Johanna Routa

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

The aim of this work was to study the sensitivity of carbon dioxide (CO2) 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 CO2 emissions per unit of energy (kg CO2 MWh−1) which was produced based on the use of wood energy. The energy balance (GJ ha−1) of the supply chain was also calculated. The evaluation of CO2 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 CO2 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−1). 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 CO2 emissions related to the forest operations, including the production and application of fertilizer, were small in relation to the increased potential of energy biomass.

Precision measurement of forest harvesting residue moisture change and dry matter losses by constant weight monitoring

The moisture content of forest-wood chips is one of the most important quality factors for the rapidly growing bioenergy sector. Rising transportation costs and increased use of forest biomass for energy are forcing biomass suppliers towards better moisture-content management in the supply chain. In the literature, numerous studies on natural drying of forest biomass have been conducted based on traditional sampling of piles or weighing. The latest methodology for moisture-change monitoring has been constant weighing of piles in racks built on load cells. In this study, seven piles of logging residues were monitored for between 35 and 85 weeks in Finnish climatic conditions. In addition, two small piles which imitated drying in stand conditions were monitored for 6 weeks. After 8 months of drying, a remarkable dry-matter loss was observed in the logging residue piles.

Effects of Forest Management on Total Biomass Production and CO2 Emissions from use of Energy Biomass of Norway Spruce and Scots Pine

The aim of this study was to analyze the effects of forest management on the total biomass production (t ha-1a-1) and CO2 emissions (kg CO2 MWh-1) from use of energy biomass of Norway spruce and Scots pine grown on a medium fertile site. In this context, the growth of both species was simulated using an ecosystem model (SIMA) under different management regimes, including various thinning and fertilization treatments over rotation lengths from 40 to 120 years in different pre-commercial stand densities. A Life Cycle Analysis/Emission calculation tool was employed to assess the CO2 emissions per unit of energy from the use of biomass in energy production. Furthermore, the overall balance between the CO2 uptake and emission (carbon balance) was studied, and the carbon neutrality (CN) factor was calculated to assess environmental effects of the use of biomass in energy production; i.e., how much CO2 would be emitted per unit of energy when considering direct and indirect emissions from forest ecosystem and energy production. In general, the total annual biomass production for both species was highest when management with fertilization and high pre-commercial stand density (4000–6000 trees ha-1) was used. In the case of Norway spruce, the highest annual biomass production was obtained with a rotation length of 80–100 years, while for Scots pine a rotation length of 40–60 years gave the highest annual production. In general, the CO2 emissions decreased along with an increasing rotation length. The reduction was especially large if the rotation length was increased from 40 years to 60 years. Scots pine produced remarkably smaller net CO2 emissions per year (on average 29%) than Norway spruce over all different densities and rotation lengths. The value of the CN factor was highest if a rotation of 100 years was used for Norway spruce stands and a rotation of 120 years for Scots pine. The CO2 emission per energy unit was substantially less than that from the use of coal, which was used as reference to assess environmental effects of the use of biomass in energy production. The use of higher density of pre-commercial stand than that currently recommended in the Finnish forestry, together with timely thinning and fertilization, could increase the total biomass production, but also simultaneously decrease the net CO2 emissions from the use of energy wood.

Modeling the effects of climate change and management on the dead wood dynamics in boreal forest plantations

Abstract The present research examines the joint effects of climate change and management on the dead wood dynamics of the main tree species of the Finnish boreal forests via a forest ecosystem simulator. Tree processes are analyzed in stands subject to multiple biotic and abiotic environmental factors. A special focus is on the implications for biodiversity conservation thereof. Our results predict that in boreal forests, climate change will speed up tree growth and accumulation ending up in a higher stock of dead wood available as habitat for forest-dwelling species, but the accumulation processes will be much smaller in the working landscape than in set-asides. Increased decomposition rates driven by climate change for silver birch and Norway spruce will likely reduce the time the dead wood stock is available for dead wood-associated species. While for silver birch, the decomposition rate will be further increased in set-aside in relation to stands under ordinary management, for Norway spruce, set-asides can counterbalance the enhanced decomposition rate due to climate change thereby permitting a longer persistence of different decay stages of dead wood.

The timber and energy biomass potential of intensively managed cloned Norway spruce stands

We used ecosystem model simulations to study the timber and energy biomass potential offered by intensively managed cloned Norway spruce stands. More specifically, we analysed how the use of cloned trees compared with non‐cloned trees, together with thinning, nitrogen (N) fertilisation and rotation length (from 60 to 100 years), affects the annual mean production of timber (i.e., saw logs, pulpwood) and energy biomass (i.e., stumps and harvesting residuals in the final felling) and its economic profitability [annual mean of net present value (NPV) with a 2% interest rate]. Furthermore, we employed a life cycle analysis/emission calculation tool to assess the total net CO2 emissions per unit of energy (kg CO2 MW h−1) produced based on energy biomass. We found that both the annual mean production of timber and the NPV increased substantially, regardless of the management regime, if cloned trees with an annual growth increase of up to 30% compared with non‐cloned trees were used in regeneration. In general, the use of a short rotation with N fertilisation clearly increased the annual mean of the NPV. Consequently, the use of cloned trees also clearly increased the annual mean production of energy biomass and decreased the total net CO2 emissions per unit of energy produced based on energy biomass. However, the total annual net CO2 emissions were the lowest if a long rotation was used with N fertilisation. To conclude, the use of cloned trees together with intensive management could potentially be highly beneficial for the cost‐efficient and sustainable production of timber and energy biomass in an integrated way.

