From generator to guard tank: chain of custody for ULO

Give every load one traceable identity

A unique consignment identifier should begin at collection and remain attached to transport, receipt, sampling, tank allocation and final disposition. The record should identify the generator, collector, transporter, receiving facility, dates, quantities and measurement method.

Licences, waste descriptions, analytical certificates, seal numbers and incident records should be linked rather than stored as disconnected documents. Controls must prevent duplicate identifiers, undocumented tank transfers and unapproved retrospective changes.

• Record transfer acknowledgement at each custody change.
• Keep rejected and diverted loads within the same traceability system.
• Preserve an audit trail for corrections and exceptional losses.

Connect the ledger to physical samples

Documentary custody is weak if a later sample cannot be tied to the load it represents. Risk-based pre-collection or receipt samples should carry the consignment ID, sampling point, time, sampler and seal details.

Guard tanks or locked quarantine tanks protect the wider inventory until required results are accepted. When source information, sample integrity or acceptance evidence is incomplete, the load should not be commingled. A digital ledger cannot repair an unrepresentative sample.

• Seal and retain duplicate samples under a defined retention plan.
• Record every transfer of sample custody.
• Investigate seal failures, missing samples and unexplained tank movements.

Reconcile physical inventory without false precision

The operational balance is: opening inventory plus verified receipts equals closing inventory plus shipments, process outputs, residues, measured losses and authorised adjustments. Reconciliation should be performed by tank, load and reporting period.

The method must state whether quantities are mass or volume, the reference temperature, density method, meter calibration and expected uncertainty. Unexplained differences require investigation rather than routine balancing entries. This control does not independently prove chemical identity, recycled content or avoided emissions.

Where an organisation intends to attribute characteristics through a mass-balance chain-of-custody model, ISO 22095-2:2026 provides requirements for boundaries, accounting and attribution. Any self-declared environmental claim should also be assessed under the applicable claims rules, including ISO 14021:2026 where relevant.

• Set tolerances from measurement capability and observed process behaviour.
• Approve and explain every exceptional adjustment.
• Use a recognised claims method before converting mass balance into a market claim.