Ask A Scientist© Environmental Science Archive

Author:      scott tiefel
I once heard that cow burps have a considerable effect upon Earth, causing the 
greenhouse effect.  How is this possible?

Response #:  1 of 1
Author:      mortis
This story probably refers to a humorous exhibit in the Environmental Defense 
Fund's traveling show about the Greenhouse effect.  The exhibit shows a 
drawing of a cow's digestive tract and every so often it lights up and the 
sound of a cow burping comes over a loudspeaker.  It is funny but has a 
serious message - every cow has bacteria in its gut that help digest the cow's
food, but also produce a gas called methane in the process.  Methane is called 
a "greenhouse gas" because it traps heat in the atmosphere like carbon-
dioxide.  So if you add up hundreds of burps from millions of cows, you get a 
lot of methane going into the atmosphere, which is just one of many sources of 
air pollution.  Cow burps are a very small part of the over-all problem, 
though.  The carbon-dioxide from burning fossil fuels like coal, oil, and gas 
is a much larger source of greenhouse gas.