To remind people, Haber-Bosch process produces fixed nitrogen in the form of ammonia from hydrogen. In the US, almost all hydrogen is produced from natural gas

To remind people, Haber-Bosch process produces fixed nitrogen in the form of ammonia from hydrogen. In the US, almost all hydrogen is produced from natural gas (not coal), although other fuels are more common in places like China. We used to use hydroelectric power to make hydrogen (using electrolysis) for Haber-Bosch, but gas reforming of methane ended up being much cheaper in the 1950s once that process became invented and widespread.