The hydrogen is combined with atmospheric nitrogen to produce ammonia. Usually we source it from natural gas, so all our fertilizer is incredibly carbon intensive to make whereas this would at least be carbon neutral.

At the end, you'd just oxidize the CO back to CO2 before release, like a catalytic converter does, or use the CO as a chemical building block to produce hydrocarbons.

I assume he meant carbon sequestration.

Yes, my prose was a bit less clear than I had intended. You can oxidize the CO and be carbon neutral or sequester it and be carbon negative.