That's generally where methane comes from today, but in time it may come from captured CO₂, e.g. see https://terraformindustries.com/ https://terraformindustrie

That's generally where methane comes from today, but in time it may come from captured CO₂, e.g. see https://terraformindustries.com/ https://terraformindustries.com/ (disclaimer: I am a minor investor).