Effects of forest management on the carbon dioxide emissions of wood energy in integrated production of timber and energy biomass

Abstract

The aim of this work was to study the sensitivity of carbon dioxide (CO 2 ) emissions from wood energy to different forest management regimes when aiming at an integrated production of timber and energy biomass. For this purpose, the production of timber and energy biomass in Norway spruce [Picea abies (L.) Karst] and Scots pine (Pinus sylvestris L.) stands was simulated using an ecosystem model (SIMA) on sites of varying fertility under different management regimes, including various thinning and fertilization treatments over a fixed simulation period of 80 years. The simulations included timber (sawlogs, pulp), energy biomass (small-sized stem wood) and/or logging residues (top part of stem, branches and needles) from first thinning, and logging residues and stumps from final felling for energy production. In this context, a life cycle analysis/emission calculation tool was used to assess the CO 2 emissions per unit of energy (kg CO 2 MWh À1 ) which was produced based on the use of wood energy. The energy balance (GJ ha À1 ) of the supply chain was also calculated. The evaluation of CO 2 emissions and energy balance of the supply chain considered the whole forest bioenergy production chain, representing all operations needed to grow and harvest biomass and transport it to a power plant for energy production. Fertilization and high precommercial stand density clearly increased stem wood production (i.e. sawlogs, pulp and small-sized stem wood), but also the amount of logging residues, stump wood and roots for energy use. Similarly, the lowest CO 2 emissions per unit of energy were obtained, regardless of tree species and site fertility, when applying extremely or very dense precommercial stand density, as well as fertilization three times during the rotation. For Norway spruce such management also provided a high energy balance (GJ ha À1). On the other hand, the highest energy balance for Scots pine was obtained concurrently with extremely dense precommercial stands without fertilization on the medium-fertility site, while on the low-fertility site fertilization three times during the rotation was needed to attain this balance. Thus, clear differences existed between species and sites. In general, the forest bioenergy supply chain seemed to be effective; i.e. the fossil fuel energy consumption varied between 2.2% and 2.8% of the energy produced based on the forest biomass. To conclude, the primary energy use and CO 2 emissions related to the forest operations, including the production and application of fertilizer, were small in relation to the increased potential of energy biomass.

Climate Change Mitigation Potential in Boreal Forests: Impacts of Management, Harvest Intensity and Use of Forest Biomass to Substitute Fossil Resources

“…The performance of SIMA model has been reported earlier and the simulated growth and the measured mean annual [49]. In addition, the simulations have found a good agreement with the empirical growth and yield model Motti [50] in the simulations of volume growth of managed Norway spruce (Picea abies L. Karst) and Scots pine (Pinus sylvestris L.) stands in 13 different locations from southern to northern Finland on medium fertile sites over an 80-year rotation period [16].…”

“…Current Finnish forest management recommendations aim mainly at timber (sawlogs and pulpwood) production and there may be a need to modify these if both carbon sequestration and production of timber and energy biomass are aimed to be increased to promote emission mitigation (e.g., Matala et al [15]; Routa et al [16]). Carbon sequestration into forests can be increased by using less intensive thinnings and higher stocking over a rotation period, but this may decrease the economic profitability of the production due to a delay in harvesting (e.g., Pyörälä et al [17]).…”

Temporal and Spatial Change in Diameter Growth of Boreal Scots Pine, Norway Spruce, and Birch under Recent-Generation (CMIP5) Global Climate Model Projections for the 21st Century

“…The model comparison by Routa et al [35] also indicated good agreement between simulations using the gap-type forest ecosystem model SIMA and the empirical growth and yield model MOTTI [32] for the mean annual volume growth, with and without N fertilization, of managed Norway spruce and Scots pine stands on medium fertile upland forest sites.…”

Time-Dynamic Effects on the Global Temperature When Harvesting Logging Residues for Bioenergy

“…In all three regions, the study was limited to Norway spruce (Picea abies). The harvest of aboveground energy biomass is generally integrated with the harvest of timber in conventional forestry in Sweden [29], and therefore the release of GHG and energy consumed prior to and during final felling were allocated to the production of timber. The management practices and technologies used were assumed to be constant during the whole lifespan of the forest and no improvements were considered.…”