Building a stronger renewable future

Civils AD Plant

How PDC Engineering Is advancing AD Plant design across the UK & Europe

The renewables sector within the UK has been rapidly expanding over the last decade, with an increasing number of anaerobic digestion (AD) plants constructed throughout Britain and Ireland.

This has been partly driven by the requirement for local councils to put additional focus on food waste, with £295 million of funding injected in 2024 to local councils to facilitate food waste collection from households by 2026 (Gov.UK, 2024). Rather than being sent to rot in landfill, releasing methane directly to the atmosphere, food waste could instead be utilised within the AD process, producing biogas and biofertilizer. Currently, it is estimated that 36 million tonnes of organic waste is sent to AD Plants every year (Business Waste, 2026) and this volume will continue to increase.

Constructing additional AD plants will also aid in the shift towards renewable energy and the movement away from coal and natural gas. Alongside food waste, agricultural waste and crops can be used as a feedstock to fuel the biological process within a plant.

At PDC Engineering, we have experienced this movement towards recycling waste first-hand, with increasing numbers of AD plants being constructed alongside composting facilities and other forms of waste recycling. Having worked on our first AD plants in 2008, we have since gone on to design over 35 newly built plants, alongside reviewing the compliance and condition of over 150 sites per year around the UK. This had led to us gaining a reputation of providing practical, cost-effective solutions, based on a wealth of experience within the industry alongside a desire to continually improve the suitability and quality of our designs.

Working on waste management facilities, whilst not always the most glamorous sites, satisfies the values shared throughout the company of wanting to provide engineering solutions to environmentally beneficial projects.

Compliance Assessments and New Technology

Whilst the market for waste management, recycling, and renewables is increasing, it is vital to ensure that sites being built are not only suitable for operation but also compliant with relevant legislation. The potential adverse environmental impacts from a leak or spillage from a plant could be substantial, with threats including groundwater pollution, eutrophication, and biodiversity loss. Therefore, it is imperative that these sites are designed to suit guidance, operated appropriately, and remediated if required.

CIRIA C736, Containment systems for the prevention of pollution, came into force in 2014, superseding the previous CIRIA R164 (1997) document. This document, applied by the Environment Agency as best guidance and practice, is to be followed by a range of different processing sites, including those previously mentioned. It refers to primary, secondary, and tertiary containment systems, detailing how they should be implemented to contain potentially contaminating liquids within the site boundary. Whilst new-build sites must comply with these regulations, older plants constructed prior to the implementation of C736 may require additional works to bring the plants in line with current requirements.

PDC have been at the forefront of reviewing sites against C736, covering England, Wales, Scotland and Northern Ireland. We provide both assessments of the existing sites, and design solutions to gain compliance for those who currently do not meet the levels necessary to be approved by the Environment Agency. This includes reviews of containment systems, drainage, infrastructure, and internal inspections of tanks and lagoons.

We work closely with our clients to ensure that any solutions are balanced between compliance and feasibility. Liaising between the client and the EA, we assess over 100 sites per year, and this figure continues to grow.

With our experience in design and ability to offer this in-house, we can approach the situation with both a compliance and engineering mindset, ensuring that the final output is buildable and in line with legislation.

Alongside the compliance assessments of the wider site, we have utilised ground penetrating radar (GPR) to assess the condition of tanks and lagoons across numerous sites. We have employed this non-destructive testing method to replace the previous limited schmidt hammer testing favoured by the industry previously. This can be combined with internal tank laser scanning, allowing us to produce a 3D model of the internal condition of a tank, alongside the GPR scanning. Used together, we can then provide information on superficial condition and internal slab condition, not possible from a purely visual review. As a company we aim to be future focused, investing in new technology to provide further services for our clients and to remain at the forefront of consultancy within the industry.

Our Multi-Disciplinary Approach

When constructing an AD Plant, there are a number of steps which must be completed before the build beings. This includes the planning, surveying, and civils design phases of a project, which we provide inhouse. As the project progresses into the build stage, we can also offer construction quality assurance (CQA) checks, plus as-built surveys and condition and compliance checks post-construction. We offer all of these services, promoting a holistic approach utilising a mixture of disciplines within the company. As a client you can rely on us to deliver vital components in house throughout the project, rather than having to liaise between multiple practices, which is both time consuming and costly.

The planning stage is essential for a project to ensure that the permissions gained are practicable when it comes to construction. The multi-disciplinary nature of our business means that engineers can be involved throughout the planning stage to help shape the design with consideration for constructability, creating site-specific layouts which consider the ground profile and conditions, rather than generic plans. Our planning team coordinate both inhouse and external parties to create comprehensive planning packages and manage the process through to securing permissions, remaining in the project background during later stages to ensure the design is compliant with the permission.

Following planning, the design stage must take into account the client’s requirements to provide a set of drawings which can be built from. This includes civil and structural elements within site, such as buildings or drainage infrastructure, working on topographical surveys provided by our in-house surveying team.

To ensure that the site is constructed as specified, we provide CQA checks throughout the build phase, attending site regularly and meeting with contractors and the client. This allows for us to review the installation of various elements of the project as it progresses, highlighting any issues before they become a problem further down the line, whist providing accurate details and records for the client.

Finally, as-built surveys carried out both topographically and for drainage and utilities again allows for a check that everything has been installed as specified and expected, with any snags raised and rectified at the earliest opportunity. The drainage and compliance surveys would then be conducted each year following finalisation of the build, providing condition information and ensuring the site is operating in line with relevant guidelines.

By offering this breadth of services at PDC Engineering, it promotes strong internal collaboration. Surveyors understand the needs of the engineers, designers take into account planning and compliance requirements, and compliance surveyors have clear insight into how and why a site has been constructed in a particular way.

Looking Ahead

As the renewables and waste management markets continue to grow, we are continuing to improve on our service offerings. As mentioned previously, we now offer planning consultancy for new-build sites, along with growing our laser scanning and drone fleet to transition into 3D modelling. We have expanded our coverage of projects to include Northern Ireland and the Republic of Ireland in the last 12 months, providing consultancy remotely and in-person with site visits overseas.

Our Director of Projects, Oliver Jones, is also part of the group updating the current C736 and C759 regulations for CIRIA, allowing us to positively influence the regulatory requirements from a civil engineering perspective, ensuring that the guidance is effective whilst also being feasible.

We are always looking to expand and take on new projects further afield, growing our employee-owned business and helping more clients meet their project targets whilst promoting our values of cost-effective engineering.

Whether you’re planning a new site, upgrading existing infrastructure, or seeking clarity on compliance or containment integrity, our team is ready to support you.

For project enquiries or to request a quotation, contact us at pdc@pdcengineering.co.uk

References:

https://www.gov.uk/government/news/new-295m-for-councils-to-introduce-weekly-food-waste-collections

Title – New £295m for councils to introduce weekly food waste collections

Author – Department of Environment, Food & Rural Affairs and Robbie Moore MP

Published – 25^th March 2024

https://www.businesswaste.co.uk/news/why-the-uk-is-facing-a-food-waste-crisis-as-ad-plants-hit-capacity/

Title – Why the UK is facing a food crisis as AD Plants hits capacity

Author – Mitch Thorne (Senior Content Write at Business Waste)

Published – 21^st November 2025

https://www.ciria.org/CIRIA/Books/Free_publications/C736F.aspx

Title – Containment systems for the prevention of pollution