Crofthead Anaerobic Digestion Plant

Client Name
ARC Development / IONA Capital
  • Sustainable waste management
  • Process engineering
  • Environmental management, permitting & compliance


The Crofthead anaerobic digestion plant will process 99,000 tpa of agricultural waste to produce 499 kW electricity and heat from an onsite CHP, and 500 Nm3/h of biomethane for onsite grid injection. The plant will generate solid and liquid digestate that will receive end-of-waste designation and are taken off site as product.

The plant includes solid and liquid feeding systems, digesters, pasteurisation system, separator, gas cleaning system, gas upgrader, propane supply and grid entry unit.

The site operates under a PPC Permit issued by SEPA and has a secondary containment system. The site benefits from Non-Domestic Renewable Heat Incentive (RHI) payments from OFGEM.


SLR fulfilled the role of Owner’s Engineer including the following:

Design Review;
Process safety support, representing the client at HAZOP and DSEAR studies;

  • Supervision of civils works;
  • Supervision of process installation;
  • Supervision of commissioning;
  • Witnessing of performance testing;
  • Managing the snagging process;
  • Chairing meetings;
  • Co-ordination of the gas to grid works;
  • Managed the connection of phone, broadband and water utilities;


  • Project Management – Chaired progress meetings, update calls and managed trackers for the project.
  • Technical reviewer – Reviewed the plant design, and continued to provide supervision during the civils and process engineering phases.
  • Commissioning – Functionality and commissioning tests witness, managing performance testing in relation to EPC obligations.
  • Legislative compliance – Support with SEPA permitting process.