Helsinki Biochar Project
Biochar to reach a climate- neutral city
The city of Helsinki has set an ambitious program to be carbon neutral by 2030, and all means necessary need to be taken to achieve that goal. Emissions are being cut throughout the city and to reach the target, 20 % of emissions, equalling to 702 kt CO2- eq., can be compensated. By 2040, the city will offset all remaining emissions through carbon sinks located within the city´s geographical boundaries, which is where biochar is needed
In addition to a means to sequester carbon, biochar has potential to play a role in climate adaptation strategies. Biochar can be added as a soil amendment changing the absorption capacity and structure of the soil. Increasing the capacity of urban soils to be more resilient to extreme weather events, such as storms and prolonged periods of drought, could potentially serve as one of multiple means for urban climate adaptation.
Waste materials collected from Helsinki to be used as feedstock for biochar
Three different feedstocks were collected specifically for the project's purposes in 2022 and pyrolysed in the HSY (Helsinki region environmental services authority) pilot plant in 2022-23. The HSY plant has been previously developed and tested for making sludge char and now HSY is open for testing other materials. The resulting biochar will be used in urban green structures around Helsinki in 2023. Other materials were also evaluated for processing, but not realized due to low availability, high gravel content and logistical and storage issues. These materials included e.g. autumnal street sweeping waste, dog droppings, human waste from public outhouses and meadow clippings with invasive spanish slugs.
Intended experimental sites in Helsinki
Currently, a number of sites that are currently being designed for construction have been selected to be amended with biochar. The list is evolving, and the plans are subject to change. The information in the list is constantly being updated. Pictures of the ongoing projects are uploaded on our instagram site.
In the Siltamäki sports park five new sports turfs with a high-class growing medium were constructed during summer in 2023. The growing medium consists of 90vol-% sand and 10% peat. One field acts as an experimental site and in July 2023, a layer of biochar was mixed into the topmost 12-15cm layer of the soil. This required 22m3 of biochar onto the 2925 m2 pitch and resulted in the top layer containing approximately 5% biochar. The turfgrass was established on site by sowing.
A new kind of dynamic perennial planting was 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 received biochar in their soils. The plant communities are composed using principles inspired by a naturalistic planting design. The biochar was either enriched in advance with nutrients by mixing it with compost in 1:1 ratio, or applied with compost without pre-charging. The final volume of biochar in the substrate is either 0, 7 or 20%. The construction has begun in August 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 and Makasiinipuisto park include vast lawns that are highly exposed and in intensive use. In order to obtain better drought resilience and nutrient retention, a small percentage of biochar (~1 l/m2) was incorporated into the lawn soil. The application was conducted together with an aeration procedure using the Turf Gamechanger machinery. The lawn was perforated, biochar was brushed into the holes and topped with fertiliser and a microbial inoculant.
The application rate of biochar was lower than intended and a remake was planned for the autumn. However this plan was rejected as the Urban Environment Division is mapping out the need for wider- scale renovations in the park area.
In september 2023, a different part of lawn was selected to serve as a test site for trying out a new method of lawn renovation with biochar. An area of 1500m2 was first handled with a uniscratcher machine to remove most of the dead turf layer. Thereafter, 8m3 of biochar was applied and rotavated into 15 cm depth. The soil was topped with turf soil mixture before resowing the grass seeds.
The Vaasanpuistikko square, located above the Sörnäinen metro station, is undergoing massive renovation. In the process, five oak trees planted in the 1980's remained in place. In order to improve their growth, three trees had their growing medium changed to structural soil instead of the old, compacted soil. The structural soil matrix was designed to carry the heavy load of the square, and hence it consists of a stony matrix. To improve the moisture and nutrient conditions, the space between stones is normally filled with soil. In this case the voids were filled with biochar. The renovation is still undergoing some fine-tuning to add nutrient components and water holding capacity.
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. Fourty six trees were selected to receive 10% of biochar in their growing medium. The biochar for this site was manufactured and donated by GRK, an infrastructure constructor company with its own ambitious climate targets. The biochar park was finished in October 2023 and first measurements on tree dimensions were made to enable annual future follow- up of how biochar effects the tree growth.
Four individual parking spots around Helsinki are being transformed into green islands. Coarse biochar which is pre-activated with compost will be used in the growing media to add water retention in the root zone of plants. A single spot in Eerikinkatu street will have approximately 2 m3 of HSY woodchip biochar in its growing medium. The site will be constructed in october 2023
In the Kalasatamasta Pasilaan (KaPa) project, long stretches of tram track are paved with similar hollow stones as in Kruunuvuori. On a specific area in Hermannin rantatie road, comparisons are made between 0, 5 and 10% addition of biochar and further comparing two different biochars. The biochars are pre-activated with compost, mixed at least 1 month in advance of construction. Whereas in Kruunuvuori the paving will grow grass and the growing medium is intended for park lawns, here it will have a mixture of flowering plants and a soil mixed from recycled sanding sand.
A new residential area will be built in Stansvikinkallio in the coming years. Many streets will have linden trees under paved surfaces and therefore the trees will get a structural soil around their roots. To find out what is the effect of biochar, as well as the effect of watering the trees with nutrient solution, an experimental setup has been planned.
