This study aimed to investigate the climate impacts of carbon sequestration in forests, and the substitution of fossil energy (e.g., coal, oil) and fossil-based materials (e.g., concrete, steel, plastic) with harvested energy biomass and timber (pulpwood, sawlogs) under Finnish boreal conditions. The study employed forest ecosystem model simulations and a life cycle assessment tool to calculate the net CO2 exchange for the forest-based biosystem. The effects of stocking in thinning, nitrogen fertilization, and the use of varying rotation lengths and harvest intensities in final felling (timber, logging residues with and without coarse roots and stumps) on the climate impacts and economic profitability of biomass production were studied. Current Finnish forest management recommendations for thinning, aimed at timber production, were used as a baseline. In addition, the sensitivity of climate impacts to displacement factors and timber use efficiency was studied. This work was conducted at the stand level, with a mature stand as a starting point (Paper I), at the landscape level, under alternative initial forest age structures (Paper II), and at the regional level, using national forest inventory data in southern Finland.
This study revealed that the best option for increasing the climate impacts of biomass production and utilization was through maintaining up to 20% higher stocking, nitrogen fertilization, and using 80–100-year rotations, since they increased carbon sequestration and timber and energy biomass yields. However, there was a tradeoff between the greatest climate impact and the economic profitability of biomass production.Sawn wood products were the best option for long-term substitution and increasing carbon stocks of wood products. It was also found that the effects of substitution and timber use efficiency on climate impacts were higher than those of the thinning regimes. Consequently, the greatest climate impacts were found when intensified biomass harvesting was performed, and the prominent regions for increasing climate impacts over the next 40-year period were the southern and eastern sub-regions of Finland. Furthermore, the climate impacts were found to be sensitive to the initial conditions set for the analyses, which affected the timing of the climate impacts and the preference of forest management in climate change mitigation. This indicates that management measures, together with the initial conditions of the forests, should be considered when evaluating efficient options for increasing climate impacts by forests and substitution.