Offshore decommissioning is ramping up across energy regions worldwide. In the UK, annual spend broke £2 billion for the first time in 2024, on track to reach £3 billion annually by the end of the decade. In Australia, costs are even steeper, estimated at up to AUD 60 billion over the next 30 to 50 years. And across the Middle East, ageing offshore assets are starting to raise the same challenge.
As activity scales, so does scrutiny of where cost and schedule risk build. Most of that scrutiny lands on offshore activity, such as well plugging and abandonment and subsea recovery. Once material leaves the asset, however, the risks shift towards waste handling, classification and onward treatment, with their own cost, schedule and compliance pressures.
Decommissioning waste streams are complex, often requiring specialist handling such as chemical treatment, radiological monitoring or controlled disposal routes. Few contractors hold licences across all of them, so unless a programme is deliberately consolidated, waste typically passes through several third parties.
I've seen programmes lose weeks here, usually because of friction at the handover between contractors rather than any single failure. That's why at ASCO we take responsibility for the full process from start to finish, with one team managing the sequence, interfaces and delivery.
I understand why spreading the work across several specialists can feel like the safer option, bringing in the right expertise while sharing the risk. But it can also spread responsibility, so it is worth looking more closely at what happens during those handovers and why problems emerge.
Where routine handovers fail
In theory, waste should follow one continuous journey even as responsibility transfers between contractors. In practice, it's rarely that straightforward. The required treatment route can change as material is inspected, sampled and characterised. It's common for the work scope to evolve during recovery operations, from changes in waste type or quantity to contamination that wasn't flagged at removal.
A fragmented supply chain only adds to this complexity, introducing interface risks that drive schedule overruns and liability disputes. We've traced these back to a handful of recurring issues:
- Incomplete information reaching the receiving facility before it accepts a waste stream
- Classification changing as sampling reveals more than was known during removal
- Assessments being repeated because the next contractor wasn't involved in the original classification
- Material sitting in temporary storage while documentation is clarified
Rarely is any single contractor at fault. Rather, it's down to the handoffs between them where the information gets lost, and the cost of routine issues adds up.
Where the paperwork falls behind
Often, the waste material is already moving through the process while the paperwork is still catching up. Regulations look different in each region, but the principle is the same: waste can only move to an authorised party, accompanied by an accurate description.
In the UK, the requirement is a waste transfer note, or for hazardous waste, a consignment note. In the UAE, similar obligations apply under integrated waste management law covering classification, transport and treatment. While in Australia, a tracking certificate is required both when waste leaves site and when it's received. Still, none of it confirms the original classification was correct.
Decommissioning involves inherent unknowns, since its typically impractical to fully characterise a waste until removal. Even with good intentions, an operator remains responsible for their initial waste characterisation and still have a duty of care for correct disposal further down the chain. Until the paperwork is corrected, the material remains non-compliant.
These delays don't just create compliance exposure, they more often than not impact programme timelines. Westwood Energy analysts estimate that in the UK alone delayed decommissioning projects could add a further £4.25 billion to industry costs beyond current forecasts. Contractor friction isn't the only cause, but it's one of the factors operators can influence directly.
One accountable partner, end to end
One way to reduce this exposure is to limit the number of parties involved in the waste chain. On a recent decommissioning scope for a major UK operator, covering an FPSO and its associated subsea infrastructure, ASCO took responsibility for the full onshore programme.
We delivered the produced water management, subsea infrastructure processing and specialist naturally occurring radioactive materials (NORM) treatment as one integrated scope across multiple UK locations. Our team controlled the sequence, interfaces and delivery from start to finish, giving the client a single point of accountability throughout.
We managed 2,400 tonnes of produced water and flushings from the Port of Teesside, in line with environmental regulations. At the Port of Blyth, we received 1,675 tonnes of subsea materials, including risers, umbilicals and concrete mattresses, across three vessel calls. NORM-contaminated materials were then transported to our own dedicated NORM processing facility in Aberdeen for decontamination prior to recycling, while NORM-free materials were recycled directly from the port.
Many of the factors that drive up decommissioning costs are difficult to control, from rig availability and weather windows to changing government policy. How the waste scope is structured, however, is a choice. The more organisations involved in handling decommissioned or waste materials, the more interfaces there are to manage and the greater the risk of delay, duplication and additional cost.
This is one of the few variables operators can act on directly, and getting it right protects both the schedule and the bottom line.
