Fixing nitrogen fixing

In the early 20th century the newly developed Haber–Bosch process transformed food production. Reliable access to ammonia-based fertilisers was a huge boost to agriculture and helped to sustain the planet’s rapidly growing population. Today, giant Haber–Bosch reactors produce around 180 million tonnes of ammonia each year, using up more than 1% of the total energy produced world-wide. The process is also intertwined with fossil fuel extraction – the hydrogen feedstocks are made by steam reformation of coal and natural gas – and is directly responsible for 450 million tonnes of carbon dioxide emissions annually.

With the urgent need to cut society’s carbon emissions, Haber–Bosch is long overdue a makeover. Many researchers now believe that sustainably produced ‘green’ ammonia would not only reduce the environmental impact of fertilisers, but could also be used as a clean energy carrier.