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The Advantages and Disadvantages of Anaerobic Digestion vs Composting

Anaerobic- digestion vs composting: Making a Comparison

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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 this.

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 requires very good operating practice and detailed monitoring to demonstrate to regulating bodies.
  2. This is the biggest disadvantage! Composting requires the input of quite large energy inputs to aerate and turn the compost piles. By comparison anaerobic digestion wins hands-down for “greenness”, and it makes no contribution to reducing the carbon footprints of 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 (Ground To Ground Blog)

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. … Credits: Anaerobic Digestion: An Alternative To Composting | Ground to

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…. Credits: Pop Quiz: What’s the Difference Between Aerobic Decomposition …

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

Fig. 2 – Schematic Diagram Showing the Anaerobic Digestion Process

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

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

Advantages and Disadvantages of Anaerobic Digestion eBook cover

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7 Responses to The Advantages and Disadvantages of Anaerobic Digestion vs Composting

  1. Dana Sundby October 23, 2016 at 9:31 pm #

    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.

    • Stephen Last January 28, 2017 at 10:34 pm #

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

  2. sami January 2, 2017 at 7:21 am #

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

    • radimin October 7, 2017 at 11:51 pm #

      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.

  3. Peter Ogrady January 28, 2017 at 2:36 am #

    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.

  4. daniyan elijah October 26, 2017 at 12:29 am #

    tanks alot it of great help to my project work

  5. brodie January 8, 2018 at 6:25 pm #

    Thank you for posting this great article. I’m a long time reader however I’ve never actually left a comment.
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    Thanks again for a quality article!

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