‘What has been the most important technical invention of the twentieth century?’ asks Vaclav Smil in Enriching the Earth. He rejects suggestions like computers and aeroplanes, going on to explain that nothing has been as important as the industrial fixing of nitrogen: ‘the single most important change affecting the world’s population – its expansion from 1.6 billion people in 1900 to today’s six billion – would not have been possible without the synthesis of ammonia.’
