Harvesting the Air

Published: 21st January 2016 12:00 AM  |   Last Updated: 20th January 2016 01:29 PM   |  A+A-


Two German scientists, Fritz Haber and Carl Bosch, devised chlorine gas weapons that were used against French and British troops, in the First World War. Haber’s first wife committed suicide. Then they went on to invent new forms of explosives. During the Second World War, they worked for Hitler, developing a coal based substitute for petroleum that fuelled Nazi planes and trucks. Without the Haber-Bosch process Germany may have been rendered powerless two years earlier in the First World War. Without it, neither Hitler nor the Nazis may have become powerful!

I had never heard of Haber or Bosch until 2012. I suspect you, the reader, are reading about them for the first time.

To me, these two men are perhaps the greatest scientific heroes of the twentieth century – rivalling Edison and Ford and Fleming and Borlaug and Einstein.

Why would anyone admire Nazi bomb makers?

In 1900, the world had two billion people. In 2013, it has seven billion. How did this population explosion happen? Why has there been no famine due to food shortage in the last few decades? In fact there is an epidemic of obesity! Would you believe the answer?  Haber and Bosch!

Most famines in the last hundred years have been because of wars, lack of access or poor administration. Food deficit has NOT been an issue.

The Bengal famine during World war 2 and a Dhathu Varsha famine of the nineteenth century happened when the world population was much smaller. Historians blame British callousness for both. But famines are far older than colonialism. The Mahabharatha has a story of mongoose that arrives at Yudhistra’s Rajasuya yajna, and narrates how it became golden during a famine. Chandragupta Maurya abdicated his throne and became an ascetic as he could not feed his people during a famine. The Irish potato famine happened in the middle of the nineteenth century.

Jared Diamond, in his book Guns Germs and Steel, states that 80% of the food humans eat, by weight, comes from only 12 species of plants – rice, wheat, corn, barley, sorghum, soybean, manioc, potato, sweet potato, sugarcane, sugar-beet and banana. They need the right soil and water, but also a vital fertilizing element – nitrogen. The Earth’s atmosphere is 80% nitrogen, but in this form, most crop plants cannot use it. They need something called fixed nitrogen, which is produced by lightning, natural nitrates in the soil, animal dung, decaying plant material and certain legumes.

Crucially, the amount of fixed nitrogen available by these natural processes limits the amount of food crops humans can grow, regardless of the land and water available. In the 19th century, this problem was circumvented first, by expanding the area of land under cultivation – the great prairies of North America - and second, by utilizing mountains of guano (bat and bird dung) and saltpeter discovered in South America. Europe imported guano from South America like they imported spices and clothes from India, silk and tea from China and slaves from Africa – in ship loads.

In the twentieth century, these South American supplies of fertilizer ran out. So, nitrogen shortage threatened food supply; unless somebody discovered a way to manufacture artificial fertilizer, using the nitrogen in the atmosphere. This is exactly what Haber and Bosch did. They invented the Haber-Bosch process, ammonia fertilizers, massive factories that would produce them in vast quantities.

Nature breaks apart a nitrogen molecule at high temperature and combines it with hydrogen to produce ammonia. The only natural force with the adequate energy for this is lightning. Haber, collaborating with Robert Le Rossignol, discovered a way to break apart nitrogen at high pressures but somewhat lower temperatures and turn it into ammonia. This was not a single Eureka breakthrough. They ran a series of experiments making a number of gradual improvements until they produced ammonia at high pressures and low temperatures. The German chemical company BASF,a pioneer of the chemical industry, bought Haber’s patents. BASF became an industrial giant by synthesizing artificial dyes like aniline, a rival to indigo, one of India’s most valuable exports.

At BASF, Haber discovered a process, using osmium as a catalyst, which produced ammonia in large volumes. But to produced ammonia on an industrial scale they needed very high pressures. One hundred atmospheres was Haber’s estimate of the pressure required. BASF thought this was impossible; cylinders had exploded even at seven atmospheres of pressure. But BASF had a scientist Carl Bosch, who specialized in metallurgy. And he believed they could produce industrial scale machines. Heinrich von Brunck, head of BASF, decided to gamble on Haber’s mechanism and Bosch’s expertise in metals to build the factories.

They won Nobel prizes for this – Haber in 1920 and Bosch in 1932. France hunted for Haber as a war criminal for using cholrine against them in WW1. But after he was awarded the Nobel, France gave up the hunt. For the next decade, France and England used their armies to try to steal the industrial secret that the Haber-Bosch process was; but it was too complex to be copied or stolen and too vital to be destroyed. The great fear was that it not only produced ammonia fertilizer, but also explosives for Hitler’s army.

Haber, born a Jew, converted to Christianity, but ironically, this did not help him avoid the wrath and hatred of the Nazis. He fled Germany for Switzerland and died there; ironically, though his invention allowed Adolf Hitler to make Germany militarily powerful and independent, it was inadequate to overcome his hatred for Jews or tolerate Haber.

Today all artificial nitrogen fertilizer is produced by the Haber-Bosch process. Four billion people owe their existence to their invention, but are ignorant that such men lived and what they gave the world. This invention triggered of the first of several Green Revolutions, the most famous and most recent of which was the work of Norman Borlaug.

I first read about them in a book called “The Alchemy of Air”, by Thomas Hager. Another researcher of engineering history, Vaclav Smil, justly calls their invention the most crucial one of the twentieth century.


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