Aerobic Vs. Anaerobic Composting: Which Method is the Better Choice?

aerobic composting
Both aerobic and anaerobic composting are decomposition processes by living organisms that convert kitchen waste and other compost materials to make compost through chemical reactions. The significant difference is that aerobic composting requires oxygen, while anaerobic composting does not. Aerobic decomposition is better than anaerobic.

What Is Aerobic Composting?

Aerobic composting involves using oxygen-dependent bacteria to complete the decomposition of organic matter. 

Composting is an organic process driven by naturally occurring microbes that thrive in the moisture present around the organic waste. Microbes can take in oxygen from the surrounding air since it has made its way into the dampness.

Aerobic composting is effective, but it takes a lot of work because you must monitor the temperature and moisture levels.

Some of the characteristics of aerobic composting include:

  • Aerobic composting requires turning at regular intervals to maintain enough aeration. This composting process works best in the open air and can handle various materials.
  • We introduce air to the mixture via a piping system and bulking agents that are stacked loosely.
  • Aerating the piles may be more of a challenge in locations with cooler temperatures. It is still necessary to keep a constant eye on the temperature. 
  • We can use an aerated static compost pile indoors or out, depending on the availability of enough ventilation.
  • In most cases, you can have finished compost in 3 to 6 months using an aerated static pile.

Aerobic composting effectively kills hazardous bacteria and pathogens because the high temperature is too much for these organisms to handle.

Some beneficial bacteria species, like thermophilic bacteria, flourish in these conditions.

5 Types of Aerobic Composting

The different aerobic composting methods include:

1. Open Pile

You have a large heap of organic material here. But to make this work, you need to add a bulking agent.

These include wood shavings, wood chips, cardboard, sawdust, and dry leaves.

2. Windrow 

Most commercial composting operations use this aerobic composting process.

Windrows are long, narrow rows or mounds used to store organic material, and a windrow turner is used to turn the rows regularly.

3. Static Pile

Static piles comprise windrows of unturned organic matter. Pile aeration occurs from below, and the piles are often covered.

4. In-Vessel

You fill an enormous container with organic material, making rotation possible and regulating the humidity, airflow, and temperature.

5. Vermicomposting

Worms create an aerobic compost pile because they exhale via their skin. Here, the worms are your helpers.

It goes faster this way, and the temperature and the level of odor stay low throughout the process.

What Is Anaerobic Composting?

Anaerobic composting involves the microbial breakdown of organic materials without oxygen. It is like natural processes in wetlands, marshes, and bogs that produce peat and moss.

Anaerobic composting, also known as anaerobic digestion, is piling organic waste and allowing it to decompose without using oxygen.

Characteristics of anaerobic composting include:

  • This procedure will not require any upkeep or turning. 
  • Composting without the use of oxygen results in the production of methane, which can have a powerful odor.
  • The high water content of nitrogen-rich materials makes them ideal for anaerobic composting; ‌virtually any organic matter can be digested in an anaerobic composter, including cardboard and paper scraps, grass clippings, food waste, and animal byproducts.
  • It’s best to keep the amount of carbon-rich items like sawdust and dry leaves to a minimum. Adding too much of these dry materials will slow down or stop the anaerobic composting process, leading to an unpleasant odor or the death of the anaerobic microorganisms and the transition to aerobic composting.

3 Types of Anaerobic Composting

The types of anaerobic composting include:

1. Bokashi Composting

Bokashi composting is a centuries-old method used by farmers because it is an anaerobic decomposition process. While heat and soil microbes decompose plant debris in conventional composting, we use beneficial microbes in Bokashi.

Food scraps of any kind, not just plant-based ones, can be composted using the Bokashi composting system. Bokashi composting employs a fermentation process that requires four to six weeks to decompose organic materials. 

You can use it indoors or outdoors because of the acidity’s ability to eradicate dangerous pathogens.

There are two steps involved – the fermentation process begins with the degradation of food waste, which is then completed by soil microbes.

2. Container Composting

If you don’t have access to the microorganisms required by the Bokashi method, an airtight container will offer the perfect condition for anaerobic composting.

