It is not surprising that many people find it hard to take seriously the claims that methane expelled by cows can be a threat to the planet. It seems more like gross-out humor than serious climate science. Particularly since many people believe that the methane comes out at the end of the digestive tract as in humans. Actually most of this methane is expelled by belching.
According to a recent article in The Christian Science Monitor cows burp about once every 40 seconds. Their digestive processes yield as much as 100 gallons a day of methane and much of it is released through belching. Multiply that by all the cows in the world and you can be begin to see why this has no relationship to toilet humor. Considering that methane is a much more powerful greenhouse gas than carbon dioxide with regard to heat trapping (although it does not last nearly as long in the atmosphere) it is clear that this is very serious business.
To make this subject even more grim cows are not the only type of livestock that burp methane. For example, sheep are also part of this problem. A reporter from a Western Australian radio station discovered that in her part of the world this is particularly true because of the high salinity which results in the sheep eating bush that generates lots of burping.
Kay Balatero recently discussed the issue of belching cows on Gristmill blog and noted that scientists are looking for ways to change the diet of livestock to cut down on the belching. She finds herself doubting the wisdom of this effort:
But I'm somewhat skeptical about this dietary tampering; the idea of manipulating cow diets even further than we already have is a little disconcerting. We've seen corn-fed CAFO [confined animal feeding operations] cows become more susceptible to disease as a direct result of eliminating their natural diet of grass, leading to overuse of antibiotics by the beef industry. Would it be better to leave well enough alone, and simply consume less (sustainably raised) beef?
In theory, the problem could be solved by humans becoming vegans in vast numbers. Who needs billions of livestock if we no longer eat beef or lamb or consume dairy products such as milk, cheese, ice cream, and yogurt. The chance of this happening seems to be zero. If civilization is going down, it hardly seems likely that people would give up such perceived pleasures as eating a choice cut of grilled steak or a juicy hamburger from the barbecue during the descent.