Do Compost Piles Produce Methane?

Perhaps you’re explaining your composting process to a friend, and they ask, “Did you know compost piles produce methane?” If you incorporate composting into your daily routine as an effort to reduce your impact on global warming, this could come as a shock to you. 

So, now, you’re researching the process and whether this friend of yours is correct. It can’t be true, right? You compost as a way to give back to the environment, not accelerate its demise, so why would this simple task contribute to such a thing?

As you research the topic, you may be surprised by what you find. However, before you write off composting altogether, read through this article. Composting isn’t as good or bad as you might think, but it’s certainly better than the alternative!

Does Compost Release Greenhouse Gas?

The composting process does release greenhouse gases in the form of methane and carbon dioxide. Although carbon dioxide is often blamed for climate change and the greenhouse effect, a few more factors are at play here. 

We won’t go over everything, as that would take a while. However, the point here is that carbon dioxide isn’t the only gas to blame. Unfortunately, methane is also a potent greenhouse gas that can result from composting. Studies show methane is 80 times more powerful at warming over 20 years than carbon dioxide. 

Due to these studies, it’s no surprise that people are concerned with composting. Most folks compost to reduce the amount of waste they send to the landfill or produce nutrient-rich soil amendments for their garden. So, this raises concerns, especially in relation to significant pressing matters like climate change. 

Is Composting Bad for The Environment?

Although composting produces several greenhouse gases, including methane and carbon dioxide, it isn’t necessarily bad for the environment. Instead of focusing on the inherent release of greenhouse gas, we need to focus on the bigger picture. 

Yes – composting releases greenhouse gases. However, the decomposition process of that organic material is going to produce these gases, whether it’s in your backyard compost pile or at the landfill. 

So, we need to take a step back. Unfortunately, roughly ⅓ of the food produced worldwide is wasted. For example, consider corn on the cob. We eat the corn kernels from the cob but toss the rest. Or, consider an apple – we eat the sweet, fruity flesh but throw away the core. 

Although composting these food scraps will contribute to the warming effect, reducing the amount of wasted food can have a much larger impact on climate change as a whole. While producing organic waste is inevitable, and we can’t stop these scraps from producing gases as they decompose, we can look at the problem from a different view. 

Composting At Home vs. The Landfill

For most homeowners, there are only two options when it comes to organic waste: compost it in the backyard or toss it in the trash, where it’ll eventually end up in the landfill. Composting at home is usually aerobic while rotting in a dump is typically anaerobic. 

How so? Before we answer this question, we need to understand what happens in a compost pile. For organic matter to break down, there need to be organisms and bacteria present. These organisms and bacteria work through the waste, breaking it down into a rich soil amendment. 

To further confuse things, there are two types of bacteria in a compost pile: aerobic and anaerobic. The aerobic bacteria are your “composting friends” and require oxygen to do their job, and their output is carbon dioxide. 

On the flip side, anaerobic bacteria don’t need oxygen to decompose the organic matter. However, even though they can still do their job, they’re the “bad composting neighbors” since they produce methane as a product of the process. 

Composting At Home

When you compost organic waste at home, the waste is usually digested by aerobic bacteria. They need oxygen, so you need to regularly turn your compost pile to ensure there’s plenty of air for the bacteria to do their work. 

Your composting pile shouldn’t smell foul – if it does, it’s probably too wet or poorly mixed. Instead, compost should emit a fresh, earthy smell, like when you disturb settled leaves on a walk through the forest. 

Aerobic organisms will work more quickly than their anaerobic counterparts as long as they have enough air access. When the pile is compact, the aerobic microorganisms won’t be able to do their job, slowing the composting process considerably. 

As long as there’s oxygen present in the pile, methane-producing microbes aren’t active. So, you can put your fears to rest, as your compost pile isn’t producing excessive methane. Of course, it does produce carbon dioxide, but this gas is considerably less harmful in the grand scheme of things than methane emissions. 

Composting At The Landfill

For some folks, composting at home simply isn’t feasible. So, what happens when your organic food waste goes to the landfill? Once your food waste reaches the landfill, it doesn’t break down right away like it would in a compost pile.

Many times, there isn’t enough oxygen for aerobic organisms to work. So, anaerobic microbes take over. Instead of producing carbon dioxide as a byproduct of the decomposition process, these microbes produce methane. 

Anaerobic fermentation in these settings is typical, especially in landfills and open stockpiles (such as manure piles). Since 1970, global emissions from waste have nearly doubled, now producing roughly 3% of anthropogenic (human origin) emissions. Of those emissions, almost half come from anaerobic fermentation of solid waste disposal on land (landfills).

For example, consider the 700,000 tonnes of organic waste material that Western Australia composted in 2012. The entirety of this material was broken down via anaerobic fermentation. Every tonne that was broken down by anaerobic fermentation produces roughly one ton of carbon dioxide equivalents of greenhouse gases, primarily in the form of methane. 

Methane is substantially more potent in contributing to global warming than carbon dioxide (although they both do contribute), so the emissions from composting in a landfill are considerable. 

Should I Stop Composting?

If your main reason for not composting is the environmental effect, consider the alternative. Composting in an aerobic setting at home is considerably more environmentally friendly than composting anaerobically in a landfill. 

You can repurpose your organic food waste at home, turning it into an excellent soil amendment. While the process will generate some carbon dioxide, it will generate methane in a landfill setting. So, in the grand scheme of things, it might be better to compost your food waste at home. 

Keep the pile aerated to give your aerobic friends a helping hand, and avoid oversaturating the pile. Here’s a guide on how much water you should use and what to do if you add too much.

If composting at home isn’t feasible, consider looking into local composting companies. There might be a composting service in your area where you can bring your food waste for composting. This is a better alternative to tossing your household’s organic waste in the trash, but sometimes, that might be the only option.