3D fluorescence of rumen ciliate, Entodinium caudatum. Credit: Chuanqi Jiang, Jinying He, and Che Hu / Institute of Hydrobiology, Chinese Academy of Sciences When cows burp, they send a substantial amount of methane gas into the air, which makes them a leading contributor to greenhouse gas emissions. According to research published in the journal Science, a newly discovered hydrogen-producing structure within the microbes of cow stomachs may influence how much of that gas is expelled. The methane process Cows are ruminant mammals with a digestive system that breaks down food in a four-chambered stomach. Inside the rumen, microbes ferment tough plant fibers, such as grass, releasing hydrogen and carbon dioxide as waste products. Other microbes, called methanogens, then combine the two gases to create methane. As cows can't use this for anything useful, it is expelled, predominantly when they burp. But they are not the only tiny organisms involved.…