One of the first municipalities in Denmark is investigating the potential of biochar to reduce CO₂ emissions and improve the urban environment with an EU-funded experiment.
The Danish municipality of Vallensbæk is taking an innovative step in its climate policy with a pilot project testing the use of biochar in urban greenery. The goal? Reduced water and maintenance costs and a contribution to the municipality's climate goals by long-term sequestration of CO₂ in the soil. The experiment is part of the EU project Power Bio and consists of 24 test beds along two streets in the municipality. Half of the beds are enriched with certified biochar, while the other half serve as control beds. The research should demonstrate to what extent biochar can contribute to sustainable urban greenery.
What is biochar?
Biochar is a product of pyrolysis, a process in which biomass is heated at high temperatures and without oxygen. The material is known for its ability to retain water and nutrients in the soil and to store CO₂ for up to hundreds of years. Vallensbæk hopes that this specific application of biochar will not only help with climate action, but also contribute to more efficient resource use and increase the survival of plants during dry periods.
June Thomsen, Climate Coordinator at Vallensbæk, explains: “Like many other municipalities, Vallensbæk has ambitious climate goals that we are continuously working towards. Biochar could be an important tool in our efforts to reduce CO₂ emissions. We hope that our experience with this pilot will show how we can create green spaces that both contribute to our climate goals and use resources more efficiently.”
Part of a broader EU initiative
The Vallensbæk experiment is part of the Power Bio project, which is working with 23 other municipalities, companies and research institutions to develop innovative, green methods for processing biomass, such as grass and washed-up seaweed. Luna Naja Rosendal Katz, project leader at Gate 21, emphasises: “Vallensbæk is at the forefront of testing biochar in Denmark. The results will provide insight into the impact on maintenance costs, climate and plant growth. We look forward to seeing if this model can be scaled up to other municipalities in Denmark and Sweden.”
How does the test work?
To achieve measurable results, Vallensbæk has installed 24 raised planting beds made of corten steel. Half contain a mix of biochar, gravel and topsoil, while the other half serves as a control. The beds are positioned to experience equal amounts of sun, rain and drought. This makes it possible to accurately measure differences in water requirements, growth and maintenance between the beds. Engineering consultancy Sweco is monitoring the experiment. The results can be used to develop a business case for applying biochar in future green infrastructure projects.
Source and photo: Vallensbaek.dk
