Correct me if i'm wrong, but I think all humans produce methane, vegetarian or not. But the pollution is negligible. It's not as if you fart every hour, right?

could it be they are full of s#@t?

No. Cows are not vegetarians in the way that humans can be, they are ruminants. They have a specially-equipped stomach for processing grass, which humans are unable to eat. Cows have a rumen which is filled with anaerobic organisms that assist them in the digestion of cellulose. This fermentation process breaks down the grass that they eat. The byproduct of this process is methane, which the cow expells at a rate of about 600 liters per day. Humans don't eat grass because we are unable to digest cellulose (we don't have a rumen). We can eat grains and vegetables, but the ones we eat are much easier for us to digest. Any byproduct of our digestion process is negligible compared to that of a cow, as we only have one stomach and not nearly so much fermentation happening in it.

Two different digestive systems. Cows have several stomachs and chew a cud and produce LOTS of methane no matter what they eat. It is part of their digestive system to expel gas. Not us. If WE have a lot of gas it means we are not digesting our food very well that it is fermenting when it shouldn't be.

How come bovines cause global warming now? Why didn't they do it years ago? I know there are more bovines now but wasn't USA full of buffalo and bison in the early nineteenth century?

No. Humans and cows are two different species of animals. Cows are ruminant animals and as part of their natural digestive system, they produce methane. They chew the cud. They have a second stomach and inside that stomach there's bacteria that breaks down cellulose in grass to release energy. The process is an anaerobic process so it's in the absence of oxygen and this process causes the release of methane, mostly through belching. Humans do not digest foods via this process and hence do not produce any significant amount of methane. However the humans that eats meat is directly responsible for the existence of such unprecedentedly and unnaturally huge numbers of animals (ie, livestock animals) on the face of the planet. Taking into account of the entire meat cycle, from the deforestation to open up grazing lands to the slaughter, refrigeration onsite, refrigeration during transportation. refrigeration on supermarket shelves, refrigeration continue after the purchase at home etc, therefore it is a proven scientitic fact that a vegetarian diet would leave a far far smaller carbon foot print than that of a typical meat-eater. Did you know that the livestock industry pumps out more greenhouse gases than cars, trucks, trains, airplanes, ships and all other forms of transportations combined? - [2006 UN Report warning.] Even Al Gore's Inconvenient Truth failed to mention that consuming meat and dairy is worse for the environment than all emissions from the automotive industry. Did you also know that even though most people in the field knows how extremely energy intensive it is to produce alumininium by electrolysis, 1 pound of beef, however, requires FOUR TIMES the amount of energy needed to produce 1 pound of aluminium. Furthermore, ➊ Factory farms produce massive amounts of dust and other contamination that pollutes our air. A study in Texas found that animal feedlots in the state produce more than 14 million pounds of particulate dust every year and that the dust 'contains biologically active organisms such as bacteria, mold, and fungi from the feces and the feed. ➋ According to the nonprofit group Greenpeace, all the wild animals and trees in more than 2.9 million acres of rainforest were destroyed in the 2004-2005 crop season in order to grow crops that are used to feed chickens and other animals in factory farms. ➌ According to a 2006 UN report, the livestock sector causes more greenhouse gases worldwide than the entire transportation sector. ➍ Nitrous oxide is about 300 times more potent as a global warming gas than carbon dioxide. According to the U.N., the meat, egg, and dairy industries account for a staggering 65 percent of worldwide nitrous oxide emissions. ➎ According to the Environmental Protection Agency, the run-off from factory farms pollutes our waterways more than all other industrial sources combined. The EPA reports that chicken, hog, and cattle excrement have polluted 35,000 miles of rivers in 22 states and contaminated groundwater in 17 states. ➏ It takes 16 pounds of grain and 2,500 gallons of water to produce 1 pound of meat. One average meat eater could consume that pound of meat during a meal, while 16 people could have been fed on the grain it takes to produce that pound of meat. ➐ The meat industry causes more water pollution in the US than all other industries combined because the animals raised for food produce 130 times more excrement than the entire human population--86,000 lbs per second. A typical pig factory farm generates a quantity of raw waste equal to that of a city of 12,000 people. ➑ Every 2 seconds, a child starves to death somewhere in the world. Countries such as Ethiopia and some Central American countries use their farmland to supply the United States with cheap burgers instead of growing healthful grain foods for their own starving people. ➒ The livestock population of the US consumes enough grain and soybeans to feed more than 5 times its human population. 90% of all corn and 80% of all grains and beans grown in the US are used to feed livestock animals. ➓ 75 percent of U.S topsoil has been lost to date, 85 percent of that loss is due to livestock rearing. Meat is murder on the environment A kilogram of beef is responsible for more greenhouse gas emissions and other pollution than driving for 3 hours while leaving all the lights on back home. What makes meat-eating and hence the livestock industry as a whole an urgent threat to global warming is that it is the single biggest net producer of man made methane and the gas is 72 times more potent as a global warming gas than CO2 (calculated over a 20 year period). Every ton of methane released into the atmosphere is equivalent to 72 tons of CO2. If you think it can't get any worse, think again. There is a massive deposit of frozen methane at the bottom of the ocean in the form of methane hydrate. The amount locked in place is more than all the methane you could get from fossil fuel. http://suprememastertv.com/bbs/board.php?bo_table=sos&sca=sos_1&wr_id=509 If the continuing practice of pumping out man made methanes at a rate like the livestock industry is, and which is also on the rise to supply the growing demands of meat-eaters, the ocean will eventually get warm enough to trigger a sudden release of all those frozen methane into the atmosphere. Remember, methane is 72 times more warming than CO2 (over a 20 year period) and hence once that point is reached and all the methane from the ocean is suddenly released, global warming will get a massive steroid boost. Already, a range of studies have found that Arctic sea ice is melting faster. The ice in the artic keeps the ocean cold and at the same time reflects about 80% of the sun's heat, thus stabilizing that colder temperature of the ocean, which in turn keeps the frozen methane locked in place. The picture is very grim but if everyone switches to a vegetarian diet, there is still hope.

And tie that in to the fact that vegetarians are eating the cows' food. Does that mean that they're gonna let the cows starve to death?