Yasuo Kobayashi

Preventing Global Warming by Reducing Burping in Cows

Yasuo Kobayashi , Professor

Research Faculty of Agriculture/ Graduate School of Agriculture

High school : Kyoto Prefectural Ayabe High School

Academic background : Doctorate from Hokkaido University

Research areas
Livestock nutrition, Digestive tract microbiology
Research keywords
cows, methane, global warming, rumen, microorganisms, cashew nuts

What are you trying to achieve?

It is said that cows are one of the contributors to global warming due to the fact that they burp methane. We are researching ways to control the activity of microorganisms that live inside cows’ stomachs, and encourage digestive fermentation that ensures that they release as little methane as possible. There are about 3.1 billion cattle, sheep and goats being raised globally, and the greenhouse gases they produce account for about 5% of the world’s total emissions (more than 30% of emissions in some countries). Reducing this would make an effective contribution to controlling global warming.

Cows have four stomachs. Their first stomach (rumen) is about the size of a household bath. The rumen contains several hundred types of microorganisms in quantities between several hundred trillion and a thousand trillion. The grass eaten by the cow is broken down and subjected to fermentation through the power of these microorganisms. Thanks to these microorganisms, the grass is converted into milk and meat. However, a byproduct of the fermentation is methane gas (between 300-500? per day). If this gas remained in the stomach, it would, of course, burst, but cows burp the methane out into the atmosphere and therefore survive without problem.

Since methane is 23 times more damaging as a greenhouse gas than CO2, when calculated over 365 days, a cow produces the equivalent to approximately 2 tons of CO2 – roughly the same amount as that produced by a family car traveling around 10,000 km per year. This means that cows are making as great a contribution to global warming as automobiles. As a result, the spotlight is currently on research being carried out globally into how to minimize the problematic production of methane by cows.


What methods do you use in your research?

We are trying to change the combination of microorganisms in the rumen so as not to produce methane. It’s a bit like reallocating students to different classes at school. We are trying to create an “eco-class” by selectively choosing certain microorganism members, so that the cow will not produce as much methane (some microorganisms inhibit its production, but some increase it). Selection of microorganisms can be done by adding antibiotics to the cows’ food, but we don’t like using antibiotics. We have searched for safer, more natural substances that have specific antibacterial effects, and we feed those to the cows in order to select the microorganisms we want to be present.

We have been working in partnership with a private-sector company, testing the effectiveness of vegetable oils with antibacterial properties, and finally we have arrived at a byproduct of cashew nuts (Fig. 1). The oily liquid that is extracted from the shells of the nuts (cashew shell fluid) acts as a selective antibacterial, and has been found to have the capability to convert the microorganisms in a cow’s rumen into an “eco-class”. We have demonstrated that cashew shell fluid inhibits the bacteria that supply the materials for methane, as well as the strong methane-producing bacteria. Genetic analysis of many of the members in the microorganism group was immensely helpful in understanding this mechanism. Methods of using gene sequencing to look at changes in the complex combination of microorganisms in the rumen (a look at how the members of the “class” were coming and going) were far more accurate than conventional culture methods, and gave much quicker results (Fig. 1).


How is this going to affect our day-to-day lives?

Global warming is an environmental danger at a global level, which has been brought about by the activities of human beings. The increasing number of livestock in the world means that we can eat hamburgers and cheese regularly, and our diet has improved significantly compared to the past. At the same time, however, the former Beatles Paul McCartney has now proposed a No Beef Day, in order to reduce of effect of burping cows on global warming.

We need to solve this difficult problem using frontline science. Cashew shell fluid – an unexpected byproduct of cashew nuts – has begun to gather attention as a methane reducing agent. As a result of our research results, it was approved a few years ago for domestic use as a raw material for animal feed. Mixing it with cow feed has been shown to reduce the methane in cow burps by 20 to 40%.

Reducing methane is not only good for the environment, it also allows savings in feed consumption that was previously lost in the form of methane. It therefore makes it possible for farmers to give their animals less feed but retain the same yields of milk and meat. We believe that this may be a revolutionary method of maintaining both food and livestock (the very essence of human culture), while making a contribution towards the solution of a difficult environmental problem. Our research has been featured on TV news and environmental programs, as well as in videos broadcast on trains on the Yamanote Line. Please see our website for a more detailed explanation.