A cow produces 60 kilos per head per year of methane gas. Normal tillage farming, (growing cereals, soy beans etc.) releases carbon into the atmosphere at about 3 tons per hectare. Switching to grass (to graze cattle say) sequesters another 750 kg per year. So you get a net gain of 3,750 kgs of carbon sequestered (or kept in the soil and out of the atmosphere) by switching to cattle grazing.

This seems to more than makes up for the 60 kilos of methane produced per head of cattle. Multiplying 60 kilos of methane times 25 (methane they say is worse than carbon for the atmosphere) yeilds 1,500 kg of green house gas (per hectare assuming 1 hd per hectare).

Subtract that from the carbon sequesterd from grazing and you still get a 2,250 kg of green house gas taken out of the atmosphere by switching from tillage farming to cattle grazing. Also it usually takes a lot more than a hectare of grass pasture per head to grow cattle.

http://www.swcc.cn/waswc/articles/Soil Conservation and the Kyoto Protocol Facts and Figures-new.htm#Global

So finally we can eat a big T bone and not feel guilty! That is what the numbers say anyway. Eat grass fed beef and help save the World from global warming!!!