Methane formation in the cow's stomach: The feed is broken down by fermentation, producing CO2, H2 and fatty acids. These are converted by methanogens (methane-producing microorganisms) into methane (CH4) and water. The methane leaves the cow through both the mouth and the anus. Methanogenesis is the microbial formation of methane. The process is shown here schematically and simplified; the cow's stomach consists of 4 parts, and the process shown here occurs essentially in the rumen.
<a href="//commons.wikimedia.org/wiki/User:Hgrobe" title="User:Hgrobe">Hannes Grobe</a>,   <a class="external text" href="https://commons.wikimedia.org/wiki/File:Grazing,_Dierhagen_(_1100746).jpg">Matti Blume: Foto der Kuh</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>