Warming Signs: Corralling Cattle Emissions Could Help Save the PlanetScience Features Warming Signs
Last week, I talked about how some ruminant animals, like cows, are contributing to climate change. Now it’s time for the good news—how farmers and scientists are limiting those emissions. There are two main ways: changing what goes in, and managing what comes out.
What Goes In …
Changing what cows eat is one of the best ways to reduce emissions from enteric fermentation (the digestion process).
Grass vs. Gas
Let’s start with the simple stuff: Cows already eat grass, so why reinvent the wheel? Danish scientists have been working on a super grass that cows could digest more efficiently—thus reducing the number of burps necessary. As a bonus, they also hope this grass will help cows produce more milk. But more grass does not always translate into less gas; eating non-Danish grass (and hay) usually makes a cow gassier than a diet heavier in grain.
Feeling a Little Italian
Adding a little seasoning might have a big effect, though. Researchers in Wales found that adding garlic to a cow’s food could cut the gas they produced in half. And, because scientists apparently have no concern for cows’ breath, they tried onions next. It worked, for much the same reason as the garlic; the two share similar chemical properties. However, the next step was making sure the onion taste didn’t permeate the milk; luckily, researchers found that a limited amount was easier to stomach in milk taste tests.
Although 3-NOP, a chemical compound, has something of a branding problem—the name’s just not very catchy!—adding it to feed has been shown to reduce methane emissions by 30 percent, without affecting the cow’s weight or milk production.
Nautical by Nature
By far the most effective solution, though, has been a surprise contender: Seaweed. When a certain species of seaweed made up only 2 percent of a cow’s diet, it reduced emissions by a stunning 99 percent in the lab and as much as 70 percent in field tests. It would seem that a compound called bromoform, found in the red species Asparagopsis taxiformis, more or less eliminates the production of methane during digestion.
The next question, of course, is how livestock farmers can get enough of this kind of seaweed to feed the world’s cattle. Globally, seaweed farmers produce about 27 million tons of the algae each year, although that number includes thousands of different types, not just A. taxiformis.
But this news gives a whole new meaning to surf and turf!
… Must Come Out
Image: Courtesy of U.S. Department of Agriculture CC BY 2.0
Just as important as what cows eat, however, is how their waste is managed. While enteric fermentation—burps and farts—make up the most livestock-related methane emissions globally, manure is a close number-two.
Recent regulations about manure management have dairy farmers worried. A new California law announced last September will require dairy farmers to reduce methane emissions from manure drastically: to 40 percent below 2013 levels by 2030. While it will be difficult to implement changes so quickly, there are a few long-term solutions for dealing with waste more efficiently—and even making a buck off it.
Storage Is Key
As manure decomposes, it releases methane—especially when it’s stored in large liquid tanks. These tanks are popular in places like California, which is a major dairy producer.
A working dairy cow can produce 150 pounds of poop every day. Often it’s easier to store it all in enormous tanks, especially when the cows live in barns instead of out on the range, as is often the case for dairy cattle. However, keeping all this moist manure in one place often means it releases more methane, in addition to posing other safety hazards.
Allowing manure to dry helps prevent methane emissions, but it means dealing with mountains of crap. Other storage (and transportation) solutions may be needed, especially for farmers transitioning from liquid tanks.
Capitalize on Natural Gas
One solution for farmers using liquid tanks involves capturing the methane from manure in biogas digesters. Once the biogas, including methane, is captured, it can either be flared off (burned) or, even better, used to generate electricity—which can be used on the farm or sold to utilities for an extra revenue stream.
Of course, it takes some effort and money (MOO-lah?) to set up and maintain the equipment for selling electricity to utility companies. Capturing biogas usually works best for larger operations, such as farmers with 300 cows or more, and the costs of these technologies are often prohibitive for smaller farms. But some states, like Minnesota, offer production incentives and free or low-cost loans for livestock producers to get started.
Another, lower-tech solution—especially for smaller farms—is a return to using, selling, or giving away manure as fertilizer. Using organic fertilizers, instead of chemical fertilizers, can also help mitigate climate change; chemical fertilizers are a significant source of nitrous oxide emissions, another greenhouse gas.
Cut Back on Antibiotics
Remember how I said last week that bacteria helps cows digest their food? It turns out, cows treated with antibiotics produced manure with nearly twice as much methane as their unmedicated peers.
Bonus: Bovine Backpacks
Changing up cows’ diet and manure management is important. But some cattle farmers in Argentina have devised another way to control emissions: capturing as many as 300 liters of methane a day with bovine backpacks. They certainly sound futuristic!
These innovations wouldn’t just reduce greenhouse gas emissions. Many of the climate-friendly feed additives also have the potential to make dairy cattle more productive—which would mean we need fewer cows to get the same milk. And harnessing biogas and fertilizer could help farmers make a buck or two on energy and fertilizer.
Image: Dineshraj Goomany CC BY-SA 2.0
Melody Schreiber is a freelance journalist based in Washington, D.C.