Underutilized trees can contribute to a sustainable energy transition

Drone view of mixed forest in autumn colours. Photo.


Stina Johannesson

The energy supply and consumption has been a hot discussion topic among policy-makers, the industry and people in general during the last year. In a Trees For Me research project PhD student Swastika Chakravorty will examine energy value chains based on fast-growing broadleaf trees in the transition towards a sustainable energy system.

One aspect that will be investigated in the research project is how trees currently not desired for industrial uses can be more utilized in the energy value chain.

“Usually, harvesting and collecting small-diameter trees, which could be a potential bioenergy resource, are expensive and the market value of the product is low. On the other hand, too dense forest stands have a negative impact on both tree diameter growth and biodiversity”, says Swastika Chakravorty, PhD student of energy engineering at Luleå University of Technology.

She says that some see early tending and thinning as favorable measures for reindeer husbandry since this opens up the forests, which can facilitate reindeer movement and increase the reindeers’ food supply of ground lichens. One of the questions to be investigated in the research project is whether these additional ecosystem and community service benefits can cover an early cost-intensive harvest of small-diameter trees.

Directives and policies affect use

Elisabeth Wetterlund, professor of energy engineering at Luleå University of Technology and supervisor of Swastika Chakravorty, envisions that smart integrated management systems which make better use of materials from different production types such as agricultural fields, marginal lands, roadsides and early thinnings on forest land, could make small, currently uneconomical, biomass streams more important and profitable. But whether this will be the future reality is affected by the policy and market development.

“Right now, the largest threat to commercialization of any biorefinery processes utilizing woody biomass originating from the forest is the policy development on EU level”, says Elisabeth Wetterlund.

The EU Parliament has the ambition to raise the union’s use of renewable energy to 45 per cent by 2030. However, what should be seen as renewable energy is a source of much debate. In September 2022 the parliament voted that the use of primary woody biomass from the forest, including branches and tree tops, must be gradually phased out in order for the fuel to be considered as renewable. Extracting less biomass from the forest is argued to increase the forest’s role as a carbon sink and its importance for biodiversity.

“The assortments we thought to focus on in this research project, such as thin wood from thinning, will also be restricted from use as renewable energy, despite potentially being beneficial from an environmental perspective. The EU proposition risks being counterproductive in both economic and environmental terms, due to decreased incentives to thin dense young forest stands”, says Elisabeth Wetterlund.

Energy and cost efficiency

To assess the energy efficiency of the value chains the researchers will compare the potential forestry operation alternatives and biomass transportation to the production plant with existing logistics.

“If we can find out the bottlenecks of the bioenergy feedstock production and harvest costs, that would help both forest owners to decide on including bioenergy biomass as a target product and the energy plants to procure feedstock from suitable locations at a suitable cost”, says Swastika Chakravorty.

Page manager: stina.johannesson@slu.se