Well, methane is a useful fuel source, but the engineering costs of piping it about around is what makes it uneconomical, and underused, or wasted by flaming it off. One use for it is being fed to methane using bacteria to produce single-cell protein for animal feed. That application doesn't address the carbon footprint at all, but it just goes to show ... we could use methane, but we don't, because it costs too much, to use, from an engineering standpoint. I'm sure there's pilot plants that use methane, or even local uses that are very important to the local economy, but its not universal, because the engineering costs just reduce viability.
Note: you haven't addressed a fundamental. You've picked an underused fuel source, and decided to offset carbon dioxide emission by simply wasting some, to produce more inert material -- carbon, that you now have to dispose of. Just because carbon is fairly nonreactive, doesn't mean that a municipality wants it lying around, or buried. The rules are the same, garbage is garbage, and you have to pay. I'd bet anything, if you produced 10 million metric tons of gem quality diamonds in a big heap, once every passerby grabbed a handful to make jewelry, some pencil pusher will show up and say, "You going to take care of this eye-sore?"
Furthermore, the more fuel you use, and find an application for, if its a profitable app, then the more demand there is. And that results in more consumption, to release more greenhouse gasses. I suppose, there's the benefit of reducing methane release (itself a greenhouse gas), and sparing other fossil fuel use. But look at it this way. You're putting a great deal of effort, for a moderate benefit. You're adding local costs, to benefit the whole world. Engineering is often about constraining the possible chemistry to real world economical limitations. You seem to be ignoring that.