Sizewell C signs pledge to phase out diesel and high-carbon materials

Sizewell C has put its contractors on notice: prepare for life after diesel and a squeeze on the most carbon-intensive building materials. The nuclear developer has signed the Construction Leadership Council's Five Client Carbon Commitments, a pledge that pushes construction emissions down through buying decisions, contract incentives and cleaner site operations.

The move puts plant fleets, concrete mixes and steel sourcing firmly in the spotlight across the project's supply chain. Under the CLC framework, clients set dates for bringing carbon performance into contract awards, phasing out fossil fuels and eliminating the highest-carbon concrete and steel products. Sizewell C has yet to reveal its specific deadlines or material carbon limits.

For firms chasing work on the Suffolk nuclear project, the direction is clear. Carbon-cutting proposals will carry more weight, and suppliers will need to demonstrate the credentials of their products.

What could change on the ground?

The practical measures could include:

• Carbon reduction incentives written into new contracts
• Plans to replace fossil-fuelled site plant
• Lower-carbon concrete mixes and steel supplies
• Product emissions data to back up suppliers' claims
• Carbon management aligned with the PAS 2080 standard

The exact obligations will depend on Sizewell C's contract requirements. PAS 2080 is the UK's standard for managing carbon across the whole lifecycle of infrastructure, from design through procurement to construction.

Chief operating officer Bertrand Michoud said: "Through the Five Client Carbon Commitments, Sizewell C is committing to practical actions that will reduce emissions across our project and supply chain, from low-carbon procurement and materials to a future without diesel-powered construction activities."

The project has already started cutting carbon in its supply chain. It has struck a deal to reuse more than 15,000 tonnes of demolished concrete from neighbouring Sizewell A as material beneath foundation platforms — roughly the weight of two Eiffel Towers — cutting demand for fresh aggregate.

Does low carbon mean higher cost?

CLC net zero and biodiversity industry sponsor Matt Palmer argues the opposite. He said the shift could help keep costs down.

"There is a misplaced assumption that low carbon construction means more cost, but the Five Client Carbon Commitments are helping the sector deliver efficiently and innovation is driving down low carbon costs," Palmer said.

That argument matters for a project of Sizewell C's scale, where concrete and steel volumes are enormous and every saving in material or fuel compounds across the build.

The unanswered question is timing. Until Sizewell C publishes its deadlines and material carbon limits, contractors know the destination but not the schedule — and bidders will be watching closely for when carbon performance formally enters contract awards.