Anaerobic Digestion and In-Vessel Composting are the processes at the heart of our business. 

Our compost provides an ecological and nitrogen-rich chemical free alternative to synthetic fertilisers in agriculture. 

In-vessel composting

Established in 2005, our team has over a decade’s experience in effective and safe process management. 

Our In-Vessel-Composting plant takes co-mingled food and garden waste, and turns it into premium grade compost. An accelerated version of the natural composting process, the green and food waste is composted within a bunker style system, and then transported for maturation within a separate compost hall, over 8000m2, over a 6 week period. It is then screened as required to produce various grades of compost.



Anaerobic Digestion plant

Established in 2011, our Anaerobic Digestion plant has unrivalled levels of operational continuity having been managed by the same experienced operational team since commissioning. Capacity, which was significantly increased in 2017, is now over 2MW across two CHP engines, and the plant has the capacity to accept 35,000t per annum of waste food.

The plant has a track record of high levels of operational efficiency. This is a measure relating to load factor and engine availability; Whilst the UK industry standard as of 2016 is just over 70%, our plant has consistently achieved an average operational efficiency of over 90%.

The food waste we collect is cleanly separated from any packaging when it arrives at the Anaerobic Digestion plant. The dry packaging is suitable for use within RDF/SRF processes thereby avoiding landfill entirely. The food is then processed into a liquid and fed into large tanks in the absence of oxygen. This liquid food undergoes a natural biological process during the next 30 days where it breaks down into methane and carbon dioxide gases. The methane is then used as a fuel to feed the CHP engine that generates heat and electricity. The heat is used as part of the Anaerobic Digestion process and the electricity is exported to the grid, for use by homes and businesses across the country.

Anaerobic Digestion also generates large volumes of liquid digestate which is stored in tanks on site. This liquor is used by local farmers as a fertiliser. This digestate is PAS-110 accredited and approved by QMS for use in growing crops on arable land.This means Anaerobic Digestion has twin carbon benefits, both reducing reliance on fossil fuels and avoiding the use of synthetic fertilisers in agriculture.

How does Anaerobic Digestion and In-vessel composting work?

The diagrams below show the process of anaerobic digestion and in-vessel composting that we use at Earnside Energy.

The process diagrams show how we transform waste into valuable resources, producing green energy, compost and nutrient-rich organic fertilisers, which contribute to the circular economy.



Anaerobic Digestion

Food waste

Pretreatment – depackaging, shredding and liquefaction

Anaerobic digestion

Digestate produced to PAS110 and stored

Digestate used as a fertiliser for Agriculture

Biogas produced and stored

Renewable energy produced from biogas…100% renewable


Power generated is exported for use in Scottish homes and businesses

In vessel composting

Biodegradable waste collected

Shredding – to create homogenous material

Blending – Creating optimal moisture content and density

In-Vessel composting, containing material for 5-7 days

Microbial action generating heat

Material maintained at 65 degrees centigrade for min 8 hour

Continued bulk maturation in Maturation Building

Matured compost

Screening, to remove material over 40mm particle size

PAS100 Product is no longer classified as waste

Agricultural Fertiliser