Fritz Haber

By Julien Moreau

Fritz Haber was born December 9, 1868, in Breslau, in the Kingdom of Prussia, and his invention feeds roughly half of humanity. The problem he solved was the oldest in agriculture: nitrogen. Plants need it to grow, the air is four-fifths nitrogen, but atmospheric nitrogen is chemically inert — useless to crops. By 1900 the world was running out of natural fertilizer: Chilean saltpeter and guano could not feed a growing population, and chemists warned of mass starvation within decades.

Haber's answer was to force nitrogen and hydrogen to combine under brutal conditions — hundreds of atmospheres of pressure, hundreds of degrees, over an iron catalyst — producing ammonia, which can be turned into fertilizer. The chemistry was known to be theoretically possible; everyone considered it practically impossible. Working at Karlsruhe in 1909, Haber and his assistant Robert Le Rossignol built a tabletop apparatus that produced ammonia drop by drop, proving the reaction could be driven. Carl Bosch at BASF then did the industrial miracle: scaling a laboratory trick to giant steel reactors that could survive the pressure and heat, solving hundreds of engineering problems along the way. The first commercial plant at Oppau began producing in 1913.

Haber's legacy is split in two. The ammonia synthesis won him the 1918 Nobel Prize in Chemistry and underwrites the Green Revolution — without synthetic fertilizer, the earth could feed perhaps half its current population. But Haber was also a fervent German patriot who in World War I directed the Kaiser Wilhelm Institute toward chemical warfare, personally supervising the first chlorine gas attack at Ypres in April 1915. His wife, the chemist Clara Immerwahr, killed herself days later in protest. Jewish by birth, Haber was driven from Germany by the Nazis in 1933 despite his war service; he died January 29, 1934, in Basel, Switzerland — the man who fed the world and poisoned its battlefields.

Haber's breakthrough was measured in drops. In the summer of 1909, the tabletop apparatus at Karlsruhe — built with the English assistant Robert Le Rossignol — produced ammonia at five grams per hour, barely a thimbleful, but it proved the thermodynamic point: with enough pressure and the right catalyst, nitrogen would yield. Carl Bosch's scale-up at BASF was the greater engineering feat: pressures of 200 atmospheres at 500 degrees demanded steels that did not exist, hydrogen that embrittled everything it touched, and catalysts by the ton. The Oppau plant, opening in September 1913, was the largest chemical engineering project of its age. Haber's war record is documented without mercy: as head of the Kaiser Wilhelm Institute's chemistry section, he organized the chlorine release at Ypres on April 22, 1915 — 168 tons of gas, 5,000 Allied casualties — and was promoted to captain the next day. His wife Clara, herself a PhD chemist, shot herself with his service pistol on May 2; Haber left the next morning for the Eastern Front. Awarded the 1918 Nobel Prize in Chemistry (presented in 1919), he spent the Weimar years trying to extract gold from seawater to pay reparations — a magnificent failure. The Nazis' 1933 civil-service law expelled him despite his Iron Cross; he died in a Basel hotel on January 29, 1934, en route to a post in Palestine.

Impact on civilization

Synthetic fertilizer is the most consequential chemical process in human history after fire. Before Haber-Bosch, the food supply was capped by the nitrogen the soil could fix naturally; famine was a structural feature of civilization. After it, crop yields multiplied — the same acre could feed several times more people — and the twentieth century's population explosion, from under two billion to eight billion, became physically possible. Roughly half the nitrogen atoms in your body right now passed through a Haber-Bosch reactor. The process also underwrote the munitions of two world wars, since ammonia is the feedstock for nitric acid and explosives — the same molecule that grows wheat can fill a shell. No invention better illustrates the double edge of chemistry: Haber's process is why humanity did not starve, and a reminder that every tool of abundance is also a tool of power.

The nitrogen cycle itself now bears humanity's fingerprint: synthetic fertilizer has doubled the planet's reactive nitrogen, greening farms and choking waterways with algal blooms in equal measure. Haber's process is the reason eight billion people eat — and one of the reasons the Anthropocene looks the way it does.