Reengineering business processes to improve an integrated industrial roundwood and energywood procurement chain

Procurement systems and supply chains for industrial-scale forest fuel recovery are still immature. Business process improvement techniques can significantly improve system performance. The present study applies business process modeling and reengineering approaches to an integrated industrial roundwood and energywood supply chain in Germany. The existing business process was reengineered. A new business process for integrated industrial roundwood and energywood procurement and two new business processes for future biomass procurement operations were designed using proven best practices. The improvement potential of the new business processes was investigated by determining the organizational and managerial workload of all actors using discrete-event simulation. The results of the discrete-event simulation were then used as a basis for a comprehensive cost calculation. Finally, the cost-saving potential relative to the current practice was determined. The redesign of the current business process provides a cost-saving potential of 20–39% (–2.64 to –5.25 USD/m3). The first biomass procurement process involves a saving potential of 12–53% (–1.60 to –7.20 USD/m3), while the second might even increase the costs by 13% if the probability of failures is high. With decreasing probability of failures, the costs can decrease by up to 32% (+1.76 to –4.27 USD/m3). The study demonstrates that simple and low-cost measures can improve business processes in forest supply chains and achieve considerable cost savings.

Integrated Production of Timber and Energy Biomass in Forestry

Current management aimed purely at producing timber is not necessarily appropriate in managing forests to combine the production of timber and energy biomass and to maintain or even to increase carbon storage in forest ecosystems. Key questions are; how to integrate the management efforts to enhance the production potentials, how to sustain the production (e.g. carbon and nutrient balances), and what their overall economic implications are for forestry. Proper choice of tree species and improved clones in planting, spacing (planting density, thinning regimes), rotation length, and fertilization are important in enhancing the combined production of timber and biomass, in increasing carbon stocks in forest ecosystems, and in the mitigation of climate change.

Weather based moisture content modelling of harvesting residues in the stand

Harvesting residues collected from the final cuttings of boreal forests are an important source of solid biofuel for energy production in Finland and Sweden. In the Finnish supply chain, the measurement of residues is performed by scales integrated in forwarders. The mass of residues is converted to volume by conversion factors. In this study, weather based models for defining the moisture content of residues were developed and validated. Models were also compared with the currently used fixed tables of conversion factors. The change of the moisture content of residues is complex, and an exact estimation was challenging. However, the model predicting moisture change for three hour periods was found to be the most accurate. The main improvement compared to fixed tables was the lack of a systematic error. It can be assumed that weather based models will give more reliable estimates for the moisture in varying climate conditions and the further development of models should be focused on obtaining more appropriate data from varying drying conditions in different geographical and microclimatological locations.

Dry matter losses and their economic significance in forest energy procurement

ABSTRACT The value chain of forest biomass for energy always includes storing of the biomass. Biomass in natural conditions is always exposed to biological processes, some of them harmful. Dry matter losses caused by biological processes, such as composting and decaying, were studied by the weight monitoring method. After defining dry matter losses as 0.07–1.52% per month for small size delimbed roundwood under study, the total amount and economic scale of losses were calculated to gain an understanding about the phenomenon from the value chain management point of view. Losses during energy wood storing may be significant even with 3–6 months of storing. With 1-year storing time, economic losses varied between 91,000 and 373,000 euros, if the amount stored is 100,000 m3. The economic losses were 4–17% of the energy wood procurement costs, depending on the storage time, raw material and dry matter loss rate. Energy content of the storage can increase during the 12-month storage period if the dry matter losses are low, which requires careful storage management of energy wood.

Hybrid solutions as a measure to increase energy efficiency – study of a prototype of a hybrid technology chipper

ABSTRACT The objectives of this study were to examine the new hybrid technology chipper, Kesla C 860 H in comparison to two conventionally diesel-powered chippers, when chipping conifer pulpwood and logging residues. Productivity, fuel consumption and quality of the chips were measured and analyzed. During the time studies, both the chipper and hybrid system were working well. Chip quality was good and met the demands of small-scale residential boiler users. The average chipping productivity of the hybrid chipper unit was 13.1 oven dry metric tonnes (odt) per effective hour (E0h) when chipping logging residues and 11.3 odt E0h−1 when chipping pulpwood. This was lower than for the conventional chippers which produced 20.1 odt E0h−1 when chipping logging residues and 31.2 odt E0h−1 and 14.0 odt E0h−1 when chipping pulpwood. Fuel consumption of the hybrid chipper was 2.9 litres per odt for logging residues and 3.1 litres per odt when chipping conifer pulpwood, which was slightly lower than for the conventional chippers. Compared to conventional chippers, the hybrid chipper was more energy efficient and consequently produced the least amount of emissions per odt of chips. The productivity results of this study must be considered with care as the chipper and especially the hybrid system are under continuous development, and follow-up studies are needed to determine long-term productivity, fuel consumption and operating costs.