Inside the University of California, Davis, dairy barn, a Holstein cow has its head and neck sealed airtight inside a large, clear-plastic chamber that resembles an incubator for newborns. While giant tubes above the chamber pump air in and push air out, the cow calmly stands and eats her feed. Equipment inside a nearby trailer spits out data.
This is how Frank Mitloehner measures gases that come from cows’ stomachs and ultimately contribute to global warming. Quantifying these emissions is key to mitigating them, and Mitloehner is one of several UC Davis researchers investigating economical ways to make livestock production more environmentally sustainable around the globe.
Cattle are the No. 1 agricultural source of greenhouse gases worldwide. Each year, a single cow will belch about 220 pounds of methane, which is shorter lived than carbon dioxide but 28 times more potent in warming the atmosphere, said Mitloehner, a professor and air quality specialist in the Department of Animal Science.
With the escalating effects of climate change, that fact has advocates urging the public to eat less beef. They contend it’s an unsustainable diet in a world with a population expected to reach nearly 10 billion by 2050.
Cows and other ruminants account for just 4 percent of all greenhouse gases produced in the United States, he said, and beef cattle just 2 percent of direct emissions.
Better breeding, genetics and nutrition have increased the efficiency of livestock production in the U.S. In the 1970s, 140 million head of cattle were needed to meet demand. Now, just 90 million head are required. At the same time, those 90 million cattle are producing more meat.
“We’re now feeding more people with fewer cattle,” Mitloehner said.
The global problem
Shrinking livestock’s carbon hoofprint worldwide is a bigger challenge. Livestock are responsible for 14.5 percent of global greenhouse gases.
India, for example, has the world’s largest cattle population, but the lowest beef consumption of any country. As a result, cows live longer and emit more methane over their lifetime. In addition, cows in tropical regions produce less milk and meat, so it takes them longer to get to market.
“If you have hundreds of millions of cattle to achieve a dismal amount of product, then that comes with a high environmental footprint,” Mitloehner said.
Researchers at UC Davis have projects in Vietnam, Ethiopia and Burkina Faso to boost livestock productivity through better nutrition. That may be critical going forward as demand for meat is rising in developing countries.
"We expect by 2050 there is going to be a 300 percent increase in beef demand in Asia," said Ermias Kebreab, a professor of animal science and director of the UC Davis World Food Center.
A new diet
Kebreab, Mitloehner and other UC Davis scientists are looking for ways to make cows more sustainable and less gassy. One way to do that is to make their high-fiber diet easier to digest, so scientists often turn to feed supplements for this purpose. It sounds simple, but finding an affordable and nutritious additive has proved difficult.
However, Kebreab has succeeded in finding such a supplement by feeding dairy cattle a plant way off the trough menu: seaweed.
“We’ve done one trial and showed that there is up to a 60 percent reduction in methane emissions by using 1 percent of seaweed in the diet,” Kebreab said. “This is a very surprising and promising development.”
In addition to reducing methane output, the seaweed doesn’t make the cows’ milk taste bad. He’s now testing the diet on beef cattle. It could be a relatively inexpensive solution for reducing emissions.
This type of red seaweed, called Asparagopsis taxiformis, has one big drawback: a wild harvest is unlikely to provide enough of a supply for broad adoption. Other scientists are looking for ways to grow it to scale, and Kebreab remains hopeful that feed additives hold the most promise.
“I believe that we will have a solution, two or three good candidates, that would reduce emissions quite substantially,” Kebreab said. “I can see that happening in the next few years.”
On the Van Vleck Ranch east of Sacramento near Rancho Murieta, Jerry Spencer manages about 2,500 cattle. A good winter’s rain this year has left them a feast of green pastures. Spencer pays close attention to the grasses, making sure the animals have enough to eat but don’t overgraze. He maintains a diversity of native grasses to keep the cows healthy and rotates herds between pastures to give the plants a rest from grazing and opportunity to recover.
“You want to leave as much as grass as possible to allow water infiltration and healthy root systems,” Spencer said.
(Research at UC Davis indicates just a touch of the ocean algae in cattle feed could dramatically cut greenhouse gas emissions from California’s 1.8 million dairy cows.)
Maintaining healthy root systems isn’t just good for the plants. The longer and denser the roots, the more they can hold atmospheric carbon in the soil.
“One of the best and most simple things we can do on rangelands to help mitigate climate change is to conserve rangeland ecosystems and keep the carbon that’s already stored in rangeland soils safely stored there,” said Ken Tate, a UC Davis rangeland watershed management extension specialist. California is at particular risk of rangelands being converted to housing and other developments, he said.
Ranchers really have little financial incentive to let their herds overgraze or let their herd’s hooves compact and degrade soils. Spencer said if the land degrades, then the cattle’s health can suffer as well.
“Sustainability is keeping everything viable both economically and biologically,” said Spencer. “Ranchers don’t continue to exist if either one of those are really out of balance.”
While sustainable grazing practices won’t eliminate methane produced by the cows, they can offset it. According to Project Drawdown, this solution could sequester 16 gigatons of carbon dioxide by 2050.
“Proper grazing sustains working landscapes that support communities, food production and a healthy environment,” Tate said.
Environmental considerations may factor into people’s food choices, but those decisions are also based on religious and cultural beliefs and traditions, as well as personal tastes. In low-income countries, there may not be any choice. It’s why Tate and Mitloehner believe the meat-free movement can go only so far.
“There will never be a situation where some major part of our diet will be ruled out,” Mitloehner said. “My job is not to judge people for their eating habits. My job is to look at how we can produce livestock and minimize those environmental impacts that do exist.”