Department of Architecture

Hiilipuisto - Carbon Park

Hiilipuisto project launches scientific monitoring of biochar-based soils in Jätkäsaari’s Hyväntoivonpuisto park, located in Helsinki centre. The project area consists of eighty urban trees which are planted on nine different soils, from which seven contain biochar. These soils were supplied by different Finnish soil producers and they are all commercially available. In addition to scientific research, the project contributes to creating new and developing current biochar practices in the green building sector.

Hiilipuisto project is organized by Aalto University (project lead), University of Helsinki, HAMK Häme University of Applied Sciences and The City of Helsinki. The steering group and project partners include central actors of the Finnish green building and gardening sector. The project duration is 9/2020-9/2021.
Kuva: Esko Salo
Hyväntoivonpuisto research area, photo credit: Esko Salo

Biochar-based soil contributes to carbon sequestration

Biochar has a twofold effect on the soil. First of all, applying biochar-based planting soils increases the carbon content of the soil since biochar itself is long-term carbon storage. Second, adding biochar to the soil accelerates the carbon sequestration of green areas by improving the growth and well-being of trees, especially in extreme conditions such as drought, and easing their maintenance. Even though biochar and its applications have been found to offer several promising results biochar is currently not applied widely nor it is considered in the industry guidelines such as standardized green building practices.

In Sweden, the City of Stockholm has been using biochar-based planting soils widely in the urban tree plantations already since 2009. Inspired by the example of the City of Stockholm, several cities and municipalities across Finland have already started to use biochar-based soils for experimental purposes. During the last few years, several smaller areas have been built on biochar-based soils. However, these experiments have not been documented nor followed-up and therefore they do not provide the type of information which is needed to make conclusions to develop green building practices which would enable widespread use and application of biochar. Hiilipuisto -projects scientifically documented and organized follow-up process contributes especially to this issue.

Hyväntoivonpuisto Park – Jätkäsaari

Hyväntoivonpuisto Park is located in Helsinki's new residential area Jätkäsaari which will be around a hundred hectares and it will be fully ready by 2030. Hyväntoivonpuisto Park is the most significant green area in the location, being one kilometre in length and just below one hundred meters wide it is also going to be the most important thoroughfare in the location.

Hiilipuisto -project area is located on a small part in Hyväntoivonpuisto Park between the streets called Hyväntoivonkatu and Malagankatu. The research done in this location aims to investigate how adding biochar impacts the well-being of the soil and the growth of the trees. Scientists are going to visit the park few times a year to take measurements from the trees and soil samples and analyse the impact of biochar based-soils in terms of water moisture content, carbon content and nutrient measurements. The research covers eighty trees and there is an information sign to inform locals about the project.

Hyväntoivonpuiston tutkimusalue kartalla

Hiilipuisto -projects research area is located between Hyväntoivonkatu and Malagankatu

Location on the map

What has been done so far?

(updated 12/10/2020)


  • Autumn: Soil samples and tree measurements
  • Spring: Trees were planted to the soil and their individual condition were analyzed and documented. Soil samples were taken.


  • Autumn: All planting soils were placed before winter, the trees were not yet planted. 

Project management

  • Professor, Ranja Hautamäki, Aalto-University, Department of Architecture
  • University Lecturer, Docent, Priit Tammeorg, University of Helsinki, Department of Agricultural Sciences
  • Principal Research Scientist, Outi Tahvonen, Häme University of Applied Sciences, Built Environment
  • Project Manager, Petra Rantalainen, City of Helsinki
Projektin partnerit
Hiilipuisto -hankkeen partnerit

Project has been funded by Maiju ja Yrjö Rikalan Puutarhasäätiö

Helsinki Biochar Project

The city of Helsinki aims for carbon sequestration and thriving urban vegetation by increasing the use of biochar. The project promoted circular economy as biochar was experimentally manufactured from the city's own waste materials and tested on several public park pilot sites.

Helsingin biohiilihanke jatkaa Hiilipuiston jalanjäljissä
A concptual cycle of the experimental process of the Helsinki Biochar Project
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