Methane    

While the amount of methane being emitted by cattle may not change year to year how can that mean that there is no impact on temperatures?

As outlined in the video above not all methane is created equal.

Methane generated by ‘life’ is called biogenic methane. One notable source of biogenic methane is ruminants, such as sheep and cattle.

Biogenic methane is any methane created by things alive today and things that have very recently died. That could be from cows, landfills, or microbes in stagnant ponds. This is a major contributor to the agricultural sector’s climate impact. The creation of biogenic methane is intricately linked to the drawdown of carbon dioxide by photosynthesis.

Simply put, when ruminant animals eat grass, methane is released when they belch, and also from their manure. After 12 years or so, that methane breaks down into ‘natural’ or biogenic CO2 and water. The grass absorbs the CO2 through photosynthesis and turns it into carbohydrate. Cows eat the grass, and the whole cycle starts again. 

Methane generated by burning fossil fuels is termed ‘fossil methane’ and its impact on our climate is far more destructive.

Fossil methane is made from carbon that has been stored underground for millions of years far from the surface and the global atmosphere. Virtually all gas burned for energy today is fossil methane, and the production of all fossil fuels involves releasing significant amounts of methane. Releasing this methane involves re-introducing old carbon to the active biosphere that had long ago been removed from the system.

Because of the biogenic cycling of carbon, if livestock numbers stay the same, eventually (in about 12 years), the methane produced by livestock will not contribute additional global warming.

In contrast, CO2 and methane produced from burning fossil fuels, are  new to the atmosphere. They do not stem from the natural carbon cycle. New additions of these gases build on what’s already there, day after day, year after year.

Methane and the biogenic carbon cycle

Diagram courtesy of the Climate Council Australia