Are methane emissions from cows a big deal?

Yes, cows burp methane. But is this really a problem?




Ruminants have a stomach with four chambers (a rumen) that contains microbes called methanotrophs which decompose and ferment plant materials. This fermentation process, called enteric fermentation, produces methane as a by-product which is released into the atmosphere by cow burps.



But one of the problems with blaming cattle for increasing GHG levels is that there is no discussion of context. The way enteric emissions (burps) are usually measured is either through masks, SF6 tracers, or chambers –> as a result the emission levels are measured out of context from where the cattle live.

When looking at methane emissions, it’s important to look at the entire ecosystem context.

Nature knows best. Nature balances this methane production with methane decomposition. Methanotrophic bacteria, which are aerobic bacteria that thrive in healthy soils, consume and break down atmospheric methane as an energy source! (1) This bacterial action removes roughly 1 billion tons of methane from the atmosphere annually, the equivalent of 23 billion tons of carbon dioxide (2).

Soil-based decomposition of methane may be equal to or greater than ruminant methane production, depending on how the pastures are managed, the soil type and soil health. So, would love to see a study evaluate the NET methane production within intact healthy ecosystems, but not sure if or when this type of study will happen.

While this is certainly good news, unfortunately most conventional farming practices cause considerable damage to these natural methane decomposers.


- Feedlots, which take ruminants out of the natural ecosystem context.


- Poor grazing (for example, over grazing resulting from leaving ruminants on pasture for too long, which can damage the soil structure). This reduces the number of methanotrophic bacteria and reduces the amount of methane oxidized in the soil.  


- Tillage, bare ground and synthetic inputs from conventional Ag production, since these methods and inputs destroy the soil and its ability to operate as a methane (& carbon) sink

So, soil without tillage or synthetic inputs that is continuously covered with plants (a mix of cash and cover crops all year round) and is managed with proper grazing will contain more methanotrophs that will offset the methane created by methanogens in ruminants.

Nature is beautiful and soil/land management is key!


References:

(1) https://www.pnas.org/content/116/17/8515

(2) https://www.amazon.com/Nature-Properties-Soils-15th/dp/0133254488