It's a bit of a stretch to call Gold a "respected" astronomer. He had a long history of dubious theories even before "The Deep Hot Biosphere". The small handful of ideas which were sort of vindicated get all the publicity, but there were hordes of ridiculous misses for every supposed hit.

Regardless, getting back to the original topic there's a lot of methane in outer space and it's certainly not biogenic. For example, Titan has lots of methane. I can't see any plausible scenario for importing hydrocarbons to Earth, though. It makes more sense to use solar energy to create biodiesel or maybe even hydrogen fuel.