Know what really stinks? The gas that livestock such as cattle release during digestion. These animals produce a quarter of the anthropogenic methane in the U.S.
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.
Ingestion of 3NOP also helped the cows gain weight, increasing the efficiency of their feed. “When we feed an animal, [about] 7% of the energy in the feed is gone as methane,” Hristov says. “Anytime you save a little bit of that, it can be used for other purposes the animal needs,” such as producing milk.
Hristov’s team is planning further studies to investigate how a cow’s gut bacteria continue fermenting grass and other fiber-based foods while being inhibited by 3NOP.
Researchers hope the energy savings and reduced methane emissions offered by 3NOP will help ease climate change. “Agriculture is a key methane source in the U.S.,” says Scot Miller, a fellow at the Carnegie Institution for Science. “Policymakers will likely need to take a multifaceted approach to reduce net U.S. methane emissions. I hope that the work presented in this paper will give us another tool to add to that toolbox.”