Cutting Climate Costs of Nitrogen Fertilizer Production

by Emil Morhardt

Nitrogen fertilizer, crucial for growing commercial crops, is based on ammonia made in factories using the energy- and CO2-intensive Haber-Bosch process; hydrogen is stripped off natural gas using steam, then reacted with nitrogen in the air. The process uses repeated cycling at high temperature and pressure, and consumes 2% of the world’s energy production. Stuart Licht and colleagues at George Washington University noticed, however, that a recently developed fuel cell using ammonia as a fuel and producing electricity as an output might be run in reverse: electricity in, ammonia out, with a whole lot less temperature and pressure (and energy) required. Even better, it wouldn’t need natural gas as a hydrogen source—with its attendant CO2 production—being able to get it from air and steam at a temperature lower than a household oven baking bread and at ambient pressure. Furthermore only simple materials would be required; molten sodium and potassium hydroxide (inexpensive commodity chemicals), nickel electrodes, and an iron oxide catalyst, all in a single pot.

After considerable experimentation with different temperatures, voltages, forms of iron oxide, Continue reading