[TigersEye]

The methane comes mainly from the burps; farts are more likely to be hydrogen sulfide.

Errr, is hydrogen sulfide flammable? Because if it isn't I can Google up some strange pics to argue the point with you. ;^)

[Mr. Lucky]

Cattle are ruminants and, as such, produce methane in their digestive process. The methane is expelled as a burp, not a fart. While this simple fact may not be known to the New York Times, it's hardly a secret. Google on something to the effect of "cow burps".

[Old Professer]

Very.

BTW, the smell gives it away, rotten eggs, methane is pretty much odorless.

The natural gas you have in your house averages about 80-85% methane in most of the country and the gas company adds an odorant to allow a leak to be readily detected.

[TigersEye]

US EPA Methane Sources and Emissions
(I was going to post the table on this page but I can't do it.)

Looks like the U.S. is steadily reducing methane emissions. Apparently wetlands are responsible for 76% of all naturally produced methane. Sorry, duck hunters, for the good of the chirren we gotta dredge and drain.