I consider myself a fairly "green" person. Here is why NOT using coal bed methane could actually be worse than the potential carbon footprint.
Methane is a more potent greenhouse gas than methane (about 80 x worse). The coal bed methane, for shallow coal deposits at least, is likely leaking to the surface and escaping anyway. My thought process is capture the methane, burn it to beneficial use, and you are left with CO2 instead of methane.