Methane is a horrible greenhouse gas. CO2 is a bad one. So removing methane and getting CO2 is a good thing.
However if you start actively producing methane for use in something like this, then the greenhouse benefits are negative.
However if you start actively producing methane for use in something like this, then the greenhouse benefits are negative.
As I like to point out in every HN post on Bloom Energy, these may be fuel cells, but they're still burning fossil fuels.