Renaturing the roofscape of Metropolitan Barcelona: Join the TOP SEC’s journey!

Climate change, urban heat islands, resource scarcity and biodiversity loss are pressing issues that demand bold, innovative solutions. Cities are drivers of this multi-crisis which calls for rethinking how they redesign and build urban environments. That’s where TOP SEC comes in —  a cutting-edge project aiming to transform rooftops in Metropolitan Barcelona into vibrant, self-sustaining and nature-positive green spaces.

Led by the Area Metropolitana Barcelona (AMB) and co-funded by the European Urban Initiative, TOP SEC is pioneering a new model of ecological green roofs. Gravel rooftops - just like the one at a typical school in AMB, shown in the picture above - will be transformed through planting native species that will thrive without irrigation, making them an ideal solution for water-scarce Mediterranean cities. Even more exciting? They’ll be developed using locally sourced materials — including biochar obtained as a byproduct of municipal organic waste — turning them into a valuable resource for nature.

Cities today face a range of socio-environmental challenges, from rising temperatures to poor air quality and increasing flood risks. The proposed roofs can be a game-changer by:

• Reducing urban heat islands – Natural roofs absorb heat, cooling buildings and making cities more liveable.
• Improving air and water quality – Plants filter pollutants from the air, and the substrate retains rainwater, easing pressure on drainage systems.
• Enhancing biodiversity – These rooftops will provide peaceful new habitats for endemic flora, birds, pollinators, and other wildlife.
• Boosting energy efficiency – By insulating buildings, they reduce the need for heating in winter and cooling in summer.
• Supporting circular economy – Organic waste that would otherwise go to landfills is transformed into biochar, a key component of the green roof substrate.
• Enhancing mitigation – Biochar and the roofs’ vegetation will act as new carbon sinks within the city

Roofs are quiet spaces, which are very difficult to find in cities like Barcelona due to human pressures. Such quiet spaces attract birds – for this reason TOP SEC wants to maintain these roofs quiet for their priority users.

In addition, in contrast to compost which cannot be used locally in significant amounts due to the lower demand, biochar production is more scalable and has higher demand locally. Therefore, this new solution, enables short supply chains which further reduce emissions.

TOP SEC isn’t just about managing waste and making cities more biodiverse. It’s about engaging communities in the process. By co-creating with local residents, businesses, schools, the construction industry and social housing tenants, the project will ensure that the regenerated roofs serve not just the environment but also the communities that implement them.

The ambition is that this integrated solution will be upscaled in the city beyond the project’s lifecycle but also be reproduced in other cities across the EU and beyond.

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Project Partners at the kick-off meeting, February 2025

TOP SEC brings together 12 partners from across Europe, including:

• Local authorities like the Area Metropolitana Barcelona - including IMPSOL as the AMB’s Institute for Land and Asset Management - and Cornellà de Llobregat to test the solution, as well as Rome, Toulouse, and Petroupoli to become early adopters
• Academia and research institutions like the University of Lleida and The Catalonia Institute of Construction Technology
• Industry and SMEs such as Ingelia, Bruc Jardí, and ASESCUVE (Spanish Association of Green Roofs)
• Civil society and urban ecology experts including Cíclica

With expertise ranging from urban planning, agronomy, botanology to construction, waste management, and community engagement, this partnership is set to push the boundaries of sustainable urban development.

Over the next 42 months, TOP SEC will:

• Pilot the new green roof model in 5 diverse locations in Metropolitan Barcelona
• Test innovative materials and circular economy approaches.
• Engage local communities in co-creation workshops.
• Measure real-world impact to inform future urban policies.
• Transfer the solution to three European Cities

Whether you are an interested citizen, an urban practitioner or a policy maker, we want you to be part of this journey. Follow our updates, join our community events, and see firsthand how ecological rooftops can become engines of urban transformation.

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