Natural Gas? Cows Toot Out Most Methane By Becky Oskin A new snapshot of U.S. methane emissions in 2004 shows livestock — primarily cattle and pigs — were the country’s worst gas emitters at the time. The study also found that livestock expelled 40 percent more methane than had been estimated by … Continue reading ‘Real Natural Gas’ From Cows and Pigs Increases Atmospheric Methane Much More Than Previously Understood