Comment by adrian_b
2 days ago
Currently hydrogen made from natural gas is the cheapest, but the Haber process could equally well use hydrogen made from water electrolysis using solar/wind energy.
In that case there will be no production of CO2.
The only reason why this is not done yet is because avoiding the production of CO2 would raise the cost of ammonia, then the costs of fertilizers and various other chemical substances, including explosives, which would trigger a cascade of price increases in food and in many other products.
> but the Haber process could equally well use hydrogen made from water electrolysis using solar/wind energy.
You can also use methane pyrolysis, which outputs solid carbon instead of CO2. It's supposed to be somewhere in the middle of cost between steam methane reforming and water electrolysis.