Well, they are almost the same.

Methane is being collected from landfills and sewage treatment plants now as a fuel source. Quite a few sewage treatment plants burn collected methane for heat and/or to generate electricity.

I don't see why compressed methane wouldn't work in a Civic GX, as an example.

Recovering methane from landfills, farm wastes, and sewage treatment plants would not only provide fuel, but would also, as you have identified, reduce the release of a potent greenhouse gas.

Harry