Two researchers in the College of Food, Agricultural and Environmental Sciences at Ohio State University are studying how to cut methane gas produced by cows and reduce the phosphorus and nitrogen that end up in their manure — and potentially waterways.

Across the globe, livestock emit 14.5% of all greenhouse gases (methane, carbon dioxide, nitrous oxide and fluorinated gases) released in the environment, and over half that comes specifically from cows, according to a United Nations report.

With every episode of gas, and especially burping, cattle release methane, which is 23 times more harmful than carbon dioxide, the main greenhouse gas in car emissions.

Besides a cow’s gas, the phosphorus and nitrogen in cow manure applied to farmland has the potential to run off into local waterways, including Lake Erie, contributing to algal blooms that turn the water green and can produce toxins harmful to drinking water.

OSU molecular biologist Zhongtang Yu is working to reduce the amount of methane cattle give off by improving their digestion.

Another CFAES researcher, Chanhee Lee, an assistant professor of animal sciences, is focusing on reducing the waste of cows — solids and gases. In his studies, Lee is testing the effectiveness of adding chemical or biological substances to cow feed to reduce the methane they produce. He also is putting additives in manure to lessen the nitrogen and phosphorus in it, thus reducing the odds of those compounds seeping into surface water.

Reducing methane with natural additives
As methane producers, cattle top humans — by a lot. In one day, a cow generates 200 liters of methane, on average, while humans who produce methane (only one-third of humans do), give off a fraction of a liter of methane daily.

Reducing the methane gas cattle generate not only cuts greenhouse gas emissions, but also potentially allows more of the feed cattle consume to be directed to their body and production. That can lead to larger, stronger animals, and more milk and beef, Yu says.

“Methane is bad because not only is it a greenhouse gas, but it’s a waste of feed,” he explains.

Between 4% and 12% of the feed cattle eat is wasted through the methane gas they produce, Yu says.

If cows have less gas and fewer burps, it is not only more pleasant for the people who work around them, but “they may be able to grow faster, have more meat and produce more milk,” he says.

Yu’s current research examines how natural compounds can reduce the number of protozoa in a cow’s stomach, thus decreasing the amount of methane and nitrogen the cow expels. Any protein that cattle eat that’s not used by their bodies comes out in their urine and manure in the form of nitrogen. Almost half the nitrogen in their urine and manure turns into ammonia gas, which is a toxic, potentially explosive gas, though not a greenhouse gas.

Different compounds can reduce the methane generated in a cow’s gut. Antibiotics are among them. But consumers sometimes steer away from buying beef that’s been given antibiotics, so Yu has opted for testing compounds from natural sources. He’s found that essential oils — including garlic, rosemary and oregano oils — as well as saponins and tannins, are effective in reducing the amount of methane cattle give off in their gas and burps. Saponins are compounds found in some vegetables, beans and herbs. Tannins are bitter-tasting organic substances derived from some plants.

The essential oils, saponins and tannins reduce methane production by decreasing the numbers and activity of protozoa and methane-producing microorganisms in cattle’s guts. The protozoa don’t produce methane, but they help the microorganisms that do, called methanogens. Methanogens are in human guts as well, but not nearly as many as in cattle.

Yu targets the protozoa in a cow’s stomach because they cause the cow to not only produce more methane, but also release more nitrogen into manure.

In his research, Yu’s graduate and undergraduate students take samples from the stomachs of cows and bring them into the lab.

“It doesn’t bother them,” Yu says of his students dealing with the generally chunky and smelly samples.

As a next step, the samples are combined with essential oils, saponins and tannins to see the effect on the protozoa and how much methane is produced. Yu’s lab has found that combinations of a few compounds, substances or both are more effective than individual compounds in reducing methane emission.

Lee, an assistant professor of animal sciences in CFAES, is studying the effect of giving cows 3-nitrooxypropanol, a white powder that can be mixed with their feed. So far, the additive has been shown to cut methane production by up to 20%, depending on the amount given.

Further studies are needed to determine that 3-nitrooxypropanol does not reduce the cattle’s production ability or have any undesirable side effects, Lee notes.

In testing the effectiveness of 3-nitrooxypropanol, a group of cows, each housed in individual stalls, is given feed with or without the compound. Then their gas is measured.

“Cattle are releasing methane by burping almost every minute,” Lee says.

Cutting N and P
Lee’s research aims to reduce the methane gas cows expel, and to cut the nitrogen and phosphorus excreted in their manure. He studies whether the amount of protein and phosphorus in the national feed requirements for beef and dairy cattle can be reduced without jeopardizing the nutrition and strength of the cow.

Some farmers feed their animals more phosphorus than the requirements call for in hopes of boosting the cows’ production levels. But, he says, this is happening less and less.

“Most farmers know well about the dangers of doing this,” Lee adds.

The risk of giving cows more phosphorous or other nutrients is that the excess lands in their manure and urine, Lee says.

But even after that happens, there’s an opportunity to reduce the environmental effects of that waste. Lee is testing whether a chemical or biological additive put in cow manure can change the decomposition of the manure so it gives off less methane gas. Also, he is testing whether a different additive can limit the amount of nitrogen in the manure that turns into ammonia gas as the manure decomposes. Reducing the nitrogen losses from manure can also improve the quality of the manure as a fertilizer.

“We want to reduce the environmental impact of a cow’s waste, but we also want to improve the cow’s ability to produce,” Lee says. “We are going to have significant worldwide population growth, and we need to feed all those people.”

Source: OSUE