The Japanese said they could extract oil from steer manure. Maybe we could rig our sewage treatment plants to extract oil from human turds.
Plants already exist that produce power from methane gas. I once built a miniature replica when I was in high school, for a science project. It does work. Its just not efficient.
You need a vast garbage dump to power that kind of thing. And jokes about New York or San Francisco or Hollywood aside, it's just not a realistic possibility at the current stage of affairs.
You can produce oil from a lot of stuff. The Japanese and Israelis, the usual hi-tech suspects, have had ways for years. But they aren't efficient, and there's no obvious or clear way to make them more efficient.