The Challenge

Buildings account for 39% of global carbon emissions, with operational emissions related to heating, cooling, and power use contributing 28%, and embodied carbon—emissions from materials and construction—making up 11% (World Green Building Council, 2025). Concrete alone is estimated to be responsible for approximately 6 to 8% of global CO₂ emissions (World Economic Forum, 2024). This high carbon footprint arises mainly from the energy-intensive process of heating limestone at extreme temperatures during cement production, to make clinker, which is a primary ingredient in concrete.

The built environment consumes about 50% of all extracted raw materials globally, emphasizing its significant resource demands (European Commission, 2018). Concrete is the second most used material on earth, following only water in volume of use (World Cement Association, n.d.).

Without the adoption of sustainable practices, the global consumption of raw materials for construction is projected to double by 2060, causing further environmental degradation and resource depletion (OECD, 2019).

A Circular Solution

Holcim, a worldwide leader in building materials, partnered with Seqens - a major social housing organization in France - to give birth to Recygénie, the world's first building fully made from recycled concrete. This 220-unit social housing complex utilised Holcim's ECOCycle technology, which turns construction and demolition waste into new building materials (Holcim, n.d.).

In 2021, a group of 1960s apartment buildings were torn down just outside of Paris, France. On the same site, construction began on the Recygénie complex, one year utilising demolition waste from the very buildings that once stood on the site (Fast Company, 2024). This project demonstrated Holcim's ECOCycle technology platform, which enables the production of concrete from 100% recycled construction and demolition materials. The platform includes advanced crushing and processing systems that transform demolition waste into high-quality recycled aggregates, sand, and cement components. By reusing these recycled materials, ECOCycle reduces reliance on virgin raw inputs, conserves natural resources, and contributes to lowering the carbon footprint of new buildings (Holcim, 2025; Holcim, 2023).

A key collaborator on the project was the CSTB (Centre Scientifique et Technique du Bâtiment), the French national organization for R&D in construction. The CSTB’s partnership was essential to monitor and validate the performance of the recycled material, as the project went beyond existing French building standards. By working with the CSTB to validate the material, the project helped create a pathway for future circular projects and challenged existing regulations that limit the use of recycled content.

The circular opportunity presented by Recygénie shows that big buildings can be constructed using only recycled materials, without a compromise on quality and safety. This helps keep waste out of landfills and encourages better use of resources. It sets an example in the field of sustainable building practices that can be used around the world (Holcim, 2023).

Climate Impact

Recygénie has significantly reduced its environmental impact. The project's primary CO₂ savings come from using recycled materials to create new clinker, a process that avoids the high-temperature calcination of virgin limestone—the main source of cement's emissions. The project also diverted over 6,000 tons of construction and demolition waste from landfills and saved an equivalent amount of natural resources by recycling materials such as cement, aggregates, and water. These efforts demonstrate the potential of circular construction practices to lower carbon emissions, reduce waste, and conserve resources (Holcim, 2023).

Replicability

The success of Recygénie proves that fully recycled concrete buildings are feasible and scalable. Holcim is replicating this model across the markets where it operates, adapting the solution to local building norms and material availability. In 2023, Holcim has recycled nearly 8.4 million tons of construction demolition materials (Holcim, 2023).

Several Irish companies are making great strides in the use of recycled cement and sustainable construction practices:

• Ecocem Ireland is a leading sustainable cement producer specializing in Ground Granulated Blast Furnace Slag (GGBS), a byproduct of the steel industry used as a low-carbon substitute for Portland cement. Their product significantly reduces embodied carbon in concrete while maintaining high performance. 

  
  

• Techrete are Ireland’s largest architectural precast concrete façade specialist, Techrete has launched a sustainable concrete range with a 50% reduction in embodied carbon, driven by incorporating cement replacement materials and high-performance mixes.

  
  

• Trinity College Dublin & FLI Precast Solutions developed a groundbreaking low-carbon concrete using biomass ash, an industrial byproduct from Edenderry Power Station, reducing carbon emissions by over 50%.

  
  

• Kilsaran, a longstanding Irish concrete products producer, implemented CarbonCure technology, which injects recycled CO₂ into concrete to permanently mineralize it for a reduced carbon footprint.