Prof Frank Mitloehner, an air quality scientist from UC Davis in California, has become one of the most ardent defenders of livestock agriculture in the debate around carbon emissions and climate change.

Speaking at a climate change conference held by the IFA in Dublin this week, Prof Mitloehner outlined how methane (CH4) has a much shorter lifespan of about 10 years compared to the other GHGs such as CO2 and nitrous oxide (N2O), which last for thousands of years in the earth’s atmosphere.

“Once you put CO2 in the atmosphere it pretty much stays there forever. Every time you drive your car you put new CO2 in the atmosphere. CO2 is a one-way street and only goes up and up and up and up,” said Prof Mitloehner.

“But methane is different. While methane is produced, it is also destroyed via a process called hydroxyl oxidation and put away into soils. And that is a very important distinction if we are to properly account for the amount of methane in the atmosphere,” he added.

In essence, Mitloehner is saying that ruminant animals such as cattle are part of a ‘biogenic carbon cycle’, where plants suck CO2 out of the atmosphere in order to grow and convert this carbon into cellulose (grass), the most abundant bio-mass in the world. This cellulose is then eaten by a ruminant animal which converts, or upcycles, it into proteins humans can consume (meat and milk).

While ruminants release carbon (methane) into the atmosphere after digesting this cellulose, Mitloehner argues that this is recycled carbon and therefore not comparable to burning of fossil fuels, which emits new carbon into that atmosphere that has been stored deep in the earth for millions of years.

The UC Davis professor also said his university has done some early research work in California which shows that grasslands could sequester as much carbon as a forest. Mitloehner said the Irish Government needed to prioritise research in this area to validate how much carbon Irish grasslands actually sequester from the atmosphere every year.