Best Available Techniques for Storage Tank Emission Control

1. BAT is broader than hardware

In the European industrial-emissions framework, techniques include not only the technology installed but also the way an installation is designed, built, maintained, operated and decommissioned. This distinction matters for tanks because the same nominal equipment can perform very differently depending on inspection, operating practice and maintenance.

The European Emissions from Storage BREF remains a cross-sector reference for storage and transfer. It addresses emissions to air, soil and water and covers fixed-roof and floating-roof tank configurations. EEMUA 213 complements that regulatory perspective with storage-tank guidance focused on reducing VOC emissions at source.

2. Start with the emission mechanism

A BAT review should first establish where the emissions originate. For a fixed-roof tank the dominant issue may be working and standing losses. For a floating-roof tank, the dominant sources may be the rim seal, fittings, seams or roof landings. For a closed system, vent handling and treatment reliability may dominate.

This prevents the technology list from becoming the analysis. A dome may be highly valuable on an external floating-roof tank exposed to weather, but it does not replace the need for an effective floating roof and seals. A high-performance rim seal cannot correct an open gauge-pole path. A vapour recovery unit cannot compensate for poor capture design.

3. The BAT hierarchy for tanks

4. Technical effectiveness must be demonstrated

A BAT claim should be supported by the physical mechanism, applicable test data or emission factors, a realistic installation condition and an understanding of degradation. Nominal efficiency percentages are weak evidence when the boundary conditions are unclear.

For floating roofs, the assessment should include rim-space range, tank geometry, deck penetrations, seam design, product compatibility and operating loads. For vapour treatment, it should include vapour composition, turndown, peak flow, availability, bypass philosophy and what happens during trips or maintenance.

5. BAT is site-specific but not arbitrary

Tank diameter, throughput, vapour pressure, climate, service criticality, existing configuration, outage opportunity and local environmental sensitivity all affect the practical choice. Site-specific does not mean unstructured. The same decision criteria should be applied consistently across the tank population so that differences in outcome can be explained.

A terminal-wide BAT review is therefore stronger when it uses a common inventory, a consistent calculation basis and an explicit gap assessment rather than treating each project independently.

6. Safety and integrity remain boundary conditions

Emission reduction must not create a new integrity or process-safety problem. Vent restrictions must remain compatible with pressure/vacuum design. Floating-roof modifications must preserve buoyancy, structural capacity, drainage and fire-protection interfaces. Seal modifications must tolerate the actual shell geometry and roof movement.

The best environmental technique is not acceptable if it undermines safe operation. Equally, a safety argument should not be used as a blanket reason to avoid emission reduction when the conflict can be engineered out.

7. Lifecycle BAT

A technique that is highly effective when new but difficult to inspect, sensitive to installation quality or dependent on consumable sealing materials may have a different lifecycle performance from its initial test result. BAT reviews should therefore consider maintainability, inspection access, expected degradation, repairability and the ability to verify performance after intervention.

This lifecycle view links BAT directly to asset integrity and to the RBI approach developed elsewhere in this whitepaper series.

8. Document the decision

A defensible BAT record should state the baseline, the significant emission sources, applicable requirements, techniques considered, expected reduction, assumptions, safety and integrity constraints, lifecycle implications, economics, implementation plan and verification method. The value of the record is that it preserves why the selected solution was judged appropriate—not merely what was installed.