Energy Saver News; WattBusters - Cow Flatulence

Air quality and global warming are dynamic environmental and political issues that are often aimed at large, industrial businesses but here's a different take on the subject. Some studies show that cow gas emanating from either end of the cow may have a profound affect on the atmosphere. The gas in question is methane.

Bacteria in the stomachs of cows break down and ferment fodder during digestion, producing methane. The 'southern' end of the cow creates manure and we can collect the methane it gives off as it ferments for use in generating electricity. The procedure is relatively simple: manure is stored in huge tanks - anaerobic digesters - which are deprived of oxygen and kept at temperatures of 100°F, much like the stomach of a cow. The conditions are designed to let anaerobic bacteria thrive and do the work of breaking the manure down. The large volume of "biogas" released - which contains about 90% methane - is piped to an engine which burns the gas and uses the heat energy to generate electricity. The leftover manure is compressed; fluid is drained away and used as fertilizer; and the solids are dried out and used as bedding for the herd and compost.

While manure-derived methane is proving very useful, the methane cows burp is causing problems. Methane is a greenhouse gas and, in the atmosphere, contributes to global warming. Cows burp an abundant supply of it every day - about 280 liters per animal (in other words, the average cow could fill 140 two-liter soda bottles with gas daily). Unfortunately, burped methane is more difficult to collect, with the result that about six million metric tons of it float blissfully up into the atmosphere every year. And that's just from herds in the United States. (Worldwide, ruminant livestock - including cattle, sheep, goats, and buffalo - produce about 80 million metric tons of methane per year, accounting for 22% of human-induced methane emissions.)

Methane is second only to carbon dioxide in the list of greenhouse gases. According to the Intergovernmental Panel on Climate Change, it's 21 times better at trapping heat in the atmosphere than CO2 (a fact that can be attributed to the larger size of the methane molecule - CH4). The six million tons of methane that North American cows burp annually are equivalent to 36 million tons of carbon dioxide.

Why do cows burp so much methane? As with the anaerobic digester, the answer lies with bacteria. Billions of bacteria are busy at work in the cow's rumen (the first of the four chambers in its stomach), breaking down grass and hay in a process known as enteric fermentation. The bacteria - which live symbiotically in the cow's gut - are essential to its digestive process. One of the anaerobic bacteria produces large quantities of methane as a byproduct, which the cow gets rid of by flatulence and burping.

Diet is also one of the reasons cows are so 'explosive'. Beef cattle were originally designed to eat grass but now most beef live on feed mixtures. The reason? It's faster, and so more profitable. Although the cows get very big, very fast, the enormous quantities of corn, protein supplements, antibiotics and other drugs, including growth hormones create gas. Petroleum fertilizer is used to grow much of the corn used in feed, and in effect, we have basically created a tasty, oil-fueled, gas-producing machine.

The next time you factor in some of the possible causes of global warming, you may see a 1/4 pound burger staring back at you from your grill. (Authors note: I eat burgers but now look at them in a much different light.)