READ MORE ABOUT CARBON STORAGES
A GROWING TREE ABSORBS CARBON When a tree grows by a cubic metre or so, it absorbs around 900 kilos of carbon dioxide. 900 kilos
WOODEN HOUSES STORE CARBON The amount of carbon in one cubic metre of sawn timber is around 200 kilos. Around 4,000 kilos of carbon are seques- tered in a detached wooden house of 100 square metres. 4,000 kilos
Wood products provide significant carbon storage Growing forests remove carbon dioxide from the atmosphere, and sawn timber stores carbon for decades.
MARKKU RIMPILÄINEN, photo LINA JELANSKI/DUOTONE
Carbon sequestration in trees begins with photosynthe- sis. Growing trees use sunlight to produce glucose from water and atmospheric carbon dioxide, and then convert the glucose mainly into cellulose. Trees store the carbon contained in carbon dioxide in their trunks, branches, leaves and roots. When a tree grows by a cubic metre, it absorbs around 900 kilos of carbon dioxide. Carbon is absorbed most ef- fectively by trees in their prime growing phase – in Finland when trees are 20 to 60 years old. As a tree gets older, growth slows and it cannot absorb carbon like before. A forest is as a whole a huge store of carbon. The car- bon storage of an old forest is many times that of a young forest. The largest amount of carbon is stored in in the organic matter contained in the forest soil. FOREST MANAGEMENT ACCELERATES FOREST GROWTH In 2019, forest growth in Finland was 107 million cubic metres. A total of 71 million cubic metres of wood was harvested – markedly less than the annual growth. Forest growth in Finland has accelerated over the last 50 years. In the 1980s, the average growth per hectare was 2.4 cubic metres. The growth rate has since doubled and is now 4.8 cubic metres per hectare. The fastest for- est growth rate has been recorded for the Päijät-Häme region in southern Finland, at around eight cubic metres per hectare. The acceleration is partly due to global warming, but mostly due to good forest management. When brush- wood is cleared and young forests are thinned, the re- maining trees grow more quickly. For example, in initial thinning 60 cubic metres of wood are felled per hectare. The volume is around 100 cubic metres in the second thinning and around 250
cubic metres per hectare in the final felling. In the con- tinuous cover model, around 75 cubic metres of wood per hectare are harvested regularly. THE CARBON REMAINS IN SAWN TIMBER A log’s most valuable part is the section suitable for saw- mills. In Finland, it is around 40 per cent of the annual felling volume. In order to have a cubic meter of sawn timber, you must first have about two cubic meters of raw wood material. The sturdy parts of a trunk are used for sawn timber. The chips generated during sawing are used to produce pulp, and sawdust and bark are used to produce bioenergy. The carbon sequestered in a tree remains in the sawn timber. The amount of carbon in one cubic metre of sawn timber is around 200 kilos. Each house built of wood is a small store of carbon. A detached house of 100 square metres can sequester around 4,000 kilos of carbon. WOOD REPLACES FOSSIL RAW MATERIALS Wood products have the unique ability to store carbon. The longer buildings are in use, the longer the carbon stays out of the atmosphere. The use of wood reduces carbon emissions from fossil fuels and fossil-based products. This phenomenon is known as the substitution effect. Sawn timber has a high substitution effect. Metsä Group aims to increase the amount of carbon sequestered in its products by 30 per cent by 2030. This goal can be achieved by producing wood products with long lifespans, such as sawn timber and engineered wood products. The sawmill built in Rauma will sig- nificantly increase the manufacture of wood products. •
Riikka Joukio Metsä Group's SVP of Climate and Circular Economy, was the expert consulted for this text. Sources: Natural Resources Institute Finland (Luke), The Finnish Timber Council, Metsä Group.
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