[mbag]

From what I understood, they were using methane in internal combustion engines, so they are not releasing methane into atmosphere, rather burning it and producing CO2. I would assume that some of the methane is going to end up in atmosphere (engine efficiency, leaking from gas tank), but compare that to untreated pig manure, which would produce said methane anyhow.

[mirimir]

Well, we're probably talking about industrial-scale pig farming here. So yes, the carbon in that manure would otherwise likely end up as atmospheric methane. If you applied it sparingly to the soil, much of the carbon would get incorporated into humus. But large pig farms don't have enough land, so they spread thick, and you get methane.

Another issue is that most of the carbon in that manure comes from feed corn. And most of the energy in feed corn comes from ammonia fertilizer, which is made from fossil methane. But hey, it's still a win compared to field spreading.

Right.