"Collectively the world's livestock produce 10 percent of all greenhouse
gases, including 25 percent of the methane, among the most potent of
them all. Then there is water... It takes 500 liters to raise a kilo
of potatoes; 900 for a kilo of wheat; nearly 2000 for rice; 3500 for
a kilo of chicken; and a staggering 100,000 liters for a kilo of beef."
Source: NewScientist magazine; March 13, 2004