How cities can create market opportunities for net zero

Cities are emerging as critical players in delivering scalable decarbonisation solutions and their role was underlined by a keynote address from Labour Peer and former Bristol mayor Marvin Rees at Carbon Crunch 2025 in London. According to Marvin, city regions can also unlock transformative investment in low-carbon infrastructure through strategic urban governance and public-private partnerships.

“Actual change happens in real places like Bristol, Sheffield, Birmingham, London, Cardiff and Glasgow,” said Marvin Rees in his opening keynote speech at Carbon Crunch 2025 in London.

As Bristol’s former mayor, Marvin, who has now taken up a seat in the House of Lords as Baron Rees of Easton, is well placed to share his experience of local government and how he was able to make a significant and lasting legacy on decarbonisation during his tenure.

“I could not work for the good of the people in my city simply by working inside the city boundaries with a pelican crossing here and a pothole there,” he explained “City leaders have to shape the national and international context in which we work and must address the very nature of the global challenges that impact on us today.”

When Marvin was first elected, he said he had no idea just how important it would be as a mayor of a UK city to influence the world and didn’t appreciate just how influential a city leader could be.

Connected challenges

“The challenges and opportunities we face now cross-national boundaries,” he explained. “The world’s population is so mobile now… and we are interdependent; we are globally dependent and yet we have an international government structure that works as though we're independent of each other's interests.”

Marvin said there was a need for global governance to move into the next iteration with the leaders of cities and networks of cities as equal partners, shaping national and international policy.

"I started to attend and participate in a number of city networks including the Global Parliament of Mayors, or which I became co-chair, Eurocities and C40, which is a global network of nearly 100 mayors who are united in action to confront the climate crisis. In these conversations we would affirm the importance of city leadership and share best practice, but I would sometimes get frustrated,” explained Marvin.

“We need to start talking about money, because when a mayor tells me about best practice, whatever it is, think housing, community development, a transport solution, a climate intervention, my first question is, ‘great, how much did that cost?’ Because we'd all be doing best practice if we could afford it.”

This is where the disconnect is. He added: “City leaders must have access to adequate and appropriate finance if they are going to deliver for their populations, countries and the planet. It is a relevant and live conversation. We need national governments and global institutions to catch up quickly. The finance must be in place but there is more.

“For meaningful action, we can't just have cities in the room talking with people with money. We also need engineers in the room, because they know what the actual solutions are that need to be paid for and deployed.”

It is these factors that Marvin believes are the best combination to bring about real change. “We need to bring together three things – the places where people live, the technology and the finance to transform cities.” Marvin did just that with Bristol City Leap and believes it is a model that could be replicated around the UK, as well as globally.

For meaningful action, we can't just have cities in the room talking with people with money. We also need engineers in the room, because they know what the actual solutions are that need to be paid for and deployed.

Bristol City Leap

Bristol City Leap is a partnership between Bristol City Council and energy solutions provider Ameresco UK which is accelerating green energy investment in the city as part of its journey to decarbonisation and carbon neutrality.

“We were looking at something that would really make the investors leap into our relationship with energy,” explained Marvin. “We asked ourselves; how could we transform the cities system? My deputy mayor Craig Cheney explained we needed to solve financial challenge and, if we could do that, we would make the projects we needed to get the technology rolled out bankable.”

Bristol City Leap is set to invest nearly £500M over five years and £1bn over its 20-year life to transform the city’s energy landscape. This ambitious programme will fund the rollout of low-carbon technologies – including solar power, wind energy, heat networks, heat pumps and energy efficiency upgrades – driving Bristol towards its goal of becoming carbon neutral by 2030. It includes £60M of social value including local jobs, a commitment to the local supply chain and a community energy fund.

“We bundled together our public estate, including public buildings, our council house stock and the heat network we had,” explained Marvin. “We said to the market, if we gave you this for 20 years to innovate and develop and you come in and deploy your tech to reduce our emissions, deliver social value and work out how you get your return, would you be interested?”

The council received over 180 expressions of interest.

“We were surprised at the level of interest but took it as evidence that if we can get our acts together, cities can create the conditions that motivate markets to move,” said Marvin. “The partnership is a great example of what can happen if we help cities get to the point where they can be a bankable partner for the private sector.”

Ameresco UK senior vice president Mark Apsey, speaking later at the event in a panel discussion, agreed with Marvin: “We need cities that are motivated and want to create a better city environment for their citizens. It works in Bristol because the partnership is outcome based, we are not saying what is the cheapest way to put solar on this roof, it is about carbon savings over time and we have committed to over 140,000t of carbon savings over the next five years.”

Alongside carbon saving targets, the partnership also set targets around social value and using the local supply chain.

Mark explained: “Crucially alongside all those great projects, it is also an investment in social value and, specifically, local spend. This is £60M of social value invested in Bristol in the first five years and over £50M in local businesses working the local supply chain, with 400 jobs created in the Bristol area and 1,000 regionally, all delivering real benefits to the city.”

But Mark also warned other cities looking to replicate the Bristol City Leap would need to focus on the cost of procurement. Nonetheless, the programme effectively brought together the city with financiers and engineers to deliver real change.

Moving forward

The key message that the infrastructure and built environment sector should take away from Marvin’s address is that when considering current assets and associated challenges, the factors that would enable the market to move to solve them. Cities, councils, landowners, investors, engineers, and construction partners all have a role to play and must collaborate to unify interests and bring about action faster.