Helsinki Biochar Project

In an undergoing renovation, the Siltamäki sports park will have five new sports turfs with a high-class growing medium. The soils consist of 90vol-% sand and 10% peat. In a single pitch with a 810 m² surface area, the peat in the topmost 15 cm layer is partly but at minimum with 5%, replaced with biochar. This will result to the site containing an estimated 20m³ of biochar. The turf will be made from ready lawn, and the construction is scheduled to be completed in spring 2023. 

A new kind of dynamic perennial planting is being constructed in Kalasatama. The site is located in Työpajanpiha, in front of the house of the Helsinki Urban Environmental Division (KYMP). There are two plant community types that each will be receive biochar in their soils. Each experiment is also matched with a comparable replicate area with no biochar but same plants. The plant communities are composed using principles inspired by a naturalistic planting design. The biochar will be enriched in advance with nutrients by mixing it with compost in 1:1 ratio. The final volume of biochar in the substrate is 20%. The construction is expected in July 2023.

A new tram route is being built in Kruunuvuori and in order to increase water infiltration, many stretches are covered with hollow bricks. The brick intervals are filled with soil and sown with a grass mixture. As the depth of the soil is only 12 cm with gravel underneath, the growth environment is very dry. To improve the drought resilience and water availability, the soil is amended with 10% biochar. The biochar part of the project is expected to happen in July-August 2023

Located between the city library Oodi and the Musiikkitalo concert house, Tapahtumapuisto park includes vast lawns that are highly exposed and in intensive use. The same is valid for park lawns in Kaivopuisto park. The aim is to incorporate 3% biochar into the lawn soil and obtain better drought resilience and nutrient retention.

The application will be conducted together with the annual aeration procedure and the work is realized using the Turf Gamechanger machinery. The lawn is perforated and biochar is inserted into the holes together with fertiliser and a microbial inoculant. UPDATE: The application was realized during the 3rd of May, in the Tapahtumapuisto- and Makasiinipuisto parks. Changes were made to the original plan and they will be reported later. The application is planned to be repeated in the summer.

As the Vaasanpuistikko square, located above the Sörnäinen metro station, is undergoing massive renovation, five oak trees planted in the 1980's will remain in place. In order to improve their growth, three trees will have their growing medium changed to structural soil instead of the current, compacted soil. The structural soil matrix is designed to carry the heavy load of the square, and hence it consists mainly of 50-150mm stones. To improve the moisture and nutrient conditions, it will be amended with nutrient-enriched biochar which is flushed down in the cavities using water. The construction is scheduled to start in June 2023.

In line with the carbon neutrality targets, Helsinki is piloting sites where construction of infrastructure is aimed to be realized with net zero emissions. The second pilot is situated in Herttoniemi where the "itäbaana" bike street is being expanded. The park design includes planting approximately 70 new tree individuals. Further, the current plan is to select 46 trees that will receive 10% of biochar in their growing medium. The biochar for this site will be manufactured and donated by GRK, an infrastructure constructor company with its own ambitious climate targets. The biochar plantings will begin in early May 2023.