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Carbon play Alku workshop

How do reeds and pine cones support carbon sequestration? Do you know how peat is used in green areas?

At the Carbon-smart Urban Green Festival last August, CO-CARBON and landscape architecture office Nomaji organised a workshop for children at Central Library Oodi. In the workshop, participants visioned future landscapes and wondered how the play can start: with a bit of imagination, a pile of sand, twigs and pine cones. The idea was to illustrate how carbon-based materials are all around us and how they can be brought into play, while supporting the development of children’s relationship with nature.

Alku is a method developed by Nomaji for designing child-friendly environments. The Alku method provides tools for assessing and considering child-friendliness in different environments. It emphasises the importance of contact with nature and the well-being that comes from nature and helps to create more playful nature in the city. However, the environments created through this method provide well-being and comfort for citizens of all ages.

The workshop was led by CO-CARBON researchers Mari Ariluoma and Caroline Moinel, and designers from Nomaji. Children enthusiastically explored and experimented with different materials and the workshop created a multifaceted sand play landscape from simple elements. Especially families from outside Finland were curious to learn about the materials found in Finnish nature and to identify them not only by sight but also by smell and touch.

Materials used in the workshop

At the workshop, children got to know different natural materials by touching, exploring and looking at them. The following materials were explored and played with:


Reeds grow in abundance along the shores of seas and lakes. Reed can be used in many ways: in green roofs, as a cover, as a growing medium and as a soil improver. Reed can also reduce the need for plastic in green roofs and plantation covers. Its use reduces methane emissions from reeds (source: Myllyviita et al. 2015) and its beneficial use stores carbon.






There are many different kind of cones? Pine cones are woody and rigid, while spruce cones are thinner and more flexible. A tree can produce a large number of cones in a year. In forests, cones decay slowly and fertilise the trees above them, making them part of the carbon cycle.






Pine leaves are made up of a series of needles. The length of the needles varies between species. Did you know that pine trees, for example, drop thousands of needles every year? The needles also contain carbon and contribute to the tree’s carbon cycle. Pine needles are said to be the slowest natural material to decompose. Added in small amounts, needles can be good for compost.





Bark is an outer layer of trees, shrubs and woody vines. It protects the wood from external factors such as drying or burning. The thickness of the bark varies considerably between species. In some species, it can represent up to 20% of the total volume or biomass of the tree (Neumann & Lawes 2020). However, estimating the amount of carbon in the bark remains difficult. Cracks in the bark provide excellent habitat for many species, including insects and spiders (Trees for Life, 2023). Bark can be used, for example, as part of a growing medium or as a soil conditioner.



Natural stones and crushed stone

Stones can be used for an almost infinite number of purposes, for example in construction. Depending on the type of rock and the history of the land, stones come in different shapes, colours and sizes. In construction, natural stones can be reused, making them a sustainable material. Natural stones can be used for paving or kerbstones, for example. Crushed stone is crushed rock or gravel material that is sifted to remove fine particles. When you look around your city, where do you see stones?





There are many different types of rock in the Finnish bedrock. Shale is a very old, sedimentary or layered seabed. Shales break up into slabs of rock on their own due to the composition and formation of the rock. This is why they are easily made into fine paving stones, for example.





Brick rubble

Brick rubble is made of brick. It is a way of recycling and reusing brick material demolished from buildings, giving it a new use, and thus avoiding waste. Bricks are crushed into smaller pieces to form rock material. Possible uses include lightening the substrate, for example as a mound filler, (alternative to light gravel) and surface material as alternative to gravel/rock ash. The use of recycled material reduces the need for a purpose-built product (e.g. lightweight gravel) and the resulting climate burden.





Peat forms in peatlands when decaying plant material accumulates over thousands of years, gradually forming a thick layer. Therefore, peatlands and their peat form a very large carbon pool in the ground. Peat is used for energy production, garden mould, drying agent, animal feed, compost stabilizing medium, soil amendment, fertiliser and oil spill control ( When peat is used, it begins to decompose or is burned, releasing carbon into the air. Peat is a fine material, but its use should be carefully considered to avoid destroying this carbon storage.





A lichen is a symbiotic group of organisms consisting of a fungus and microscopic green algae or cyanobacteria. Lichens grow slowly and thrive in dry places, for example on rocks. Did you know that lichens are also edible?






Mosses are simple and small (usually 1-10 cm) sporiferous plants with very small leaves or no leaves at all. Moss is commonly found in moist places in the shade. Mosses play an important role in soil functioning and carbon cycling.






Dry clay

The clay found in Finnish soils is generally red clay. It is greyish when raw and turns orange or reddish-brown when burnt. Natural clay is used in ceramics, but also as a construction material, a raw material for brick and clay plasters and clay paints. Clay is also suitable as a growing medium because it helps to retain nutrients and moisture.





Sheep’s wool

Sheep’s wool is a natural fibre produced by different breeds of sheep. There are three indigenous breeds in Finland: the Finnish sheep, the Kainuu sheep and the Åland sheep. Also, llamas and goats produce wool. Wool is usually collected from sheep 1-2 times a year. The properties of the fibres influence their use and spinning properties. Wool can be used for felting, but also as insulation, garden coverings or as a material for cushions and blankets (, 2021). Sheep and wool are represented in the carbon cycle as biogenic carbon. 50% of the weight of pure wool is pure biogenic carbon (International Wood Textile Organisation, 2023).




What is this substance that looks like coal? It’s called ‘biochar’. It is made from combustible organic material such as wood. It is burnt at a very high temperature so that no water remains. That’s why it contains a lot of carbon! It is used as a soil amendment for carbon sequestration and soil health.





Cocoa bean shells

Cocoa bean shells are a by-product of cocoa bean production. Although cocoa is not grown in Finland, this material can be seen under bushes in the cities. This so-called mulch is also made from bark and reeds, for example. It is used under flowers, shrubs and perennials and it acts as a fertiliser and helps prevent the spread of weeds.





Sources :

International Wood Textile Organisation (2023). Carbon cycle. (Accessed 7 December, 2023)

Myllyviita, T., Mattila, T., & Leskinen, P. (2015). Järviruo’on niittäminen ja hyötykäyttö. Elinkaariarviointi ympäristövaikutuksista. Suomen Ympäristökeskuksen raportteja 27.

Neumann, M. & Lawes, M.J. (2020). Quantifying carbon in tree bark: The importance of bark morphology and tree size. Methods in Ecology and Evolution 12(4) : 565-766. (2021). Villa. (Accessed 7 December 2023)

Trees for Life (2023). Tree bark. (Accessed 7 December, 2023) Turve sopii moneen käyttöön. (Accessed 7 December, 2023)


Text: Mari Ariluoma & Caroline Moinel, Nomaji

Photos: Caroline Moinel


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