Introduction
A COMAH tier classification assessment can play a critical role in helping operators understand their regulatory obligations and make informed operational decisions. For anaerobic digestion facilities, where flammable gases and fuels are routinely handled and stored, understanding how dangerous substance inventories affect COMAH status is essential.
OTECSA Consulting carried out a COMAH tier classification assessment for an anaerobic digestion facility to determine whether the site would fall within Lower Tier or Upper Tier COMAH. Given the significant operational, regulatory and financial implications associated with COMAH classification, the client required clear guidance on how their storage and operational arrangements could influence compliance requirements.
The study was completed as a desktop assessment using client-supplied information and focused on providing practical recommendations to support future planning.
Why Was a COMAH Classification Assessment Required?
The facility handled a combination of flammable gases and stored fuels as part of normal operations. These materials fall within the scope of the Control of Major Accident Hazards (COMAH) Regulations, where exceeding specified thresholds can trigger additional regulatory requirements.
However, the client faced uncertainty regarding how different operating scenarios would affect their COMAH status, particularly:
- Changes in propane storage capacity used for biomethane upgrading
- Variations in the number of biomethane temporary storage vessels onsite
A key concern was avoiding an unintended transition into Upper Tier COMAH, which would introduce:
- Increased regulatory oversight
- Additional safety documentation requirements
- More extensive reporting obligations
- Higher compliance and operational costs
The client therefore sought a COMAH classification assessment that would clearly define operational limits while maintaining flexibility for future growth.
How Was the COMAH Classification Assessment Conducted?
OTECSA undertook a structured review of the site’s dangerous substances inventory in accordance with Schedule 1 of the COMAH Regulations.
Rather than reviewing a single operating case, the COMAH classification assessment examined multiple realistic scenarios to provide a more useful and practical outcome.
The assessment considered:
- Different propane storage capacities
- Varying numbers of biomethane temporary storage vessels
- Potential future operating configurations
- The interaction between fuel storage and transport arrangements
As a result, the scenario-based approach transformed the assessment from a simple compliance exercise into a practical decision-making tool that supported future operational planning.
What Did the Assessment Reveal?
The initial COMAH classification assessment identified that the client’s proposed full-scale operating configuration would place the facility within Upper Tier COMAH.
This finding highlighted a significant regulatory challenge because Upper Tier COMAH introduces substantially more demanding compliance requirements.
OTECSA therefore explored a range of alternative operating scenarios to identify options that would allow the facility to remain within Lower Tier COMAH while maintaining operational viability.
Consequently, several important findings emerged.
Propane Storage Was a Key Driver
The quantity of propane stored onsite had a significant influence on the site’s COMAH classification.
Relatively small changes in propane inventory could materially affect the overall dangerous substances calculation and determine whether Lower Tier thresholds were exceeded.
Biomethane Storage Capacity Influenced Compliance
The assessment demonstrated a direct relationship between propane storage volumes and the number of biomethane temporary storage vessels that could be accommodated onsite.
As one parameter increased, the available margin for the other decreased.
Small Operational Changes Had Significant Regulatory Consequences
One of the most valuable outcomes of the COMAH classification assessment was demonstrating how seemingly minor operational changes could result in a different regulatory classification.
This reinforced the importance of careful inventory management and strategic planning.
What Value Did the COMAH Classification Assessment Deliver?
The study provided the client with a clear understanding of the operational boundaries within which they could safely and compliantly operate.
Specifically, the assessment enabled the client to:
- Define practical storage and logistics limits
- Understand the regulatory impact of future expansion plans
- Avoid unintentionally triggering Upper Tier COMAH requirements
- Align infrastructure investment with regulatory constraints
- Make informed decisions regarding propane and biomethane storage arrangements
By translating regulatory thresholds into practical operational guidance, OTECSA helped reduce uncertainty and improve planning confidence.
Why Are Scenario-Based COMAH Assessments Valuable?
A scenario-based COMAH classification assessment provides significantly more value than a simple snapshot review.
Furthermore, by evaluating multiple operating conditions, organisations can:
- Understand the sensitivity of their COMAH status to operational changes
- Assess future growth opportunities
- Identify regulatory constraints before capital investment decisions are made
- Develop more robust long-term compliance strategies
This approach supports proactive decision-making rather than reactive compliance management.
Conclusion
This COMAH classification assessment demonstrates the value of early-stage regulatory reviews for anaerobic digestion facilities and other sites handling dangerous substances.
Through a structured assessment of propane and biomethane storage scenarios, OTECSA provided the client with clarity on their COMAH obligations and the operational limits needed to maintain their preferred regulatory status.
The result was not only a determination of COMAH classification but also a practical framework that enables future operational decisions to be made with compliance considerations fully understood.
Need Support with COMAH Classification?
Whether you are developing a new facility, expanding an existing operation, or reviewing dangerous substances inventories, a COMAH classification assessment can help you understand your regulatory obligations and avoid unexpected compliance challenges.
Get in touch with OTECSA to discuss how we can support your COMAH assessments, regulatory strategy and major accident hazard management.