Question: As a vegetarian, I often consider preaching that cow farts are depleting our ozone layer. This consideration was directly sparked from a movie called Cowspiracy on Netflix that highlighted the detrimental effects that factory farming has on the Earth. I would like to know more about the effects of methane on the ozone via cows, and am interested to see if there has been any research directly analyzing the effects.

Answer: With sustainability as a forefront issue concerning the Earth’s growing population, cows continue to release and excrete roughly 20% of the world’s emissions. Methane gas release traps more heat than carbon dioxide in the atmosphere making livestock farming a principal suspect for the release of greenhouse gases and subsequent depletion of the ozone layer. As seen in the figure below, the process concerning the gas release begins with the ingestion of plant material by a cow. As a cow ingests feed or plant material, it then undergoes bacterial digestion and fermentation producing H2 and CO2  as products. Further, methanogenesis occurs in the rumen. It is a process in which methane is released into the environment by certain microbes called methanogens where some products remain in the rumen and methane is processed through the stomach and released by belching or flatus. Specifically, archaebacteria is responsible for the source of greenhouse gas release in sources such as cows, swamplands and rice fields. Scientists are working to develop a type of feed that contains extra nitrogen. In this way  available for the methanogens to instead form ammonia with the excess hydrogen instead of versus methane. To expand this idea, the scientists discussed investigated the need for continued research on hydrogenases from archaebacteria cells, and the need to discover methods to create a structural catalyst that may assist in the function, production and monitoring of methane release. Additional research into the gut microbiome of cows may prove to be an effective way to mitigate the release of methane gas. A study published in the Agriculture, Ecosystems and Environment journal suggested that engineering a way to increase the presence of probiotic agents in the gut would to help improve the digestibility of food, while also providing livestock with other general health benefits. In an effort to analyze the effects of methane, some sources note that grass-fed cows use excess water and land than grain-fed cows, and they “contribute to roughly 40-60% more methane gas release.” Although some other sources suggest that the right pasture could reduce methane emission, livestock still digest grass at a smaller rate than grain and they are often farmed for an extended period of time, each of which are potential situations that may contribute to a greater or extended release of the gas. Although there has been a lot of research done so far on methane gas, further research concerning the release of greenhouse gases by cows fed alternative feed could help identify ways to decrease their detrimental 250 liter release of methane per day.


  • Carla T. 


Beil, Laura (2015, Nov). Getting creative to cut methane from cows. Science News, 188 (11): 12. Web.

Kimble-Evans, Amanda (2010, Dec). Grass-fed cows emit less methane. Mother Earth News 243 (1): 19.

Nyman, Patty (2014, Aug). Pseudo-Sustainability: The Beef With Grass-Fed Beef. One Green Planet. Web

New insight into biochemical methane production. Max-Planck-Gesellschaft: Structural Biology Vonck (2013, Mar).

O’Mara, Peggy (2007, Nov). Sustainable you. Mothering, 124(10): 10,12,14. Web