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By Root 784 0

well aware of the problems that nitrogen limitation posed for humanity. “England and all civilised nations stand in deadly peril of not having enough to eat,” warned William Crookes, a scientist and president of the British Association, in a widely quoted 1898 speech. At issue were predicted declines in harvests following the likely exhaustion of imported Peruvian guano stocks and nitrates stripped from Chilean deserts. (Guano is an excellent fertilizer, being composed of seabird excrement—often tens of meters thick—deposited over many centuries on arid offshore islands.) Human populations were rising rapidly, and fears that human fertility could outpace soil fertility were very real. “As mouths multiply, food resources dwindle,” Crookes went on. “I am constrained to show that our wheat-producing soil is totally unequal to the strain put upon it.”

But Crookes was not Malthus. He knew that there was a way out of what he called this “colossal dilemma.” And that path to plenty lay through science. “It is the chemist who must come to the rescue of the threatened communities,” Crookes insisted. “It is through the laboratory that starvation may ultimately be turned into plenty.”4 If William Crookes’s optimism seems old-fashioned, I suspect this is because if a scientist of his caliber were to make a speech in an area of equivalent concern today, he would likely be shouted down as a techno-fantasist. But the historical lesson is that Crookes was right. His challenge may have seemed impossible at the time, yet it was solved by the application of human ingenuity, and within just ten years after he spoke.

However, the chemists who performed this feat, and were later awarded the Nobel Prize in recognition of their stunning breakthrough, worked not for the King but for the Kaiser. And their work was initially put to the service not of feeding the world, but of producing industrial-scale instruments for mass slaughter in the First World War.

ENTER FRITZ HABER

Fritz Haber and Carl Bosch can claim as dramatic an influence on twentieth-century world history as the likes of Stalin, Churchill, and Gandhi, yet their names are barely remembered and their defining achievement little celebrated by today’s generations—even though we benefit from their inventiveness every time we eat a meal. The chemical technique that bears their names, the Haber-Bosch process, was undoubtedly “the most important technical invention of the twentieth century,” according to the Canadian scholar Vaclav Smil, whose book Enriching the Earth is the definitive biography of nitrogen in the modern world. As Smil relates, the “single most important change affecting the world’s population—its expansion from 1.6 billion people in 1900 to today’s 6 billion—would not have been possible without the synthesis of ammonia” for conversion into artificial fertilizers.5

Haber was not the first chemist by any means to take up Crookes’s challenge. But he was the first to refuse to be defeated by it. The problem should have been easy to solve: All the essential chemistry demanded was for N2 to be combined with hydrogen to form ammonia, or NH3. But the twin bonds between nitrogen atoms in atmospheric dinitrogen are extremely strong, and the high temperatures and pressures needed to break them so extreme as to make the process appear technically unfeasible. In 1904 Haber, a professional chemist from a reasonably well-to-do German–Jewish family in Breslau, began work on the problem of ammonia synthesis. Without an offer of financial support from the German chemicals company Badische Anilin-& Soda-Fabrik (better known by its initials, BASF) to the tune of 6,000 marks a year, Fritz Haber too might have been forced to abandon the quest.

The day the world’s nitrogen cycle changed can be dated very precisely: July 2, 1909, when Fritz Haber—in front of two skeptical BASF representatives—demonstrated the synthesis of ammonia in a pressurized metal tube just 74 cm tall and 13 cm in diameter. His breakthrough had been to discover a catalyst (originally uranium, later switched to a form of