Costain: Advancing sustainable infrastructure

If critical infrastructure forms the physical foundation of the UK’s journey to net zero, then Costain is operating at its very core. As a major UK contractor and infrastructure solutions provider, the FTSE 250 index constituent plays a central role in delivering and modernising national infrastructure across a diverse range of sectors, including transport, water, energy and defence.

Costain attained the Green Economy Mark in 2024, supported by its role in delivering and upgrading infrastructure in areas such as water and rail, which are classified as green under the LSEG Green Revenues Classification System. In 2026, over half of Costain’s revenues are defined as green under the GRCS, with the greatest contributions coming from its water and rail activities [Note1]. These include work to strengthen water resilience and resource efficiency, alongside the delivery and upgrading of rail infrastructure that enables lower emission transport.

The Green Economy Mark is particularly helpful at a time when environmental credentials are of growing importance. It demonstrates how environmental outcomes have become increasingly relevant to Costain’s long-term commercial success, with profit and purpose reinforcing one another.

Costain is heavily engaged in delivering infrastructure that underpins the UK’s national decarbonisation and resilience priorities. In transport, it is part of the Skanska Costain STRABAG Joint Venture, delivering high-speed rail infrastructure, connecting regions across the UK and encouraging a shift away from higher emitting forms of transport. Costain is also delivering mechanical and electrical systems and high-voltage power supply infrastructure for new rail networks.

In water, Costain is delivering major infrastructure upgrades that support efficient water management and long-term security of supply. For example, Costain is part of an alliance delivering hundreds of kilometres of new pipeline for Anglian Water, helping secure the East of England’s water supply amid growing climate and population pressures.

In low-carbon power generation, Costain is playing a key role in several pioneering projects that are central to the UK’s net zero ambitions. These include the design and delivery of the UK’s first highly enriched nuclear fuel facility, commissioned by Urenco; [Note2] constructing pipeline infrastructure for the UK’s first carbon capture and storage project on Teesside; [Note3] and designing a hydrogen storage facility in Cheshire. [Note4]

Through the Green Economy Mark, Costain is able to clearly demonstrate its role within the UK’s growing green economy, which is increasingly important when competing for contracts.

For Costain, the transformation of national infrastructure is central to its growth strategy. [Note5] Through engineering, construction and consulting, Costain’s strategy focuses on delivering infrastructure that improves resilience, supports decarbonisation and enhances prosperity. [Note6]

Costain’s sustainability programme is built around three pillars: safeguarding the planet’s future, being a responsible business, and being a trusted employer and community partner. The company emphasises that sustainability is not simply an add-on to the business but is operationalised and embedded throughout. Alongside delivering green infrastructure for its customers, Costain is reducing emissions across its own operations. The company has committed to reaching net zero in its Scope 1 and 2 emissions by 2035, with a longer-term ambition to address Scope 3 emissions by 2045. [Note7]

As part of Costain’s decarbonisation plan, [Note8] the company has achieved verification to the PAS 2080 standard, which provides a recognised framework for managing and reducing carbon across infrastructure projects. Costain also prioritises reducing carbon emissions from energy usage, including reducing reliance on diesel across its operations and projects.

Costain places strong emphasis on collaborating with its suppliers. The company’s Supply Chain Academy supports small and medium-sized enterprises with free training on carbon management. 

Notably, Costain is working with partners on HS2 tunnels to replace conventional concrete with a lower carbon alternative, made from clay excavated during tunnelling. This clay is calcined, or heated, to produce a cement substitute, significantly reducing the carbon footprint of tunnel construction and demonstrating potential for wider industry adoption. 

As the UK continues to invest in more resilient, lower-carbon infrastructure, Costain is aligning engineering expertise with environmental outcomes and long-term commercial success. Recognised through the Green Economy Mark, the company demonstrates how commercial performance and environmental impact can align through the delivery of infrastructure that supports emissions reduction, climate resilience and economic growth.