Originally Posted by Quicksilver

What about cows???

It has been estimated that 9 to 12% of the energy that a cow consumes is turned to methane that is released either through flatulence or burping (Radford, 2001). A huge number of factors affect methane emission, including diet, barn conditions and whether the cow is lactating, but an average cow in a barn produce 542 liters of methane a day, and 600 liters when out in a field (Adam, 2000).

These estimates were made using a trace gas (sulphur hexofluoride) that was released at known points within a barn containing 90 cattle. Levels of this trace gas and CO2 are then measured 30 metres downwind of the shed and thus they can estimate how much CO2 is released per cow per day. All this methane can add up to a significant amount. Australia's 140 million sheep and cattle are estimated to produce one seventh of the nation's total greenhouse gas emissions, whilst America's 100 million cattle also are major contributors (Major, 2000).

http://rucus.ru.ac.za/~wolfman/Essays/Cow.html