A part of the trees will be planted in a soil recipe that complies with the conventional Stockholm planting soil. It consists of 75% stones, 12,5% of biochar and 12,5% of compost. Some of the trees will receive nutrients along with the watering regime for the first three years of growing as is done in Stockholm, and some will only have pure water, which is the current practice in Helsinki.
Additionally, three trees will be planted without biochar which is replaced by conventional soil for broad-leaved trees.
The schedule of construction is open and will be timed as the general planning of the area proceeds.
A playground yard in "Leikkipuisto Vähätupa" in the Konala residential area is undergoing a renovation. An old rock ash area is being converted into a flowering meadow by adding a thin 10 cm layer of soil and seeds on top. There is relatively little knowledge about how biochar acts in meadow plant communties and wether its effect in the long run will be beneficial or not. Hypotheses range from beneficial increase in microbial activity and controlling of excess nutrients into unwanted functionality as a long-term fertilizer agent. To gain insight on the effects, half of the meadow will receive 10% of uncharged, raw HSY woodchip biochar into the 10 cm soil layer and half will remain without. The construction is taking place in late october.
Helsinki city garden, managed by Stara construction services, conducted a light pot experiment aimed for comparing different biochars against each other. The experiment was realized in July-August and the results will be reported later on. The base growing medium itself is an experimental mixture that is being tested as an alternative for the regular peat-based medium that is normally used for bedding plants. It consisted of equal amounts of regular peat-moss substrate, the city's own compost and wood fiber provided by Novarbo Oy. Each treatment included 5% of biochar, including HSY biochars made from woodchips, lake reed, soft green waste, twig crush and ammonium-quenched sewage sludge. The preliminary results indicated a fairly equal growth with all biochars and an overall increase in root biomass in comparison to the conventional peat-based medium.
Citizen engagement in biochar related activities
Because biochar is still a relatively unknown material, the Helsinki Biochar Project aims to increase the awareness of citizens on the potential of biochar. In order to do so, the project strives to set up a series of trials in the Helsinki metropolitan area to demonstrate the various stages of the biochar cycle to citizens, ranging from showcasing the production of biochar from local waste streams, how it works as a means to sequester carbon and finding engaging ways to utilise the material as a climate adaptation tool. The goal of the Helsinki Biochar Project is to demonstrate that converting local waste streams into responses to climate change is not just a distant process for decision makers only, but can be an engaging capability-building activity for citizens as well.
The Jätkäsaari community garden is a mobile garden group consisting of around 15-20 gardeners. This gardening community makes use of the many derelict urban spaces in the local area waiting for development. Once development starts on the lot, the garden moves to a nearby available location. The concept arose from seeing opportunity for using derelict spaces in the neighborhood and because the initiators made use of a temporary lot at the Lapinlahden lähde garden from which they had to move.
The infrastructure of the garden community is adapted to these temporal situations. For example, the gardeners only make use of 1m2 garden boxes placed on pallets so they can easily be moved. Gardeners can rent rights for a garden box for 7,- a year. This arrangement was negotiated with the City of Helsinki with the help of Dodo, a local urban environmental association.
One mayor challenge for this community due to its need to be mobile is access to water: which is now tapped in the waste recycling room of a residential building located a couple hundred meters from the site. Another related challenge is water retention capability of the garden boxes: as they are positioned on top of pallets, the soils dry out easily. It is to be tested if biochar can play a role in reducing the irrigation needs of the Jätkäsaari community garden
The Lapinlahti garden community is located in the Lapinlahti bay area in Western Helsinki and is part of the pro-Lapinlahti mental health association, who rent the land from the City of Helsinki. The garden consists of two parts: a larger part where gardeners rent individual plots of various sizes, and a part that is collectively maintained by a group of gardeners.
The individual plot rental side of has a waiting list of interested farmers. Every year, if there are vacancies, new tenants are selected via a lottery system. Tenants of individual plots can also participate in voluntary group activities such as talkoots, a Whatsapp groups for discussions or collective purchasing of garden materials. Garden activities are coordinated by a small team. The communal side of the garden started as a means for people with mental challenges to provide wellbeing and relations to nature and teach gardening principles to beginners as a hobby. Participation in the communal garden is free of charge.
Water retention of one of the larger issues in the Lapinlahti Garden Community, as it is not possible for most of them to visit the garden frequently enough to water the plants sufficiently. The gardeners were already aware of biochar as a potential solution for this challenge, but partly due to its high price it was never considered a viable option. In total 1250L of biochar was delivered to these garden communities, which was activated and applied during ‘talkoots’ (collective works) in the spring.
Inner courtyards are located on the intersection of public and private space, and in Finland are often managed through a housing cooperation. Which offers a potentially interesting legal structure for citizen engagement. Especially related to the need of adapting houses to climate change.
Rinnekodit is a housing association that is conducting a pilot project in which it is creating a community setting providing support to help formerly homeless people to reintegrate into society. This pilot project takes place in a housing block in Eastern Helsinki. Gardening in the inner courtyard is part of the reintegration program. Small adjustments to the inner courtyard have been made to facilitate communal activities and enable community gardening. The coordinators working for Rinnekodit did not have much experience with gardening prior to the project and are learning through trial and error.
