‘Earth factory’ method cooks up clean fertilizer underground.

In the 1980s, well diggers in Mali, West Africa uncovered an unusual geological phenomenon: a well streaming with hydrogen gas, which scientists traced back to chemical reactions between water and rock occurring deep within the Earth. Now, researchers are harnessing our planet’s natural heat and pressure to cook up ammonia for fertilizer—potentially reducing the need for chemical plants powered by fossil fuels.

Ammonia, which is primarily used as a source for nitrogen fertilizer and also being considered for use as a green fuel, is the most widely produced chemical in the world today. Unfortunately, the standard method for making ammonia, known as the Haber-Bosch process, consumes enormous amounts of energy—making it a major source of greenhouse gas emissions. In fact, ammonia production is the chemical industry’s biggest greenhouse gas emitter.