Costs of additional carbon removal and substitution through nitrogen fertilization and extended rotation in Scots pine and Norway spruce stands in Finland

Abstract We investigated, using growth model simulations, how nitrogen (N) fertilization and extending the rotation period affect the quantity and costs of additional CO2 removal in Scots pine and Norway spruce stands on medium-fertile sites in Finland. We compared 14 alternative management regimes, using the management recommended for Finnish forestry as a baseline. The effects of forest management on carbon (C) were examined in terms of net ecosystem CO2 exchange, timber, and the amount of harvested wood products and their substitution (avoided fossil C emissions) effects. Economic consideration was in terms of land expectation value, and the cost of additional CO2 removal was determined against the baseline. The sensitivity of costs to lower interest rate, and lower or higher substitution assumptions were assessed. N fertilization increased the mean annual net ecosystem CO2 exchange for both tree species, but extending the rotation period decreased it. Combination of the methods did not increase C sequestration as much as fertilization alone. Both management regimes reduced the financial return compared to the baseline, except fertilization once in Norway spruce. The costs of additional C removal were 0.1–19.6€/tCO2 with 3% interest rate and higher with lower interest rate. Reducing substitution assumptions (displacement factors for products) increased the calculated costs by 45%, while increased assumptions decreased them. In conclusion, fertilization and extending the rotation period could enhance C storage. However, the associated costs due to additionality were higher for longer rotations and for Scots pine. The system was also sensitive to the assumed substitution effects that have high uncertainty.