Dude, Earth's atmosphere used to be methane.
How do you know this? Moron. You're such a laughable douchebag.

The scientists show that the atmosphere of Earth just 500 million years after its creation was not a methane-filled wasteland as previously proposed, but instead was much closer to the conditions of our current atmosphere.
https://astrobiology.nasa.gov/news/earths-early-atmosphere-an-update/