A sealed trash bag, airtight plastic bucket, or composting bin will work. You can use 50 to 95% moisture in the container.

Because of its high acidity, compost made using a closed container should age 6-12 months.

3. Submerged Composting

One approach to keep composting materials from releasing unpleasant odors is to keep them underwater. The unwanted gases will be trapped and released slowly in materials containing 80% or higher moisture content. 

Regular water changes are necessary to prevent unpleasant odors from accumulating. Because the water produces an anaerobic environment, we can use this technique with either an open or closed system.

Which Is Better, Anaerobic or Aerobic Decomposition?

Aerobic decomposition is better than anaerobic. During aerobic composting, the only byproducts are water, heat, and a trace quantity of carbon dioxide.

Carbon dioxide is a greenhouse gas but isn’t nearly as harmful as methane. It’s only 1/20th as harmful.

Methane is released during anaerobic composting. And it’s a much more potent greenhouse gas than carbon dioxide.

Is Vermicomposting Aerobic or Anaerobic?

Vermicomposting falls under aerobic composting.

Worms are classified as living creatures and can breathe using their skin. Therefore, composting using worms, also known as “vermicomposting,” is an aerobic process.

What Happens if Compost Goes Anaerobic?

Anaerobic microorganisms predominate and produce intermediate compounds like hydrogen sulfide, organic acids, and methane, among others. These chemicals will continue to build without oxygen since they will not be digested. 

Many of these chemicals emit pungent odors, while some are phytotoxic. Because anaerobic composting occurs at a low temperature, the weed seeds and pathogens in the material are not destroyed.

How Do You Know if Compost Is Anaerobic?

Look for these signs to determine if your compost is anaerobic:

1. Color

Waterlogged anaerobic soils have a homogeneous dull grey appearance instead of red, brown, or black—coloration results from gleying, which is the anaerobic bacteria’s consumption or decrease of manganese or iron.

2. Texture

Even with little rainfall for a while, anaerobic soils are typically wet, sticky, and somewhat heavy because your soil is soggy.

That can occur when a high water table or a clay layer prevents further rainwater absorption.

3. Smell

Anaerobically decomposed soils generally smell rotten, sulfurous, ammonia-like, or even like sweat or urine.

4. No Soil Organisms

When soil is healthy, it is full of life, and you will see earthworms, insects, and other critters.

However, because oxygen is required for biological life to thrive in soil, these organisms are absent (or in substantially lower numbers) in anaerobic soil.

Can Anaerobic Compost Be Saved?

Your anaerobic compost is still salvageable.

To proceed, follow the instructions below:

1. Turn Your Compost

Regularly stirring the compost pile using a pitchfork will promote aeration if the area is small or the compost pile is manageable.

By doing so, oxygen and air can enter the heap. Since oxygen is poisonous to anaerobes, they will perish as well.

2. Add More Carbon

Ammonia scents come from too many nitrogen-rich items like coffee grounds and veggie scraps decaying in the compost pile.

Bringing the carbon concentration to the same level as the nitrogen is the solution.

When you do this, you will give extra energy to the microorganisms that decompose the nitrogen-rich materials.

3. Include Soil Amendments

You can improve the aeration and porosity of dense, compacted, and anaerobic compost by adding dry, coarse, and bulking soil additions like wood chips and leaves. That will allow oxygen to enter the compost more efficiently and enhance its overall aeration.

Use a shovel or pitchfork to work the amendment into the ground after spreading it out in a 3-inch layer over the soil. It is vital to disperse the amendment uniformly over the soil, so there are no untouched regions.

Add your amendments about 4 and 6 weeks before you plant to give the microorganisms in the soil ample time to incorporate them into your soil further.

4. Cut Back on Watering

Waterlogging is one of the primary factors contributing to the formation of anaerobic soils.

Waterlogging can occur in even well-drained soils, like sand, if you apply excessive water frequently.

Reduce the frequency of watering and only water when the soil is nearly dry if it has proper drainage but remains soggy.


Discovering composting as a way of life or even better, as nature’s way of recycling, Ana dedicates her time to trying out new methods of composting at home. Her goal is to share everything that she’s learned in the hopes that it will help others discover the amazing rewards of composting.

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