That's actually pretty darn cool. And sounds like it's a "kit" that could be added to any car. I could have a Fart-stang GT! Or would it be a Must-stain GT?
Actually, a human wastewater treatment plant using/selling methane is just plain smart.
Methane is a worse greenhouse gas than CO2, if that religion matters to you. If so, burning the methane to make 'lectricity ( to power the plant, mostly ) reduces the Methane released. ( I won't tell them about the water vapor, if you don't )
Having a dual fuel car that can run on methane has it's problems, such as the extra mass and reduction in payload, but it does work if you are willing to pay for it, and the new technology is not the methane burning, it's the electronic package that turns the valves for you.