There's an interesting graph that someone posted in https://aussie.zone/comment/14827931, but I am no expert so I have no idea personally, just sharing that, which seems to suggest that the highest areas are residential energy and road transportation. Whether that in turn traces to Methane I have no idea:-).
The nice thing is that if we could work on either, then we could work on both at the same time. Caveat: we cannot work on either, for the most part, bc people are selfish and short-sighted:-(.