemistry behind this insight-that when usable nitrogen ran low fields turned barren. Eight thousand years ago, farmers in the Middle East were already planting legumes, whose roots harbor nitrogen-fixing bacteria, in rotation with cereal crops, such as wheat. Later, Cato the Elder recommended that Romans “save carefully goat, sheep, cattle, and all other dung.” Bird shit is an excellent source of nitrogen, and in the early nineteenth century, when Europeans learned that there were mountains of the stuff on remote islands off Peru, the discovery inspired a guano rush; by the eighteen-fifties, Britain was importing four hundred million pounds of bird poop a year, and the United States a hundred and seventy million pounds. In 1856, the U.S. Congress passed the Guano Islands Act, which authorized Americans to lay claim to any deserted guano islands they could find. (Through the act, the U.S. did not come into much nitrogen; it did, however, acquire a host of minor territories, including Midway Island.)
By Haber’s day, the appetite for crop-friendly nitrogen was so huge that scientists had turned their attention skyward. Nitrogen is the most common element in the earth’s atmosphere-nearly four times more plentiful than oxygen and more than eighty times more plentiful than argon-but almost all of it is floating around in the intractable form of N2. When the humiliated Haber showed how to bust up N2 to produce ammonia-NH3-he basically solved the problem. No more guano would be needed. Haber had, it was said, figured out how to turn air into bread.
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