Anaerobic Digestion
Transforming food waste into renewable energy and fertiliser.
Anaerobic digestion is how ReFood transforms food waste into renewable energy and fertiliser. It's a natural process, carefully managed in our best-in-class facilities, where food waste is safely and efficiently broken down to create valuable outputs.
We often describe it as being similar to the human digestive system. Food waste enters a controlled environment, is broken down by naturally occurring microorganisms, energy is extracted, and the remaining nutrients are returned to the land. The key difference is that in our process, nothing is wasted; the energy is captured and used, rather than lost.
Below is the step-by-step process at ReFood.
How we transform food waste
We use the UK's most advanced Anaerobic Digestion technology to provide an end-to-end recycling process that creates renewable energy and fertiliser from waste.
01
Food Waste Arrives
Collected food waste is delivered to ReFood facilities. Each load given to our team to be checked, recorded, and accepted in accordance with strict intake procedures. Our checks ensures only suitable material enters the process and that full traceability is maintained from the moment waste arrives on site.
02
Preparing the Feedstock
Before digestion begins, food waste is prepared to be processed efficiently. Packaging and non-organic materials are removed, then solid and liquid food waste streams are combined and blended to create a slurry suitable for digestion.
This slurry is transferred into a receiving tank, which acts as a controlled storage and buffer stage. This allows the process to run steadily, manage incoming volumes, and maintain consistent feed into the next stages of treatment.
03
Pasteurisation
From the receiving tank, the slurry passes through a pasteurisation stage. During this step, the material is heated for a controlled period to remove harmful pathogens.
This ensure the digestion process remains protected, the final fertiliser product is safe for agricultural use, and operations remain fully compliant with Animal By-Products and environmental regulations.
04
Mix Tank
After pasteurisation, the material is then transferred to a mixing tank, where it is blended and balanced to achieve the desired consistency for digestion.
Creating a uniform feedstock at this stage allows the digestion process to run steadily and reliably, supporting consistent energy and fertiliser output.
05
The Digestion Stage
The prepared feedstock is pumped into sealed digestion tanks. Inside, naturally occurring microorganisms break down the material in the absence of oxygen. As they work, they release biogas, a gas rich in usable energy.
Because this takes place in a closed, carefully monitored environment, the process remains stable, safe, and efficient at all times.
06
Biogas into Energy
The biogas produced during digestion is captured and used as a renewable energy source. Across the ReFood network, this energy is utilised in two ways. At some facilities, biogas generates renewable electricity, which is exported to the grid to power homes and businesses.
At other facilities, biogas is upgraded to biomethane and injected directly into the national gas grid, supplying renewable gas to homes and industry. Using both approaches allows ReFood to maximise energy recovery and support the transition away from fossil fuels.
07
Creating fertiliser
After digestion, the remaining material is nutrient-rich digestate. At ReFood, this becomes ReGrow, our PAS110-certified fertiliser. Before ReGrow is supplied to farms, it passes through controlled quality checks. Screening processes remove physical contaminants, and the product is monitored to maintain consistent nutrient characteristics. This ensures the fertiliser is safe, reliable, and suitable for agricultural use.
ReGrow is then applied to farmland to improve soil health and support the growth of future food crops, returning nutrients to the land and completing the natural cycle.
08
Closed-Loop System
From food waste to energy and fertiliser, every stage of anaerobic digestion at ReFood is managed, monitored, and controlled by our teams.
The result is a fully closed-loop process in which food waste is not simply removed but transformed into clean energy, healthy soil, and measurable environmental benefits.
