The debate rages back and forth about whether cars or cattle are worse for the environment. As a global warming agent, methane is 23 times more powerful than carbon dioxide, and bovines pump the stuff out by the pantsful โ€” estimates arrage around 26-132 gallons per cow, per day. There are 1.5 billion of the animals in the world today, and it's estimated that agricultural methane production could increase 60% by 2030. [Howstuffworks]