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What is AD and Why It’s Better Than Landfills?

In case you’re not familiar with the term and process, let us explain anaerobic digestion (AD) - it is the sustainable process of recycling large amounts of food waste and animal waste. Would you like to learn more about it?

What is Anaerobic Digestion?

Anaerobic digestion is a complex biological process involving the breakdown of organic matter in the absence of oxygen. It takes place in large, sealed, and insulated vessels with controlled heating and mixing.

Food waste enters a sealed building where it is processed into a liquid porridge. It is then pumped into the anaerobic digestion plant. Here, the bacteria feed on the food waste and produce biogas.

This biogas is captured and used as a fuel in Combined Heat and Power (CHP) engines to generate electricity. And, the surplus gas is cleaned up and sent to the national gas grid.

The digestate or biofertiliser produced undergoes pasteurisation to ensure that any pathogens are destroyed and is stored in large lagoons ready to be applied twice a year on farmland.

The use of this high nutrient biofertiliser replaces the use of fossil-fuel-derived fertilisers and ensures a complete loop of carbon and energy capture.

The process is an environmentally friendly way of recycling food waste and transforming it into green energy.

Why is Anaerobic Digestion necessary?

Every year in the UK, around 9.5 million tonnes of food waste is produced, and according to WRAP, around 70% of this was intended for human consumption.

The 2007 Waste Strategy for England from the Government encourages people to take reasonable action on waste. The aim is to reduce the creation and improve the poor disposal of it across the UK.

A growing environmental conscience is now driving businesses and homeowners to consider how they deal with their household and business food waste.

Since food waste is such a large portion of the annual waste, there is a growing demand for food waste recycling facilities.

The reason for this is that food waste being sent to landfills is bad for the environment. Its decomposition creates greenhouse gases, along with a number of other negative effects. By recycling it, we can help the environment.

The food waste recycling facilities recycle food waste in a sustainable and environmentally friendly way, through the anaerobic digestion process. As a result, it has a lesser impact on the planet.

What are the Anaerobic Digestion process steps?

Anaerobic Digestion is a complex biological process that follows a detailed ‘waste recipe’, but it can be broken into the following steps.

  1. Food waste is collected and taken to an AD plant.
  2. Separate food waste – liquid and food waste are mixed together and the process of anaerobic digestion starts.
  3. The hydrolysis process starts – liquid is pumped into tanks and the anaerobic digestion process starts.
  4. Pasteurisation – heat generated by the CHPs is used here to heat the mixture to 70 degrees Celsius for at least an hour to kill any harmful pathogens.
  5. Digestion – the pasteurised feedstock enters the tank and this is where the majority of biogas is captured. The gas naturally rises within the process and is captured and regulated from here.
  6. Electricity–regulated gas is captured and used to generate electricity.
  7. Renewable energy – the energy captured as part of the AD process is 100% renewable and captured in three forms: heat, gas and digestate for nutrient-rich fertiliser.

What are the benefits of Anaerobic Digestion?

Businesses now have to consider their environmental impact as a direct result of how they deal with their food or animal waste. They can reduce their carbon emissions through a more sustainable waste disposal process.

Here are the benefits AD offers in that regard.


Anaerobic Digestion is a low-impact, environmentally friendly process of creating a renewable form of energy from waste. Not only does the waste not end up in landfills, but the resultant byproducts also help provide an alternative source of power and an eco-friendly fertiliser.

Lower cost

Recycling food waste, specifically through anaerobic digestion, instead of disposing of it in landfills can help you save money. That is because the cost of sending waste to landfills per tonne of waste is much higher.

As a result, whilst you still have some cost when recycling your food waste, it is significantly lower than what your cost would be if you sent the waste to a landfill.

Green credentials for your business

Anaerobic Digestion creates a biofuel from waste. More importantly, your waste is not sent to a landfill where it releases greenhouse gases to the atmosphere. Instead, we capture these gases to create a sustainable fuel.

Plus, as a business, you need to report any greenhouse gases that your business produces to the Government. You also need to report if your business adversely impacts the environment in any way.

If you recycle your food waste, you don’t have as many pollutants to report.

As a result, recycling your food waste helps improve your business’s green credentials.

Produces an organic fertiliser

The process produces a high nutrient biofertiliser that replaces the use of fossil-fuel-derived fertilisers on the land. And, it is only fitting that the food from the land feeds the soil, creating the perfect circle of life.

Renewable process

Anaerobic Digestion is a much sought-after, low cost and low-impact process utilising the food and animal waste from the economy. It is a completely renewable process, as it uses waste as the feedstock.

No fossil fuel or non-renewable resources are needed in the process, and the greenhouse gases that would have been created if the waste had been sent to landfills are harnessed for the greater good.


The process is used to generate methane, a biofuel, which is then used to create power. The electricity and gas are then fed to the relevant grids. That reduces the need for traditional fossil fuels for power overall and is also used to power the digestion process, effectively sustaining itself.

What are the byproducts of Anaerobic Digestion?

As we mentioned earlier, the anaerobic digestion process uses organic matter as feedstock. The feedstock is ‘fed’ to microorganisms in a controlled environment. As the bacteria ‘eat’ and digest the waste, they produce methane (CH4).

Methane is an excellent biofuel, which can be burned to produce heat and, consequently, electricity.

Additionally, the residual output, digestate or biofertiliser, is put to good use as fertiliser across local fields. This nutritionally-rich, bioactive fertiliser feeds the soil and reduces the use of harmful and environmentally damaging crop sprays and pesticides.

How do you generate renewable energy from the anaerobic digestion process?

Anaerobic digestion is a complex biological process which produces methane as a byproduct. This gas is collected and sent to the Combined Heat and Power (CHP) units. Here, it is used as a fuel to power the generators which make electricity.

Alternatively, the gas is sent to the gas filter, from where it is passed directly into the power grid. There, it goes on to power boilers, fires etc in homes and businesses.

How is wastewater used in Anaerobic Digestion?

Instead of using fresh water, the Anaerobic Digestion process can safely use wastewater.

As part of the anaerobic digestion process, industrial wastewater is used to create a ‘sludge’ which forms part of the materials that move through the tanks. This water is derived from several sources, for example, as a by-product of the food manufacturing process.

The liquids are all tested before entering the AD sites as all liquid has to be a certain specification to avoid damage to the plant machinery as well as the biology (the microorganisms that power the AD process).

As a result, this is not only a great way of recycling waste but also uses and ‘cleans’ wastewater.

Where can I find an Anaerobic Digestion plant?

Making use of your local AD plants or the facilities within a group of AD plants has its advantages.

BioteCH4 has a number of anaerobic digestion plants across the UK, all with the capability of dealing with large amounts of food waste from across a variety of industries.

Why choose BioteCH4 as your food waste recycling partner?

BioteCH4 is one of the leading producers of anaerobic digestion from food waste in the UK. Across our six sites, we handle the collection, transportation and production of food waste, oils and fats recycling. The work we do here and with our customers helps divert waste from landfills and overall helps the UK achieve its energy targets and cut emissions.

We can provide a cost-effective solution for local authorities and the commercial sector because we understand and deliver on all your food waste requirements.

Our team’s in-depth understanding of the industry means we have the knowledge and expertise to deal with all food waste requirements. Additionally, we also have six AD site locations across the country, including a highly versatile waste transfer station.

That gives us the capacity to handle large volumes of food waste from a variety of sectors, and there is bound to be one near you.

If you’d like to talk to a member of our team about your food waste or anything we’ve mentioned in this blog, then please do not hesitate to get in touch.

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