Bio-waste and sewage sludge to be used in low-emission concrete production in Mäntsälä
Carbon dioxide generated from bio-waste will soon replace cement—a major source of emissions—in concrete production at a plant in Mäntsälä, Finland, Yle Uutiset reports.
Starting next winter, the Mäntsälä biogas plant will capture biogenic carbon dioxide and supply it to concrete factories in Joensuu and Hollola. The CO₂ will be chemically bound into concrete, reducing the need for traditional cement, which accounts for a significant share of the construction industry’s emissions.
The project marks the first time in Finland that CO₂ derived from biomass will be used commercially in concrete production. The technology, developed by Finnish company Carbonaide, was piloted in Hollola in 2023, where CO₂ replaced up to 20 percent of the cement in products like paving stones.
The Mäntsälä plant currently processes bio-waste from stores and sludge from wastewater treatment, producing biogas and fertiliser. Until now, the CO₂ released in the process has been vented into the atmosphere. Once operational, the new system will capture 3,500 tons of CO₂ annually—equivalent to the yearly emissions of nearly 2,000 passenger cars. When used to replace cement, the climate benefit effectively doubles, as cement production itself is highly emissions-intensive.
Economic challenges remain
While the environmental benefits are clear, cost remains a hurdle. Cement currently costs around €150 per ton, while CO₂—whether fossil or biogenic—runs closer to €200 per ton. However, Carbonaide’s operations director Jonne Hirvonen expects biogenic CO₂ prices to fall as production scales up and processes become more efficient. Meanwhile, cement prices may rise due to stricter emissions regulations and global supply chain disruptions.
The Mäntsälä plant’s CO₂ output is modest compared to industrial sources like pulp mills, which emit millions of tons annually. Yet experts see potential in scaling the model. “When these examples multiply, we can start talking about quantities significant for Finland’s climate goals,” said Lauri Kujanpää, research team leader at VTT Technical Research Centre.
Beyond concrete, captured biogas CO₂ could also be used in greenhouses or food production. The Mäntsälä project demonstrates how small-scale circular economy solutions—like recycling bio-waste—can contribute to broader climate efforts.