Why do cows burp so much methane? Simple answer, 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 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 burping.
An average cow is thought to emit between 542 litres (if located in a barn) and 600 litres (if in a field) of methane per day through burping so its quite a lot!
Burped methane is pretty hard to collect. Can you imagine trying to catch the burps of a whole field of cows? Some farmers already collect the methane given off by fermenting cow manure and use it to generate electricity. The procedure is relatively simple: manure is stored in huge tanks — anaerobic digesters — which are deprived of oxygen and kept at temperatures of 100F. 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.
Instead of trying to contain the gas, other scientists are trying to develop a vaccine that will stop the methane being produced.