Cows, Methane, and Climate Change

Over the last couple of centuries, Earth has become warmer. That’s because of greenhouse gases released into the atmosphere. 

One of the most commonly known greenhouse gases is carbon dioxide (CO₂). Carbon dioxide is a colourless, odourless gas. It is released when fossil fuels are burned. Burning fossil fuels releases carbon dioxide into the atmosphere. The carbon in the carbon dioxide was stored for millions of years under the ground in the form of hydrocarbons.

After carbon dioxide, the next most abundant greenhouse gas is methane (CH₄). Although carbon dioxide is much more abundant in the atmosphere than methane, methane traps roughly 30 times more heat than carbon dioxide. This makes methane an important gas to keep an eye on. 

Let’s look more closely at where methane comes from. In particular, let’s look at a source of methane that might surprise you: livestock.

What are the sources of methane emissions?

Methane comes from both natural sources and anthropogenic (human-related) sources. Natural sources include: 

• Wetlands
• bodies of water
• Plant-eating animals (such as elephants, kangaroos, and termites!) 

Human-related sources fall into four main categories:

• Natural gas-based
• Petroleum-based
• Agriculture-based
• Other sources

Agriculture-based sources include rice production, livestock, and manure management. Other sources include the burning of biomass, coal mining, and the treatment of waste in landfills and wastewater. 

How do livestock produce methane?

The beef and dairy cattle industry is one of the main contributors to global greenhouse gases. Methane makes up about half of the total greenhouse gases this sector emits. Cows generate methane in two main ways: through their digestion and through their waste.

Cows are part of a group of animals called ruminants. Ruminants have stomachs with four distinct chambers. Sheep, goats, and giraffes are also ruminants. 

The first chamber is called the rumen. The rumen is home to a complex ecosystem of microorganisms. These include bacteria, fungi, and protozoa. Some bacteria and protozoa break down the sugar and starch from plants. Others break down the cellulose that makes up plant cell walls. 

The second chamber is the reticulum. This is where tough-to-digest plants, like grass, are stored. The plants are regurgitated and chewed again and again. This repeated chewing helps physically break the food down. 

The third chamber is the omasum. It mechanically breaks the food down further. 

The fourth chamber is the abomasum, or true stomach. Here, nutrients are extracted from the food. The food then proceeds through the digestive process. 

Did you know? 

The rumen contains about 200 species of microorganisms. But only about 10% of these play an important role in digestion. 

An important process called enteric fermentation takes place in the rumen. That’s when bacteria break down complex carbohydrates into simple sugars. The end products of enteric fermentation by bacteria include volatile fatty acids (VFAs) as well as gases, such as carbon dioxide and methane. VFAs are absorbed through the walls of the rumen and transported to the liver where the animals use them for energy.

Did you know? 

Cows release methane mainly through their belches (burps). The rest comes out as flatulence (farts).

Can we make cows produce less methane?

What cows eat has a big effect on how much methane they produce. Digesting certain types of food produces more methane than digesting other foods. For example, digesting hay and grass produces more methane than corn. Scientists are studying alternatives to cow feed that may produce less methane. 

For example, scientists are trying adding seaweed to the cows’ food. They hope that seaweed can inhibit a specific enzyme. That enzyme is involved in the production of methane while the cow digests its food. A 2018 experiment showed that adding seaweed to a cow’s diet may reduce their methane production by as much as half! But researchers have found one problem with this solution: cows don’t seem to like the salty taste of seaweed very much!

Other scientists are taking a genetic approach. A study published in 2019 found that the type and amount of methane-producing bacteria found in a cow’s stomach is related to its genetic makeup. Knowing this, scientists can breed cows that have less of these bacteria in their stomachs. This will eventually create a type of genetically-modified cow that produces less methane!

Did you know? 

We share our planet with 1.4 billion cows. Each of these animals produces 250 to 500 litres of methane every day!

What can you do to help fight climate change?

Many people like you and me are always looking for ways to keep greenhouse gas emissions down. For example, many of us choose to walk or bike instead of driving. 

But as you have just learned, methane gas emissions from livestock are a huge problem. So driving less may not be the most important thing we can do to help mitigate climate change. Many experts now believe that eating less meat would actually have a bigger impact.