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Methane emissions from livestock digestive processes are responsible for approximately 40% of all methane emissions in the United States and 25% worldwide. Decreasing livestock emissions could not only mitigate climate change, but also improve animal health and the efficiency of milk and beef production.

We convened a group of experts on the AskScience subreddit to answer your questions about the quest to reduce livestock methane emissions.

Q&A Highlights

Magdalena (Maggie) Masello –

There’s a suite of interventions that can be used to mitigate methane emissions from livestock. Diet management can be one of them, but we also have other approaches like feed additives, vaccines, and genetic selection (some of which are already available, and others still in development) that can be used to address it. Livestock systems can vary from confined to pasture-based and mixed systems, and not all interventions will be suitable for each system (e.g., not all approaches will be practical in grazing systems, where animals are not handled very frequently).

Most of these strategies focus on reducing enteric methane (i.e., emissions coming out of the animal), but some technologies under development are working on trying to capture the emissions before they reach the atmosphere, like wearable devices that oxidize methane in the exhaled cow’s breath using a catalytic converter.

Most strategies focus on enteric methane since that’s the main methane source (~70% of agriculture methane emissions vs. ~10% coming from manure management). In intensive systems (like dairies in the US), where manure is stored, digesters can be used to capture methane, which can then be used for multiple purposes, including generating electricity to power the dairy farm itself. So yes, dairies can be powered by poop!

Ermias Kebreab –

Seaweed remains a promising solution. To date, over 10 studies conducted globally have reported average methane reductions of more than 40%. Several start-up companies in the U.S., Australia, and Europe are actively working to bring this technology to market. In addition, synthetic alternatives to seaweed have recently shown potential reductions of up to 95%. This continues to be a highly active area of research, with a few long-term studies currently underway.

Kevin Roelofs –

When I tell someone that I work on methane from cows – the seaweed is the most likely thing they will ask me about.

Basically some types of seaweed make a small molecule called bromoform that can inhibit the enzyme that produces methane.

Some of the challenges have been in scaling – it’s actually hard to grow seaweed at large quantities!

Another one has been making sure that the every batch of seaweed has the same amount of bromoform to ensure proper dosing.

Along with the seaweed which is a type of feed additive, there are significant efforts in breeding low-methane animals, changing diets, and developing anti-methanogen vaccines. Probably we will need many solutions to address the needs of different farmers across the world.

Ermias Kebreab –

The microbes that mostly produce methane are not bacteria but methanogens belonging to the domain of Archea. There are solutions that interfere with their ability to produce methane such as Bovaer currently available around the world.

There is research going on to use CRISPR and edit out the gene responsible for methane formation so we can have cows that produce little to no methane.

Kevin Roelofs –

In addition to the new CRISPR approaches, there are several other types of efforts to reduce methanogens.

  • vaccines
  • small molecules that inhibit the methane producing enzyme, and other anti-methanogen antibiotics
  • breeding low-methane cattle
  • changing animal food to promote lower methane emissions
  • improving animal health and intensifying production to get more meat and milk per unit of methane produced
  • introducing probiotics that attempt to redirect energy flows away from methane and towards pathways that provide energy for the animal

etc…

So far, the biggest successes have been with diet, breeding, intensifying production, and improving health and nutrition. Recently the small molecule Bovaer (3NOP) has started to be approved for use in various markets, and hopefully that will make a difference.

Likely we will need many of these solutions to be developed so that different farmers have access to a range of solutions that are suited to the needs of their particular needs.

Ermias Kebreab –

Most antibiotics do not affect methane production as methanogens are not bacteria. However, there are certain antibiotics such as rumensin or monensin that has shown to reduce methane emission by about 3% and increase productivity by about 9%.

Magdalena (Maggie) Masello – Grain-fed cattle typically produce less enteric methane than forage-based diets. This is due to how enteric fermentation works. Briefly, microbes in the rumen (one of the cow’s fore-stomaches) break down feed and produce hydrogen (H2) and carbon dioxide (CO2) as byproducts, which are then used by methanogens (methane-producing microbes in the rumen) to produce methane. Thus, any strategy that reduces H2 availability can help lower methane production. Incorporating grain into a cow’s diet is one such strategy because it shifts rumen fermentation toward propionate production, which consumes H2 that would otherwise be used by methanogens to produce methane (sometimes called a hydrogen “sink”). One thing to consider, though, is that excessive grain supplementation can increase the risk of certain health disorders, like ruminal acidosis and laminitis, so the amount provided must be handled with caution.

Confined systems represent only a small proportion of the global cattle population. Even when considering beef cattle, their time spent confined in feedlots is relatively low (only the last few months of their lives). Thus, most enteric methane emissions are generated from animals while on pasture. If we want to make meaningful progress, that’s where we need to focus most of our efforts!

Ermias Kebreab –

When cow manure is stored in open lagoons, especially during warmer months like spring and summer, it releases methane—a powerful greenhouse gas. But if the manure is kept dry, it doesn’t produce much methane.

One way to deal with this is by using anaerobic digesters, which can capture the methane from manure and turn it into electricity. Depending on the system’s size, it can generate enough power for a few homes—or even an entire community.

Unfortunately, we can’t yet capture methane from cow burps in the same way. The methane in burps is too spread out and diluted. In the future, we might be able to collect some of it from housed cattle operations, but we’re not there yet.

Magdalena (Maggie) Masello –

According to my own experience, these discussions are easier to have in nations like the EU where there is a higher level of public awareness regarding livestock sustainability. Certain South American countries, where I’m from, don’t always have that level of public awareness, so when people talk about livestock emissions, they tend to be a little more skeptical or hesitant, especially in those where livestock production plays a significant role in the economy.

In the case of Ireland, methane accounts for ~74% of their agricultural GHG emissions, with 65% of that coming from enteric methane. Ireland has been very proactive in addressing this issue. For example, Teagasc has done great work creating and launching a national climate action strategy that includes initiatives like the Singpost Advisory Programme. This program involves more than 120 farms across Ireland (with the goal to enroll 50,000 farmers by 2030), serving as the flagship for climate action initiatives.

Links related to experts’ work:

Ample Agriculture

Spark Climate

Livestock and enteric methane (from the UN Food and Agriculture Organization)

Policy for Reducing Methane Emissions from Livestock in the United States

What seaweed and cow burps have to do with climate change

Additional links related to the topic:

Methanogens and Climate Change article from American Society for Microbiology

Teagasc (Agriculture and Food Development Authority in Ireland) Climate Action Strategy

Alternatives to genetically altering organisms:

Available now

In development

 

It’s cow belching (burps), caused by a process called enteric fermentation, that contributes to methane emissions, NOT flatulence (farts).

Did you know?, from NASA
The organisms that produce methane in our (and livestock) guts are methanogens NOT bacteria.
Did you know?, from Am. Soc. of Microbiology

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