BIOENERGY FROM BOREAL FORESTS Swedish approach to sustainable wood use

 Bioenergy, most of it from forests, accounts for three-eighths of all the energy used in Sweden. Swedish forests have doubled in volume over the last century. They have therefore doubled their capacity to absorb carbon and to provide wood for energy and a variety of other uses. As the land area covered by forests has changed very little, this is due to more productive use of the land. The strategy that has brought this about may be useful to consider for other boreal forests.

Central to the strategy is active forest management, with constantly improving methods and practices, which leaves a portion of each year’s forest growth in place when wood is harvested, replants the harvested area with new trees, and uses wood harvested in an efficient, sustainable manner. About three‑quarters of the annual forest growth is harvested, while the remaining quarter is left in place, continuing to provide carbon uptake and other ecosystem services. Wood is typically harvested around every 60 to 100 years, allowing for new trees to be planted. New trees grow faster than old trees, collectively adding more mass to the forest than if trees were left to grow indefinitely. Actively managed and monitored forests are also more resistant to forest fires and infestations, reducing the risk of massive carbon dioxide release from such catastrophes.

Wood energy potential could be significantly enhanced by collecting a larger share of logging residues. Just slightly more than half of the harvested wood is roundwood from tree trunks, which is used for lumber, other wood products, pulp and paper. Turning roundwood into such products yields processing residues for energy use. But the rest of the fellings are tree stumps and “slash” from tops, branches and twigs. Such logging residues are mostly left in the forest to rot, releasing carbon dioxide. While some are needed to support biodiversity by providing habitats for flora and fauna, more could be collected and combusted or otherwise used to displace carbonintensive fossil fuels.

Carbon uptake potential from forests could be enhanced through the focused application of fertiliser. Such directed use of fertiliser has been shown to double the rate of tree growth. Carbon uptake could also be enhanced by developing wood-based alternatives to fossil fuels, such as gasification processes for converting wood to renewable jet fuel. Further carbon uptake is possible in buildings, where wood can displace carbon-intensive construction materials like steel and concrete while continuing to store the carbon that was taken in by the trees from which it was produced. According to recent studies, about 2 tonnes of carbon dioxide emissions are avoided for every tonne of wood used in buildings. Efforts to increase the use of lumber in buildings, as well as the use of composite materials made from low-quality wood residues, could significantly improve global carbon balances.

Active forest management, greater collection of forest residues, focused use of fertiliser, and increased use of wood in buildings can be worthwhile strategies for boosting carbon uptake and energy output from any boreal forest. The potential is substantial not just in Sweden, but throughout Europe, as well as in Canada and Russia. Globally, boreal forests represent a very large carbon sink and energy source, and their role could be significantly enhanced.