This reminds me of US research that was done during the Cold War about surviving a nuclear winter by producing food products directly from petroleum. It's theoretically possible and you could survive on it as a supplemental source of calories.

I think optimizing farming for space flight is probably better, especially if you have always-on solar power (as you do anywhere near the sun) or nuclear power. Hydrocarbons from asteroids and comets are probably better suited for things like plastics manufacture and petrochemicals, since you would not have biotic oil sources in space.