Finnish forest carbon sinks and carbon storages have been a hot topic in the public debate in recent years. What is a carbon sink and how does it relate to products made from wood?
Carbon sink means a carbon storage that binds more carbon dioxide than is freed into the atmosphere. The most important carbon sinks in Finland are forests and the tree stands they contain, as well as soil. Roughly half of the carbon that is sequestered in forests is stored in the soil. Carbon sinks are very important in terms of mitigating the impacts of climate change.
A growing forest is an effective carbon sink, whereas a decomposing tree already begins to release carbon into the atmosphere. Active forest management, forest regeneration and increased forest growth thus guarantee the existence of carbon sinks also for future generations.
What happens to a tree and the carbon stored in it when the tree is cut down? Trees don’t stop storing carbon instantly when they are cut down; rather, the stored carbon is released into the atmosphere only once the tree is combusted, for example, as bioenergy in heat production. Practically the same amount of carbon dioxide is released when the tree is combusted as was stored in it while it grew.
In Finland, only less than 10 per cent of trees that are felled are combusted, which means that more than 90 per cent of felled trees continue to serve as carbon storages even after they are cut down.
Forty-nine per cent of the mass of wood products is carbon, and they bind an average of one tonne of carbon dioxide for every cubic metre. Carbon is stored in wood products for their entire life cycle, which includes their use, re-use and recycling. Carbon is only released when the wood product is used for energy production or it decomposes. The longer the wood product is used, the longer it serves as a carbon storage. For example, well-maintained wooden structures can last as long as 75 years, which is a significant amount of time to store carbon dioxide. A good example of how wood acts as a carbon storage is a wooden house, which stores the same amount of carbon as the amount emitted by a car used for ten years by a family of four.
Carbon stored in wood products helps reduce the amount of carbon dioxide in the atmosphere, just like growing forests. The importance of wood products in binding carbon dioxide becomes increasingly important if they can be used to replace other materials, such as steel, plastic and concrete, which consume more fossil fuels.
Their ability to bind carbon is not the only reason to make use of trees. Trees are renewable and easily recyclable; their various parts can be efficiently used either in wood products or as bioenergy. Koskisen also makes use of every last wood chip from the wood raw material that comes to the mill. Chipboard is an excellent example of getting the most out of a tree and its by-products.
At Koskisen’s chipboard mill, the only one in Finland, chipboard is made mostly from virgin wood – from the sawdust that is produced during the sawmilling process. Panel products made from chipboard continue to act as carbon storages in homes – in floor and wall structures, in furniture and in kitchen cabinetry. The carbon footprint of chipboard encourages its use.
“Chipboard basically has a negative carbon footprint, if you take into account the product’s carbon sink effect. It is otherwise common that the sawdust produced by the sawmill is combusted and therefore does not bind carbon,” explains Jukka Rautiainen, Production Manager at Koskisen’s Chipboard mill.
Sources: Finnish Forest Industries Federation, WoodProducts.fi