What doesn’t stink is that Pennsylvania State University researchers, led by Alexander N. Hristrov, have now demonstrated that feeding 3-nitrooxypropanol (3NOP) to dairy cows over a 12-week period reduces the animals’ methane emissions by 30% (Proc. Natl. Acad. Sci. USA2015, DOI: 1073/pnas.1504124112). 3NOP inhibits methyl coenzyme-M reductase, an enzyme used by bacteria in a cow’s gut.

These symbiotic bacteria produce methane when they help cows digest grass and other fiber-rich foods in the animals’ diet. To test the possibility of mitigating this production without disrupting a cow’s digestion, Hristov and his colleagues mixed additives containing three different concentrations of 3NOP as well as a placebo additive into cattle feed. Then they administered it to 48 Holstein cows for three months.

The rate of methane emission fell in all the animals, except for those receiving the placebo. Scientists have discovered several other methane production inhibitors, but 3NOP appears to be the first to achieve a meaningful effect while being safe for cows’ health and the environment.