What it takes to deliver low-carbon infrastructure in practice: Lessons from Lower Thames Crossing

Infrastructure has a central role in enabling economic growth and improving connectivity. At the same time, the way infrastructure is delivered must continue to evolve if the sector is to contribute meaningfully to the UK's low-carbon future.

For project professionals, the challenge is increasingly less about setting ambition and more about embedding it into the decisions and behaviours that influence delivery.

At the Lower Thames Crossing, reducing carbon is a core value rather than an environmental add-on. That means looking beyond operational outcomes and addressing the carbon associated with construction itself.

As a carbon pathfinder project, the Lower Thames Crossing has set an ambition to be carbon neutral in construction by reducing construction emissions by 70% against baseline levels and responsibly offsetting residual emissions that cannot be eliminated.

Delivering this ambition requires more than isolated low-carbon initiatives. It means integrating carbon reduction into procurement, design, materials, delivery and capability so that every part of the programme moves in the same direction.

Putting carbon at the heart of infrastructure procurement

One of the clearest examples is the procurement process.

The Lower Thames Crossing placed carbon at the heart of contracting, enabling competition between bidders to secure further carbon reductions at no extra cost. It also became the first major UK infrastructure project to include a legally binding construction carbon limit within its planning application.

This approach has already delivered significant reductions against the baseline while reinforcing the role clients can play in shaping market behaviour.

Moving away from fossil fuels in construction

The programme has also prioritised interventions in the areas with the greatest carbon impact.

One of these is fossil fuels. The Lower Thames Crossing is committed to eliminating diesel from its worksites through investment in alternative technologies, including procuring the largest volume of green hydrogen ever produced for a British construction project. This supply of 2,500 tonnes of hydrogen is enough to replace more than 12 million litres of diesel and save around 30,000 tonnes of CO₂ emissions. Alongside this, the programme is expanding the use of zero-emission plant and equipment where operationally viable, demonstrating how construction can transition away from fossil fuel dependence.

Designing and building for low-carbon infrastructure

Low-carbon materials and design have also been prioritised.

Where cement cannot be eliminated or substituted, the objective is to use the lowest-carbon product available within the most efficient design. The programme is also maximising opportunities to reuse and recycle steel across temporary and permanent works while exploring alternatives where appropriate.

A programme-wide approach to reducing carbon through design has been central to the Lower Thames Crossing as it has challenged conventional engineering, construction methods and materials to reduce embodied carbon before construction begins. One example is the decision to use a single tunnel boring machine to excavate both tunnel bores rather than deploying two simultaneously, reducing carbon and cost without extending the programme. This is also reflected in the programme's low-carbon footbridge design competition, where the winning concept eliminated concrete from both the bridge and its approach ramps while integrating planting into the design to promote habitat connectivity. Together, these examples show how early design decisions can deliver substantial carbon savings.

Building supply chain capability for low-carbon construction

Alongside technical interventions, capability and governance remain essential.

The Lower Thames Crossing became the first road scheme to achieve PAS 2080 accreditation, reinforcing a structured approach to carbon management. Internally, Carbon Literacy training has strengthened capability so carbon considerations are better understood and reflected in day-to-day decisions. The project is the first major UK infrastructure project to be awarded Gold by the Carbon Literacy Project after making it a tender requirement for all three Delivery Partners to achieve Silver Carbon Literate Organisation status within 52 weeks of contract award; another UK infrastructure first.

Why clients must lead the transition to low-carbon construction

Importantly, this work is not happening in isolation.

The Lower Thames Crossing was one of the first organisations to sign the Construction Leadership Council's Five Client Carbon Commitments (5CCCs).

Developed through the CO2nstructZero programme, the commitments recognise that clients have one of the strongest levers to accelerate decarbonisation. Through procurement, specifications, investment decisions and delivery expectations, clients influence what becomes normal practice across the supply chain. Collectively, signatories to the 5CCCs are responsible for more than £30 billion of UK construction investment, around 13% of the UK construction market, demonstrating the scale of client influence in accelerating the transition to low-carbon construction.

The commitments focus on practical action: procuring for low-carbon construction, setting phase-out dates for fossil fuels, reducing reliance on the most carbon-intensive concrete and steel products, and adopting PAS 2080 as a common approach to carbon management.

For the Lower Thames Crossing, the commitments align ambition with delivery.

Many of the actions underway directly support these commitments, including contracting for carbon, reducing diesel dependency and embedding carbon requirements into project governance and delivery decisions.

Collaboration across the supply chain drives lasting change

Reducing carbon at the required scale cannot be achieved by clients acting alone; it depends on bringing the supply chain on the journey. At the Lower Thames Crossing, collaboration with delivery partners, suppliers and manufacturers has been central to turning carbon ambition into practical delivery. Alongside embedding carbon requirements within procurement and contracts, the programme has invested in building capability across the supply chain through initiatives such as the Supply Chain Sustainability School, helping develop the skills needed to deliver lower-carbon infrastructure. It has also convened suppliers across steel, concrete and earthworks to explore further carbon reductions, share innovation and tackle common challenges. By creating the conditions for collaboration rather than simply setting expectations, the programme is helping build supply chain capability and confidence that will support low-carbon delivery long after the project is complete.

What project professionals can learn from the Lower Thames Crossing

For project professionals, there is a wider lesson.

Delivering low-carbon infrastructure is not achieved through a single innovation or one successful pilot. Progress comes from creating conditions where better decisions become easier to make repeatedly throughout the project lifecycle.

That requires clear targets, commercial mechanisms, capability, collaboration and a willingness to challenge established approaches.

The Lower Thames Crossing continues to explore what that looks like in practice and, importantly, how those lessons can contribute beyond a single programme.