What, for humanity, was the most significant technical innovation of the twentieth century? Was it air travel or space flight, television or computers, or nuclear energy, perhaps? Vaclav Smil (1) argues, and I agree with him, that it was not any of these but the Haber-Bosch process for the synthesis of ammonia. The arithmetic is simple. In 1900, there was virtually no synthetic nitrogen fertiliser, and the world population supported by agriculture then was 1.625 million. Had the process not been developed, only half of the 2000 population could have been fed the generally inadequate diet prevalent in 1900, and only 40 per cent could have enjoyed the current average per capita. Surely no other innovation has enabled so many people to live as nitrogen fertiliser - or had its importance so little understood.
Nitrogen fertiliser is admittedly not an unmixed blessing. Nitrate and nitrous oxide are lost from the soil when it is used, causing algal blooms in coastal waters and damage to stratospheric ozone (2). But nitrate is not a threat to your health, it’s essential to the working of your body’s defence system against bacterial gastroenteritis (2,3).
Thomas M Addiscott is a soil scientist, computer modeller and science writer.
1) Smil, V. (2001) Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production The MIT Press, Cambridge, Massachusetts.
2) Addiscott, T.M. (2005) Nitrate, Agriculture and the Environment CABI Publishing, Wallingford.
3) Benjamin, N (2000) ‘Nitrates in the human diet - good or bad?’ Annales de Zootechnologie 49, 207-216.