Using biochar was part of a larger event to kick-off Rinnekodit’s project to convert the inner courtyard into a therapeutic garden. Adding biochar to 6 pre-existing garden boxes, installing a new garden box with annual flowers, amending soil around already present berry bushes, adding biochar to a planting area next to a sidewalk, and donating and constructing a planter box filled with compost and biochar to a neighboring elderly home.
Rooftops provide are an underutilized space for potential urban green. Because biochar is light in weight and has a large nutrient and water holding potential, it can be an interesting instrument in creating special soils for rooftops.
On top of the roof of Kaapelitehdas, an arts and culture centre in Western Helsinki, a group of 40 raised garden boxes belong to a community of gardeners who also rent studios in the building.
250L of dry biochar was delivered to the rooftop garden of the Kaapelitehdas. In advance a leaflet with information on how to activate and apply biochar was distributed to one of the coordinators of the rooftop garden, who forwarded it to the gardening community. The gardeners were free to decide how they wished to apply the biochar and for what purposes. In addition, one of the garden boxes was reserved to do a comparative test with a selection of native plants that attract pollinators. 10L of activated biochar (with nettle tea) was mixed in one half of the soil, while the other half did not receive any biochar.
To promote the project in an engaging way amongst citizens and other stakeholders, a small-scale exhibition module was developed. These modules contain conceptual representations of some of the biochar experiments conducted in Helsinki, visualizations of the concept of the project, the potential of biochar in urban environments, the utility of biochar in soils, and samples of the feedstocks. In addition, the exhibition modules can be complimented with the distribution of biochar in the 3L bags containing woodchip biochar from one of the experimental feedstocks; 3 large posters (90x135cm); and an instruction manual on how to use biochar at home.
All communication materials are designed according to the visual branding guidelines of the City of Helsinki. If you are interested in exhibiting these modules or posters, please contact Miina Heikkinen miina.heikkinen[at]aalto.fi
Events related to the Helsinki Biochar Project
The Biochar Tour was organised on the 6th of september 2023together with one of the garden coordinators at the Lapinlahden Lähde community garden. The goal of the tour was twofold: 1) to inform the participating citizens of the citizen engagement trials on the larger scope of the project, and 2) to bring in members from the steering team to facilitate knowledge exchange between professional experts and citizens.
Biochar. In the City?
On the 16th of March had a public discussion about the role of biochar in the climate work of cities. The project responsibles, Mikko Jalas (Aalto) and Susanna Kankaanpää (Helsinki) presented their current views and answered to questions from the public. The event was a part of NODUS Talks continuum at the Helsinki Design Museum and its recording can be viewed on Aalto Youtube channel.
Join us on the upcoming Sustainability Science Days 2023 in the session "Scaling Up Urban Carbon Sinks with Urban Green Infrastructure". The Sustainability Science Days is an international, multi-day conference organised jointly by Helsinki Institute of Sustainability Science (HELSUS) and Aalto University on 23 - 26th of May 2023.
The session brings together climate, material, soil and social scientists; landscape architects and urban planners; practitioners and businesses; and municipalities and governmental bodies. The aim is to bring forward academic knowledge and practices on the conditions and current ways of scaling up urban carbon sinks and developing carbon smart Urban Green Infrastructure for development of municipal strategies and decision-making, planning, as well as construction and maintenance practices.
The Helsinki Biochar Project builds on previous collaboration projects on biochar
Carbon Lane (CarLa) is an EIT Climate-KIC funded project which takes place during 2019. The project explores practical carbon drawdown solutions for urban green areas
Hiilipuisto project launches scientific monitoring of biochar-based planting soils and develops sustainable practices in the green building sector.
- Susanna Kankaanpää, Helsinki Urban Environment Division, Climate Unit
- Prof. Mikko Jalas, Aalto University
- Tuuli Markkanen, Project Coordinator, Aalto University tuuli.markkanen[at]aalto.fi
- Will van Twuijver, Project Coordinator in citizen engagement and visual communication, Aalto University. (December 2022- November 2023)
- Miina Heikkinen, contact person for exhibitions and other outreach, miina.heikkinen[at]aalto.fi
Funding and support from abroad
Bloomberg Philanthropies announced that seven cities from Europe and the United States will receive support to adopt Stockholm’s 2014 Bloomberg Philanthropies’ Mayors Challenge Winning Biochar Project, which turns plant waste from parks and homes into a charcoal-like substance that residents can then use in their yards and gardens to help combat climate change.
Darmstadt, Helsingborg, Sandnes, Helsinki, Cincinnati, Lincoln, and Minneapolis, will receive funding, along with implementation and technical support from Bloomberg Philanthropies to develop city-wide biochar projects and engage residents in the fight against climate change. Participating cities will also benefit from robust best practice sharing and peer-to-peer networking to share lessons learned in implementing their efforts
Useful sites to read and follow regarding biochar use in urban green structures
Several cities across the globe have started initiatives to promote biochar use to fight climate change.