Does Compost Produce Methane?

Climate change is a big deal. As the world warms, the water evaporates, leading to more moisture in the air. This means many areas in the world will experience intense rainfall, while others intense snowfall.

We can also expect to see drought in inland areas during hot summers, and more flooding take place from rainstorms and rising sea levels.

Scientists believe we are adding to the natural greenhouse gas, with gases released from industry and agriculture trapping the heat from the sun within the atmosphere and increasing the general temperature… which leads to climate change.

While less abundant than CO2 (carbon dioxide), methane is also one of those dangerous greenhouse gases scientists talk about.

In this article, we are going to talk about methane, and whether we produce methane as we create compost at home – a debated topic in the composting community.

What is Methane?

Methane (CH4) is a colorless, odorless, and highly flammable gas composed of one carbon atom and four hydrogen atoms. It is also the primary component of natural gas and is used to produce heat and electricity around the world.

Since methane is also greenhouse gas, it contributes to global warming. It’s the second most abundant greenhouse gas next to carbon dioxide (CO2), but it’s 25 times as potent as carbon dioxide at trapping heat in the atmosphere.

How is Methane Produced?

There are two major ways in which methane is produced.

The first way is through a series of chemical reactions as organic matter gets decomposed in anaerobic, low-oxygen environments such as bogs and swamps. As plants die and sink into these watery environments, they are broken down by bacteria.

methane bubbles
Methane bubbles in swamp

Wetlands are the single largest natural contributor of methane emissions. Methane can also leak from rice fields, vulcanoes, and termites.

We can also find methane in underground fossil fuel deposits subjected to high temperatures over many millennia. But we release that methane by harvesting, mining, and releasing the fossil fuel present underground.

In fact, human activity causes roughly 50 to 65 percent of U.S. methane emissions, with 30 percent of those emissions being released by the natural gas and petroleum industry.

Also, 27 percent of methane emissions are from a process called enteric fermentation, which is basically cows burping and farting while digesting their food.

Landfills represent a smaller piece of the pie, but they still cause 16 percent of methane emissions. So, by throwing food waste into the trash bin, we are redirecting it to landfills, where it will rot and release methane.

Compost can also generate methane, but you can easily avoid it.

Does Compost Produce Methane?

What compost looks like

We mentioned that methane results from decomposition in an anaerobic, low-oxygen environment. That is basically how a landfill can be defined.

A place where waste is kept while anaerobic digestion occurs – or a process in which microorganisms break down waste without oxygen.

This means the composting process can also produce methane, but that’s only if you completely disregard your compost heap and leave it without care.

If you take care of your compost pile or bin, you’re actually creating an aerobic (oxygenated) environment, incapable of producing methane. You do that by investing your time and effort in creating and maintaining the ideal environment where aerobic microorganisms can thrive and break down your food waste.

Produce Compost Without Generating Methane

The first step is to ensure you have a location to build your compost heap or a place to put your compost bin with at least a cubic yard.

Still… what is more important is to have a good compost setup, with the right size to ensure it’s big enough to build up the proper temperature. If you don’t have the means for a Jora JK270 compost tumbler (capable of holding 9.5 cubic feet or 71 gallons of compost), then the Redmon compost bin is also a good choice.

Once you have a system set up, the next step is to fill it up with alternating layers of browns (carbon) and greens (nitrogen).

“Browns” include carbon-rich materials such as:

  • Sawdust
  • Yard trimmings such as grass, dry leaves, branches, twigs
  • Shredded newspaper, paper, cardboard
  • Sawdust
  • Woodchips
  • Cotton
  • Pine needles
  • Peanut shells
  • Straw
  • Ashes (from wood)
  • Corn stalks.
Cardboard (good carbon source)

They aerate the pile, creating a hospitable environment for the right kinds of microorganisms.

We know that there are three stages in the composting cycles where different microorganisms are active. 1

The first stage starts out with mesophilic microorganisms that quickly break down soluble, readily degradable compounds, and the heat they produce causes the compost temperature to rise.

As the temperatures rise, the heat-loving thermophilic organisms take over the compost to break down organic materials into smaller pieces. Heat is important because it’s more conducive to break down proteins, fats, and complex carbohydrates.

In the meantime, you turn the compost pile to introduce oxygen into the heap… which prevents the temperature from rising above dangerous levels that could exterminate essential microorganisms. Also, by keeping your pile aerated, you discourage any anaerobic, methane-producing bacteria from getting lodged in your pile.

Once the energy supply gets exhausted, the compost temperature gradually decreases and the mesophilic microorganisms take over again and start breaking down the remaining organic materials into usable humus or soil conditioner.

“Greens” include nitrogen-rich materials such as:

  • Vegetable and fruit scraps
  • Coffee grounds
  • Grass clippings
  • Manure
  • Hay
  • Weeds
  • Seaweed
  • Alfalfa
  • Clover.
Vegetable and fruit scraps

Do not include any dairy, meat, bones, oils, or pet poop, as your compost won’t get hot enough to destroy any pathogens in them, and they usually get stinky.

Also – and this is important – ensure that you have a carbon to nitrogen ratio of 25 to 1 or 30 to 1 because it’s the most optimal for rapid decomposition. Microorganisms consume carbon to get energy and release heat. They also feed on nitrogen to grow and reproduce themselves, but having the right balance is essential. 2

Too much carbon in your pile will slow down decomposition and actually reduce the heat generated by microorganisms because they cease to multiply. And too much nitrogen can make your pile release an unpleasant smell and increase its acidity, which is toxic for some species of microorganisms.

Besides the carbon-to-nitrogen ratio, you also need proper moisture (between forty and sixty percent) to have enough dampness to amp up microorganisms, yet enough to keep the pile with healthy oxygen levels. Don’t go overboard with the moisture, otherwise you risk having the aerobic microorganisms drown.

If you follow the advice I gave you above, then you can create compost that will produce no methane, which would be a sign of an unhealthy pile.

Conclusion: So, Does Composting Produce Methane?

Composting is a process that can produce methane, but that is only if you don’t regularly infuse your compost heap with oxygen, and leave it to rot.

If you grab a shovel or pitchfork, you can give your pile a few turns, and that will get some oxygen in and discourage anaerobic, methane-producing bacteria from thriving in your compost.

It’s important to point out that you also need other aspects to ensure you have a healthy compost pile, including classic ones such as:

  • A well-balanced carbon-to-nitrogen ratio
  • Proper level of moisture
  • The willingness to regularly aerate your pile

Compost involves a little trial and error to get right, but once you’re experienced and can replicate the steps over and over again, you will always be able to have a healthy pile.


1 – Cornell University (Compost Microorganisms)

2 – Cornell University (Compost Chemistry)