An anaerobic digestion facility required clarity on its obligations under the Control of Major Accident Hazards (COMAH) Regulations, particularly in relation to the quantity of dangerous substances handled onsite and how this could influence its regulatory classification.
OTECSA Consulting Ltd was commissioned to undertake a targeted assessment to determine whether the site would fall within Lower Tier or Upper Tier COMAH. Given the significant operational, regulatory and cost implications associated with COMAH classification, the client sought a clear and practical understanding of how their current and proposed handling and storage arrangements would impact compliance.
The study was carried out as a desktop exercise using client provided data, with a focus on delivering actionable insights to support operational planning.
COMAH Challenge
he facility handled a combination of flammable gases and stored fuels as part of its normal operations. While these are typical for anaerobic digestion processes, they fall within the scope of COMAH regulations, where exceeding defined thresholds can trigger more stringent compliance requirements.
The client faced uncertainty around how different operating scenarios, particularly variations in the size of propane storage and the number of biomethane trailers onsite, would influence their COMAH status.
A key concern was avoiding an unintentional transition into Upper Tier COMAH, which would introduce:
- Increased regulatory scrutiny
- More extensive safety documentation and reporting
- Higher operational and compliance costs
The client therefore required a clear understanding of the limits within which they could operate while maintaining flexibility for future growth.
Our Approach
We undertook a structured review of the site’s dangerous substances inventory in line with COMAH requirements (Schedule 1 of these regulations). Rather than assessing a single fixed scenario, the study explored a range of realistic operating conditions to provide a more meaningful and practical outcome.
The assessment considered:
- Different sizes of propane storage, used for biomethane upgrading
- Varying numbers of biomethane temporary storage vessels onsite, which was a parameter within the sites control
By analysing these combinations, OTECSA was able to identify how changes in one part of the operation would affect the overall COMAH classification. This scenario-based approach allowed the study to function not just as a compliance check, but as a decision-support tool.
The work was delivered within a short timeframe and structured to allow further iterations as the client continued to refine their operational plans.
Key Insights
The initial assessment identified that under the client’s proposed full-scale operating conditions, the site would fall within Upper Tier COMAH. This highlighted a potential regulatory challenge, as operating at this level would introduce significantly more stringent compliance requirements.
OTECSA subsequently evaluated a range of alternative scenarios to determine how the site could remain within Lower Tier COMAH, while maintaining operational viability.
Key insights included:
- The site’s COMAH classification is strongly influenced by the quantity of propane stored onsite
- There is a direct trade-off between quantity of propane stored onsite and the number of biomethane temporary storage vessels that can be accommodated onsite
- Increasing the quantity of propane stored onsite or transport capacity beyond certain limits would result in the site exceeding Lower Tier thresholds
Overall, the findings demonstrated that relatively small operational changes could have a significant impact on regulatory classification, reinforcing the need for careful planning and control of material inventories.
Business Impact and Value Delivered
The assessment provided the client with a clear and practical understanding of their regulatory boundaries, enabling more confident and informed decision-making.
Specifically, the study enabled the client to:
- Define operational limits for storage and logistics while remaining within Lower Tier COMAH
- Evaluate the impact of future expansion or configuration changes before implementation
- Avoid the risk of unintentionally triggering Upper Tier COMAH requirements
- Align infrastructure planning, such as temporary storage vessel capacity and propane storage provision, with regulatory constraints
By translating regulatory thresholds into clear operational guidance, OTECSA helped the client take a proactive approach to compliance, reducing uncertainty and supporting more efficient planning.
Conclusion
This project highlights the importance of early-stage and scenario-based COMAH assessments in supporting both compliance and operational strategy. Through a structured and flexible approach, OTECSA provided the client with clarity on how key variables, such as propane storage and biomethane trailer volumes, directly influence regulatory classification.
The outcome was not only a clear determination of COMAH status, but also a practical framework to guide future decisions, ensuring that regulatory considerations are effectively integrated into ongoing site operations and development plans.