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The Advantages and Disadvantages of Anaerobic Digestion vs Composting

Image illustrates the benefits of Anaerobic digestion vs composting: Making a Comparison. Anaerobic digestion pros and cons.
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What are the advantages and disadvantages of anaerobic digestion vs composting is a question asked by a large number of people. Many of our readers who are familiar with composting, but who are thinking more widely about the subject of recycling organic waste and have just heard about Anaerobic Digestion want to know the anaerobic digestion pros and cons.

If this is you, read on while we answer the question: “Which is best, anaerobic digestion, or the much simpler and lower capital cost method of composting?”

First of all the two processes are very much the same. The crucial difference is that composting is the decomposition of organic matter in the presence of air (oxygen) and anaerobic digestion (AD) is the decomposition of organic matter, without air (and most importantly oxygen) present.

Now we make the case for each process by listing the advantages and disadvantages of anaerobic digestion vs composting below:

Advantages of Anaerobic Digestion

  1. It is a net energy producing process which produces renewable energy in the form of biogas.
  2. It produces a liquid and a fibrous fertilizer.
  3. It sanitizes the feedstock/ waste which is put through it, as long as the temperature is held above a required temperature for a pre-defined time period.
  4. It reduces odour below unprocessed waste odour levels.
  5. It is much less likely to cause environmental pollution than spreading untreated organic waste on land.
  6. The effect of the fertilizer is longer lasting than for untreated organic waste.

Disadvantages of Anaerobic Digestion

  1. When carried out at a commercial scale on farms and at wastewater treatment works (WwTWs) it requires a high level of investment in large tanks and other process vessels.
  2. If run inefficiently AD can cause an odour nuisance.

Advantages of Composting

  1. Lower initial capital investment needed to start of composting facility than is needed for an AD Plant.
  2. A slightly lower level of training is needed to run a composting plant the is required for an AD Plant.
  3. It produces a solid output/ fertilizer only. For some this will be an advantage, but in general this digestate product is a neutral factor, neither positive or negative for composting.
  4. It has the same advantages as for AD (items 3 to 6 inclusive) over spreading untreated organic waste material on land.

Disadvantages of Composting

  1. Like anaerobic digestion, it is necessary to pasteurize the composted material to ensure that all infectious agents have been effectively removed. This can be done by ensuring that it composts rapidly and raises its own temperature, through the heat produced during composting.But, ensuring that every batch self-sanitises itself this way requires very good operating practice. and detailed monitoring to demonstrate successful pasteurize to regulating bodies.
  2. This is the biggest disadvantage! Composting requires the input of quite large energy inputs to fuel and operate the equipment needed to aerate and turn the compost piles.By comparison anaerobic digestion wins hands-down for “greenness” by providing its own power to do this.Composting makes no contribution to reducing the carbon footprints of the businesses that use the composting process.By comparison AD Plants can assist businesses by reducing their carbon footprint.
  3. Like AD, if run inefficiently composting can cause an odour nuisance.

We also found the following blog articles which discuss anaerobic digestion vs composting as follows, which you might find interesting to read:

Anaerobic Digestion – an Alternative to Composting

Similar to composting, in AD bacteria consume organic waste such as food scraps, silage, and animal waste and generate an environmentally benign byproduct that can be used as a natural fertilizer. Unlike composting, however, AD also produces biogas, which consists of about 2/3 methane (CH4). Natural gas is methane with a small amount of other trace gases, so biogas can be used as fuel like natural gas. … via .ADAlternativeToComposting

What’s the Difference Between Anaerobic Digestion and Aerobic Decomposition

Yes, one is with and the other without oxygen, and both divert waste from the landfill—but in terms of the end products, what is the advantage of anaerobic digestion? Simply put, does society face a shortage of compost or renewable energy?

In San Francisco, the green compost bins are ubiquitous. Even the food trucks are required to place bins alongside their trucks for compost, recyclables, and trash. Result: the city is diverting an enormous amount of trash from the landfill to help meet its zero-waste goal and producing lots of compost in the process – a process which also produces a lot of carbon dioxide, “the primary greenhouse gas emitted through human activities,” according to the EPA.

A few cities are taking an alternative, more expensive approach to diverting this organic waste called anaerobic digestion and in the process also producing biomethane that is captured for use in electricity generation or used as a transportation fuel. And from a “carbon intensity” perspective, this biogas, also called renewable natural gas, scores at the bottom of carbon intensity chart for California’s Low Carbon Fuel Standard, i.e. it is one of the cleanest of all transportation fuels…. Pop Quiz Difference

Anaerobic Digestion vs Composting: Another Way to Compare the “Aerobic” Process of Composting with “Anaerobic” Digestion is to compare the simplified process diagrams which we show below:

Aerobic digestion - known as composting
Fig. 1 – Schematic Diagram Showing the Aerobic Digestion Process
Anaerobic digestion schematic diagram
Fig. 2 – Schematic Diagram Showing the Anaerobic Digestion Process

(Source: Advanced Biological Treatment of Municipal Solid Waste, Defra UK, 2007)

Anaerobic Digestion vs Composting – Conclusion

There are advantages to both anaerobic digestion and composting, and certainly applying either before green garden waste, or other organic waste is spread on the land, is better than not processing these materials at all.

