Net climate impacts and economic profitability of forest biomass production and utilization in fossil fuel and fossil-based material substitution under alternative forest management

Abstract

We studied net climate impacts and economic profitability of the production and utilization of biomass from a Norway spruce (Picea abies L. Karst) stand under alternative forest management in Finnish boreal conditions over 60–100-year rotations. The work employed ecosystem model simulations and a life cycle assessment tool as integrated. The net climate impact of biomass referred to the difference in annual net CO2 exchange between the biosystem and fossil system. Sawn wood, pulp, energy biomass and processing waste substituted for concrete/steel, plastic and coal/oil. In the biosystem, ‘business as usual’ (baseline) and alternative management (maintaining 10–30% higher or lower stocking than the baseline, and/or nitrogen fertilization, and harvesting intensity) were used. The fossil system considered baseline and unthinning as reference management and also net ecosystem CO2 exchange as excluded. We found that using timber and energy biomass generated 32–40% higher net climate impacts compared to using only timber. Generally, harvesting of energy biomass increased the economic profitability but the net climate impacts of biomass were highest over 80–100-year rotations. Maintaining higher stocking in thinning and fertilization generally enhanced net climate impacts, but maintaining up to 20% higher stocking and both energy biomass and timber production increased both net climate impacts and economic profitability. The baseline as a reference produced higher climate benefits compared to unthinning regime. The increased production and use of sawn wood with energy biomass appeared the best option for long-term mitigation, since they enhanced both net climate impacts compared to the fossil system and economic returns.