Realizing the energy potential of forest biomass in Sweden - How much is environmentally sustainable?

- Increased use of wood for bioenergy will have both positive and negative impacts on environmental objectives.
- The harvest can be three times higher than current harvesting level, and still be sustainable.
- Mitigations and compensations measures are required to be able to increase harvesting in a sustainable way.

Harvesting of wood for bioenergy purpose will probably increase in importance in the future, in order to replace fossil fuel. However, the environmental impact of increased harvesting might be considerable, e.g. on soil and water chemistry, biodiversity and long-term productivity, and in this study we investigate thresholds for sustainable harvesting volumes. The study is based on scientific reviews of the impact of harvesting of logging residues (slash and stumps) on forest production, biodiversity, acidification, eutrophication and toxic substances. We define sustainability by using environmental objectives decided by the Swedish parliament (which are based on the Aichi targets), and relate the harvesting impact to these objectives within different harvesting scenarios, by using expert judgment. We demonstrate that an increase in harvesting of logging residues by 2.5 times might be sustainable. However, we also identify a number of risks and the sustainability depends on a number of requirements that should be fulfilled, such as ash-recycling. It was found that factors related to biodiversity conservation (defined in the goals 'Sustainable Forests' and 'A Rich Diversity of Plant and Animal Life') were limiting factors both for slash- and stump harvesting, and that risk of acidification (defined in the goal 'Natural Acidification Only') also limit slash harvesting. We also include harvesting of brushwood and energy wood from conservation cutting in the discussion, since these assortments might be important in the future.