One of the great, unheralded innovations of the 20th century has been the creation of mass-produced fertilizer. Known as the Haber-Bosch ammonia synthesis process, this discovery created abundant fertilizer that was used to fortify harvests around the world, thus preventing starvation.

But the synthesis of ammonia involves the creation of excess amounts of carbon dioxide — a major greenhouse gas. In fact, an estimated 1.4% of global carbon dioxide emissions are the result of ammonia production.

Now, Paul Chirik, the Edwards S. Sanford Professor of Chemistry at Princeton University, and his colleagues have published a paper that outlines a way to produce fertilizer through carbon-free ammonia synthesis.

The researchers found that the formation of weak element-hydrogen chemical bonds can be created by shining blue light on iridium. This process involves no massive outlays of energy and is achieved without creating a carbon byproduct.

“The big breakthrough here is being able to take light and then promote a chemical reaction to make a bond that’s really weak, that you couldn’t do without an external stimulus,” said Chirik. “In the past, that stimulus has been coupled with making waste or consumption of electricity. Here, we’re doing it with light.”

This work could be the key to ending world food scarcity in a carbon-neutral way.