A brief history of nitrogen fertiliser

Since the Second World War, synthetic fertilisers, especially those made from ammonia, have played a major role in agriculture on almost all farms except those using organic methods. These have driven a dramatic increase in production through higher yields, but that has come at a high environmental cost in terms of greenhouse gas emissions, air pollution from ammonia, water pollution from high levels of nitrate and biodiversity decline in terms of delicate wild flowers and plants outcompeted by ranker vegetation better able to ulitise nitrogen.

Today, the UK uses just over one million tonnes of nitrogen every year, in over three million tonnes of nitrogen fertiliser, with different products containing different proportions of nitrogen. Ammonia is produced by the Haber-Bosch process – named after German scientists Fritz Haber and Carl Bosch who developed a method to produce synthetic ammonia in 1911. This process turns the inert nitrogen in the air we breathe into reactive nitrogen, by breaking the triple bond which holds nitrogen atoms together in pairs, then forcing them to combine with hydrogen. This requires a temperature of  500°C, 250 atmospheres of pressure (approximately 120 times the pressure in a typical car tyre) and an iron catalyst.

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