All facilities on the contract are now either fully completed or in the post-completion warranty period under the terms of the contract, during which some further work and plant modifications will be completed.

In a trading statement this morning, Costain said the handover released contractual retention and milestone payments of £14m.

Its Natural Resources Division reported a £5m loss last year due to provisions on the job and Costain also reiterated it would no longer pursue fixed price contracts of this type.

At the end of last-year Costain’s subcontractor TEG fell into administration because of cashflow problems relating to withheld retentions on the project.

Alleged design faults had delayed completion of the facilities which are due to handle 175,000 tonnes per annum of green and food waste.

Costain said that several large-scale energy, water and transportation framework wins have lifted the year-end order book to a new record level of £3.5bn, £500m ahead of 2013.

Costain said it also transferred two PFI assets into the group pension fund for £7.4m representing a discount of 7% and realising book profits of £3.7m.