Life cycle assessment – forestry and climate
Forestry has a key role in a future bioeconomy, by providing wood fibres for biomaterials and bioenergy. The climate effects of forestry and wood-based products is however debated. One explanation for contradictory viewpoints is represented by different methodological settings in climate impact calculations, for example regarding system boundaries and chosen time perspective.
This research project will assess the climate effects of forestry and wood products applying a broad system perspective including value chain emissions, biogenic carbon stocks in forest land and temporarily stored in wood products, and the potential climate benefit from replacing greenhouse gas-intensive materials and energy, which is called substitution effect.
The climate effect will be assessed from a life cycle perspective using a time-dependent method, meaning that the timing of greenhouse gas fluxes are considered and the climate impact is expressed in temperature change over time (in addition to CO2-equivalents). Forest carbon dynamics and biogenic carbon stored temporarily in wood products will be modelled over time. Moreover, new substitution factors will be developed for different types of wood products.
The aim of this report was to assess the climate impact of a forestry company (Stora Enso) using a full system perspective, meaning that value chain emissions for producing wood products and bioenergy, biogenic carbon fluxes from forest land and carbon temporarily stored in wood products were considered. Additionally, the potential climate benefit from substitution was considered, which means avoided emissions when wood is used instead of greenhouse gas-intensive materials and energy.
Life cycle assessment was basis for the analysis and the results show that the estimated climate effect at corporate level was a net removal of -11.5 million Mg CO2-eq per year (meaning a climate benefit). Uptake of biogenic carbon counteracted around 40% of the value chain emissions, while the largest climate benefit (removal of 17.9 million Mg CO2-eq) was due to substitution of more greenhouse gas-intensive products. The study adds to previous research by developing several new substitution factors for paper and pulp products and by performing dynamic modelling of forest carbon stock changes and temporarily carbon storage in harvested wood products.
Hammar, T., Hansson, P.A., Seleborg, M. & Stendahl, J. (2020). Climate effects of a forestry company – including biogenic carbon fluxes and substitution effects. Report 114, Dept. of Energy and Technology, Uppsala. Swedish University of Agricultural Sciences (SLU).