This series usually profiles people whose contributions were overwhelmingly good, with complications attached. Haber is here for the opposite reason: no other figure shows so starkly how one mind, one discipline and one patriotism can produce both a vast good and a horror. His case fits the series' criteria (direct, documented, touching billions of lives) and adds a warning.
A note: this piece mentions suicide. If you are struggling, please reach out to a local crisis line or someone you trust.
The problem: plants starve for nitrogen
Plants need nitrogen to grow, and the air is about 78 percent nitrogen. The catch is that atmospheric nitrogen is locked in pairs of atoms bound so tightly that plants can't use it. For all of history, farmers depended on the slow natural processes that "fix" nitrogen into usable forms: manure, crop rotation with beans and clover, and, by the 1800s, imported mineral deposits such as Chilean saltpetre and seabird guano. By 1900, scientists were warning that these supplies could not feed a growing world.
The breakthrough
Haber, a chemist born in 1868 in Breslau (now Wrocław, Poland), worked on the problem at Karlsruhe with his British assistant, Robert Le Rossignol, born in Jersey. In 1909 they showed that nitrogen and hydrogen could be forced to combine into ammonia at high temperature and enormous pressure, over a catalyst. It was a tabletop machine dripping a little ammonia, but it proved it could be done.
The chemical company BASF bought the idea, and its engineer Carl Bosch solved the brutal practical problems: steel vessels that could survive the pressures, a cheap catalyst to replace the rare metals Haber had used, and a steady supply of pure hydrogen. The first industrial plant opened at Oppau in 1913. Haber won the Nobel Prize in Chemistry for 1918; Bosch shared one in 1931.
Haber's process turned the sky into fertiliser. Without it, about half the people alive today probably could not be fed.
How many people does it feed?
Estimates by researchers led by Jan Willem Erisman, published in 2008, suggest that synthetic nitrogen fertiliser supported about 48 percent of the world's population that year. At today's population, that would be roughly four billion people, though it's an extrapolation, and separating fertiliser's contribution from better seeds, irrigation and machinery is genuinely hard. (Norman Borlaug's high-yield wheat, profiled in this series, only worked so well because it could absorb this fertiliser.)
The process is now among the largest industrial activities on Earth: around 230 million tonnes of ammonia a year in 2018, consuming roughly 1–2 percent of the world's energy and producing about 3 percent of global carbon-dioxide emissions.
The other half of the story
Ammonia doesn't only make fertiliser. It makes nitric acid, and nitric acid makes explosives. When the First World War began in 1914, Britain's naval blockade cut Germany off from Chilean saltpetre, which it needed for munitions. The new Haber–Bosch plants filled the gap. Many historians believe Germany would have run out of explosives and lost the war much sooner without them.
Haber went further. A fervent German patriot, he threw himself into developing chemical weapons and led the work personally. On 22 April 1915, near Ypres in Belgium, German troops opened thousands of cylinders and released about 170 tonnes of chlorine on the wind toward French lines. The gas tore a gap several kilometres wide in the front. Estimates of French deaths from the gas alone run from about 800 to 1,400. Germany argued that the 1899 Hague Declaration banned gas shells, not gas released from cylinders. The Allies called it a flagrant breach of international law, and soon used gas themselves.
By the war's end, poison gas had caused roughly 1.3 million casualties and about 90,000 deaths, by commonly cited estimates. Haber reportedly said that in peacetime a scientist belongs to the world, but in wartime to his country.
The personal cost
His wife, Clara Immerwahr, was a gifted chemist, the first woman to earn a doctorate at the University of Breslau. On 2 May 1915, days after Ypres, she shot herself with his service pistol. Her reasons were never recorded clearly; her opposition to his weapons work is often given as the cause, but historians still debate it. The next morning Haber left to direct gas attacks on the Eastern Front.
After the war, scientists at his institute developed Zyklon fumigants for pest control. A later version, Zyklon B, was used by the Nazis to murder people in gas chambers, though historians say Haber had no direct part in that version. Haber, born Jewish and a convert to Christianity, was forced out of his post by Nazi laws in 1933. He died in January 1934 in Basel, Switzerland, travelling toward a new post in what is now Israel. Several members of his extended family were later killed in Nazi camps.
The honest complications, all of them
- Credit is shared. Haber proved the chemistry; Bosch and BASF's engineers made it work at scale. The process carries both names for good reason.
- The good is not clean either. Excess fertiliser washes into rivers and seas, causing algal blooms and oxygen-starved "dead zones," and nitrogen pollution and emissions are serious environmental problems.
- The bad is not only his. Every major power in the war adopted gas. Haber's role was leading, not unique.
- You can't net them out. There is no honest way to subtract 90,000 gas deaths from billions fed, and this piece doesn't try. Both are true, and both belong to the same man.
Honorable mentions
- Carl Bosch, who turned Haber's experiment into an industry.
- Robert Le Rossignol, Haber's co-inventor at Karlsruhe, often left out of the story.
- Clara Immerwahr, a pioneering scientist remembered today by an award in her name for women in chemistry.
- William Crookes, who warned in 1898 that the world would face a nitrogen famine unless chemists found a way to fix nitrogen from the air.
The takeaway
Fritz Haber showed in 1909 how to turn the air's nitrogen into ammonia, and with Carl Bosch's engineering the Haber–Bosch process now underpins fertiliser that feeds, by careful estimates, around half of humanity. The same chemistry supplied Germany's explosives in the First World War, and Haber himself led the first mass chlorine-gas attack at Ypres in 1915. His life is the clearest case in history that a scientific gift carries no moral direction of its own; the direction comes from the people who use it.
Try this: next time you see a field of bright green crops, remember that much of the nitrogen in them was taken from the air by a 1909 invention. Then ask the Haber question about a technology you use or work on: what is the best and the worst thing it could be used for?
Sources & Further Reading
Sources
- Haber's biography: born 1868 in Breslau; ammonia synthesis with Robert Le Rossignol at Karlsruhe (1909); 1918 Nobel Prize; chemical-weapons leadership; resignation in 1933; death in Basel, 29 January 1934.
- Carl Bosch's scale-up at BASF; first industrial plant at Oppau (1913); his 1931 Nobel Prize (shared with Friedrich Bergius).
- Erisman et al., "How a century of ammonia synthesis changed the world," Nature Geoscience (2008); Our World in Data, "How many people does synthetic fertilizer feed?" (44% in 2000, 48% in 2008; extrapolation to today).
- Ammonia output (about 230 million tonnes in 2018), energy use (1–2% of global energy) and emissions (about 3% of global CO₂): standard industry and energy references.
- Second Battle of Ypres, 22 April 1915: about 168 long tons (171 tonnes) of chlorine; French gas deaths estimated at 800–1,400; Hague Declaration of 1899 dispute.
- WWI gas totals: about 1.3 million casualties and 90,000 deaths (commonly cited; historian L. F. Haber, his son, thought them possibly too high).
- Clara Immerwahr: first woman PhD at Breslau (1900); death on 2 May 1915; debated motives.
- Zyklon development at Haber's institute and his lack of direct involvement in Zyklon B.
Go deeper
- 📘 Enriching the Earth — Vaclav Smil (the definitive history of nitrogen fixation and its role in feeding the world)
- 📘 The Alchemy of Air — Thomas Hager (a gripping narrative of Haber, Bosch and the process)
- 🌐 Our World in Data — How many people does synthetic fertilizer feed?
- 🌐 Companion piece in this series: Norman Borlaug: The Man Who Fed a Billion People