On balance the preferred process is anaerobic digestion.

The primary reason that anaerobic digestion is considered more sustainable than composting is that composting requires an energy input to carry out the process. The energy is used in the power needed to turn the compost piles during composting.

The fact that anaerobic digestion:

  • produces biogas (a renewable energy source which burns cleanly), and that
  • biogas plants make more energy than they consume to operate,

are generally the factors that make anaerobic digestion the best, most sustainable, option.


Energy Balance Benefits and Feedstock Issues

Although composting (IVC or in Windrows) and anaerobic digestion (AD) treat similar wastes, they are in fact complimentary and not competing technologies.

From an energy consumption and greenhouse gas emission reduction point of view, there is merit in having an AD stage first following by composting.

The benefit of an AD process is that it produces energy in the form of biogas, whereas composting will generally use energy in the processing stages, in aerating the waste and treating any leachate arising from the process. Although the AD liquor which comes out of an AD plant often needs treating, the energy required is available from the biogas.

The digestate from AD often needs to be matured by composting before it can be applied to land.

Since the AD process has reduced the total amount of material (which has been removed as gas), less energy should be required than if the whole amount of waste was treated through composting.

Notwithstanding these issues, some proportions of materials are inherently better suited to either composting or anaerobic digestion.

For example, high proportions of green waste with much bulky wood material is better suited to composting processes as it is easier to handle and has less gas production. Conversely, high proportions of kitchen waste are better suited to AD processes as the gas production potential is
higher and odour control is easier to achieve.


We hope that you found this article useful. If so, and you have a moment to do this. We would greatly appreciate your comments.

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  1. Reply

    I liked your site a lot. I’m taking an online course on Water Quality Technology from the UW-Moraine Park and I found this very useful in helping me write a paper on alternate methods of sludge stabilization. Thanks.

    1. Reply

      Thanks for your feedback. It is appreciated, and it is good to hear that you found some useful information for your paper.

    • sami
    • January 2, 2017

    why aerobic degradation is faster than anaerobic degradation????????????

      • radimin
      • October 7, 2017

      I think that the normally given answer the AD experts will give you is that the methanogenic archaea that do the anaerobic degradation, are a lot slower growing (metabolising) than their aerobic equivalents. I hope that helps you.

    • Peter Ogrady
    • January 28, 2017

    The reason that aerobic degradation is faster than anaerobic degradation is that the anaerobic organisms (methanogens) that do the degrading in anaerobic systems are slow growing at normal ambient (atmospheric) temperatures. They grow faster at higher temperatures. If you look on the web you will see that in hot tropical climates it is much more common to see small domestic biogas plants. Those un-insulated tansk don’t work so well in cooler climates.

  2. Reply

    tanks alot it of great help to my project work

    • brodie
    • January 8, 2018

    Thank you for posting this great article. I’m a long time reader however I’ve never actually left a comment.
    I’ve bookmarked your site and shared this on Facebook.

    Thanks again for a quality article!

  3. Reply

    Your writing is very well received by me. At first my view was to say that anaerobic digestion was not preferable to composting, now I see that you are telling us the opposite. The fertiliser is a much needed product for farmers I am sure.

    • Alice Araujo
    • May 8, 2018

    The Advantages of Anaerobic Digestion are many. Thanks to Brazilian-German Project on energy from Biogas – PROBIOGAS (DKTI). In May 2016, a biogas project based on agricultural residues with a capacity of about 21 MW won an energy auction for the first time. The energy will be priced at EUR 70/MWh, and it will start producing electricity from 2021.

  4. Reply

    Hello there,

    My name is Aly and I would like to know if you would have any interest to have your website here at promoted as a resource on our blog ?

    We are in the midst of updating our broken link resources to include current and up to date resources for our readers. Our resource links are manually approved allowing us to mark a link as a do-follow link as well.

    If you may be interested please in being included as a resource on our blog, please let me know.


    • Hanno Halonen
    • August 28, 2018

    Hi. Thank you for the informative writing and article. Some people are using the heat generated from composting to heat water/interior spaces, so perhaps that could be added to the advances of composting.

    • Baz
    • November 17, 2018

    Hello there,

    Would like to know if you would have any interest to have your website here at promoted as a resource on our blog. If so mail me to the email I just used for this post.

    We are in the midst of updating our broken link resources to include current and up to date resources for our readers. Our resource links are manually approved.

    If you may be interested please in being included as a resource on our blog, please let me know.


    1. Reply

      Baz – Yes. I mailed you.

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