What is an anaerobic digestion (AD) plant?
An anaerobic digestion plant or AD plant as otherwise known, is a facility that uses microorganisms to break down organic materials without the use of oxygen inside sealed tanks.
What is an anaerobic digestion plant used for?
Anaerobic digestion plants process a range of organic wastes, feedstocks include:
- Food waste
- Agricultural waste and crop residues
- Animal manures and slurries
- Commercial organic waste
- Industrial food production waste
How does an anaerobic digestion (AD) plant work?
The process typically follows these steps:
1. Feedstock is added to a digester
Organic materials such as food waste, agricultural residues, livestock manures and energy crops are placed into a sealed tank (digester), where microorganisms break down the organic matter in the absence of oxygen.
2. The organic matter is broken down through four stages
Over several weeks, the microorganisms convert the organic material through four main stages:
- Hydrolysis
- Acidogenesis
- Acetogenesis
- Methanogenesis
During this process, much of the organic matter is converted into biogas, while the remaining material becomes digestate.
3. The products are used
Biogas is used to generate electricity and heat, or upgraded to biomethane for injection into the national gas grid or use as a vehicle fuel. Digestate is a nutrient rich material containing nutrients such as nitrogen, phosphorus and potassium, making it suitable for use as an agricultural fertiliser.
What waste is produced by an anaerobic digestion plant?
Although anaerobic digestion is an efficient recycling process, several waste streams and by-products require specialist management. Materials include:
- AD grit
- Digestate fibre
- Digestate screenings
- Depackaging residues
- Plastic contamination
- Compost Like Output (CLO)
- Sewage grit
- Wash plant organic fines
- Clean waste sludge
Site Solutions has the experience and network infrastructure in place to correctly manage such AD plant byproducts. For more information, click here.
What is AD grit?
AD grit (anaerobic digestion grit) is the heavy, non-organic material that accumulates during the digestion process. It commonly consists of sand, stones, grit, glass fragments and other inert contaminants that cannot be broken down via the process.
Over time, this material settles within digesters and storage tanks, reducing operational capacity if it is not removed.
Why does AD grit need to be removed?
Regular AD grit removal helps maintain the efficiency and lifespan of anaerobic digestion equipment. Excessive grit build-up can:
- Reduce digester capacity
- Damage pumps and pipework
- Affect mixing performance
- Increase maintenance costs
- Cause costly plant downtime
Can Site Solutions manage AD plant waste?
Yes. Site Solutions provides nationwide collection, transport and compliant treatment solutions for waste generated by anaerobic digestion plants. We work with a network of approved treatment facilities to ensure waste is managed safely, sustainably and in accordance with environmental legislation.
What AD waste streams can Site Solutions collect?
We provide collection and disposal services for a variety of anaerobic digestion waste streams, including:
- AD grit
- Digestate fibre
- Screenings
- Depackaging residues
- Plastic contamination
- Compost Like Output (CLO)
- Sewage grit
If you have another organic or process waste stream, our team are available to discuss options.
Can you arrange transport from our anaerobic digestion plant?
Yes. We organise nationwide collections using suitable vehicles including walking floor trailers, tippers, articulated lorries and other specialist transport depending on your waste type, volumes and site access.
Is AD waste classified as Animal By-Products (ABP)?
Some waste streams from anaerobic digestion plants are classified as Animal By-Products (ABPs), depending on the feedstock accepted by the facility. We understand the regulations surrounding ABP materials and ensure they are transported and managed through appropriately permitted treatment facilities.
Do you offer one-off collections or regular contracts?
Yes. Whether you’re carrying out a scheduled digester clean-out, responding to an emergency shutdown or require regular collections of AD by-products, we can provide flexible collection schedules to suit your operational needs.
How is AD waste disposed of?
The disposal route depends on the specific waste stream and its composition. Materials may be recycled, recovered or treated at permitted facilities where environmentally appropriate. Site Solutions always seeks the most sustainable and compliant waste management option available.
Do you provide nationwide coverage?
Yes. Site Solutions provides nationwide coverage across the UK through our trusted network of licensed treatment facilities and transport partners. Contact the team with your queries.
