There are many renewable energy sources out there that recycle organic waste to create new energy.

Let’s take a look at how anaerobic digestion (AD) works to create renewable energy out of organic waste.

What Is Anaerobic Digestion?

Anaerobic Digestion (AD) is the process of breaking down organic matter in the absence of oxygen to produce biogas.

This process occurs naturally in landfills and wastewater treatment facilities, but can also be done in purpose-built digesters.

AD is a promising renewable energy technology because it can divert waste from landfills, generate renewable electricity and heat, and create a nutrient-rich fertilizer.

How Does AD Work?

Organic matter, like food waste, manure, and sewage, contains methane. Methane is a powerful greenhouse gas that contributes to climate change.

When organic matter decomposes in the presence of oxygen (aerobic decomposition), methane is released into the atmosphere.

The following items are generally considered “organic” These things may be digested in a digester:

  • Animal manures;
  • Food scraps;
  • Fats, oils, and greases;
  • Industrial organic residuals; and
  • Sewage sludge (biosolids).

Anaerobic Digestion Energy Production

How does anaerobic digestion make electricity?

To obtain electricity from anaerobic digestion, we burn the biogas in generators.

Although this does produce CO², it is still a carbon-neutral process since all of the CO² generated was taken up by the organic material throughout its life cycle and when new matter develops, the CO² is reabsorbed.

The process is called anaerobic because it takes place in the absence of oxygen in a sealed tank. In the tank, microorganisms break down the organic matter and release biogas.

The gas is about 60-70% methane and 30-40% carbon dioxide. The methane can be used to generate electricity in a generator, and the carbon dioxide can be used for other purposes, like carbonated drinks.

Biogas Production

One of the main benefits of AD is the fact that it can produce biogas, which is a renewable energy source. The methane in biogas can be used to generate electricity, and the carbon dioxide can be used for other purposes, like carbonated drinks.

The process of AD can also create a nutrient-rich fertilizer, which can be used to improve soil quality.

Anaerobic Digestion Of Food Waste

How does anaerobic digestion work with food waste?

Anaerobic digestion happens in the absence of oxygen as bacteria digest organic substances and create biogas.

The method reduces waste volume while also generating biogas, which may be utilized as a fuel source.

Which type of waste is suitable for anaerobic digestion?

The principles behind anaerobic digestion systems are the same whether the feedstock is food waste, animal manures, or wastewater sludge.

The systems may have minor variations in design, but the process is essentially the same.

Anaerobic Digestion Wastewater Treatment

What is the two-stage anaerobic digestion of food waste?

A two-stage anaerobic digestion process is a major innovation in the field of renewable and sustainable energy technology that has the potential to convert organic waste into biomethane and simultaneously resolve the problem of energy scarcity and waste management.

Farming Anaerobic Digesters

A lot of AD actually takes place on farms.

Farmers have long used anaerobic digestion to manage manure and other organic wastes.

Here are the 3 main systems used on farms:

  • Passive Systems: Bio-wastes are treated using a separate recovery process such as anaerobic digesters or solid-liquid separators to turn into biogas. There is no mechanical mixing, and the organic matter must be thin enough to seep through the system.
  • Low Rate Systems: The main source of methane-forming microorganisms is manure flowing through the digester. The manure is kept in the system for 20-60 days before being released.
  • High Rate Systems: Methane-forming microorganisms are constantly being fed into the system through a separate process. This allows for a shorter retention time (15-30 days) and higher methane production.

Anaerobic Digestion Advantages and Disadvantages

Anaerobic Digestion Advantages:

  • Renewable energy source.
  • Reduces greenhouse gas emissions.
  • Can create a nutrient-rich fertilizer.
  • Can reduce waste volume.
  • Diversified Farm Revenue.
  • Rural Economic Growth.
  • Conservation of Agricultural Land.
  • Energy Independence.
  • Sustainable Food Production.
  • Farm-Community Relationships.

Anaerobic Digestion Disadvantages:

  • The initial investment can be costly.
  • Ongoing maintenance costs.
  • The digester must be carefully monitored.
  • Methane emissions (if not used).
  • Low processing capacity.
  • High requirements for the pretreatment of food waste and the ammonia nitrogen; salts are easy to inhibit wet anaerobic digestion.
  • There is a risk of secondary pollution which is difficult to handle biogas residue.


Is anaerobic digestion renewable energy?

Yes, it is. Biogas is a by-product of the anaerobic digestion process. Biogas is a renewable energy source that may be used in a variety of ways. Biogas is utilized by communities and businesses throughout the country to Power engines, and produce mechanical power, heat, and/or electricity (including combined heat and power systems).

What’s the difference between anaerobic digestion and fermentation?

Anaerobic digestion is the breakdown of organic substances without the presence of oxygen. Dark fermentation is a process by which organisms convert organic compounds in the absence of light to produce biogas.

Anaerobic digestion environmental benefits

Anaerobic digestion systems capture methane and allow us to use it in a positive way. Methane is a hazardous greenhouse gas that must be prevented from entering the atmosphere if left unchecked.

How much energy does anaerobic digestion produce?

The energy potential is almost limitless. Each day, when 100 tons of food waste are eaten, an anaerobic digester may generate enough power to power 800 to 1,400 homes each year. The fat, oil, and grease from the food service sector may be fed into an anaerobic digester to improve biogas production.

How many anaerobic digestion plants are there in the UK?

There are 650 operational AD facilities (excluding traditional water treatment plants) in the UK. This is enough to treat around 5% of the country’s food waste.

Is anaerobic digestion recycling or recovery?

In most cases, the major aim of AD waste consignment is to extract energy from it. This implies that the treatment of garbage at an anaerobic digestion facility will generally be classified as “other recovery” in terms of the waste hierarchy.

How much methane does anaerobic digestion produce?

Anaerobic digestion is a well-known technique for treating waste and wastewater. The end product is biogas, which is a combination of methane (55-75%) and carbon dioxide (25-45%), as well as being able to be used for heating, upgrading to natural gas quality, or co-generation of electricity and heat.

Does anaerobic digestion produce greenhouse gases?

Yes, anaerobic digestion produces carbon dioxide, methane, and nitrous oxide. However, the biogas produced by anaerobic digestion can be used as a renewable energy source, which can help to offset the greenhouse gases emitted from the digestion process.

What is the difference between anaerobic digestion and composting?

The two methods are quite similar. The main distinction is that composting is the breakdown of organic material in the presence of air, whereas anaerobic digestion (AD) is the breakdown of organic material without oxygen (and most significantly air).

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