The EU should produce 20% of their energy from renewable sources, including bioenergy, by 2020. Each member state has their own target, for example, Finland should produce 38% and Sweden 49% of their energy from renewable sources by 2020. In this context, the development of forest energy utilization and more effective and economic supply systems plays an important role in both countries. The Nordic countries are the world leaders in the utilization of forest biomass for energy production. This paper provides a short overview of the driving forces behind the current technical solutions of forest energy procurement systems in Finland and Sweden and some perspectives on possible future developments. At the moment, the by-products from forest industries (e.g., sawdust, black liquor) have a high degree of utilization in both countries. Additional raw materials for energy production include logging residues, stump and root wood, small diameter wood, and other wood not in demand by the traditional forest industries. Forest energy supply chains may be characterized based on the location of comminution into roadside comminution, terminal comminution, or comminution at a plant. The productivity of the generally highly sophisticated and costly procurement machinery is, to a large extent, dependent on the operator's skills and thus new technological solutions should be developed to improve their usability and consequently efficiency. C 2012 John Wiley & Sons, Ltd.

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.

The aim of this study was to analyze the effects of intensive management and forest landscape structure (in terms of age class distribution) on timber and energy wood production (m 3 ha −1 ), net present value (NPV, € ha −1 ) with implications on net CO 2 emissions (kg CO 2 MWh −1 per energy unit) from energy wood use of Norway spruce grown on medium to fertile sites. This study employed simulations using a forest ecosystem model and the Emission Calculation Tool, considering in its analyses: timber (saw logs, pulp) and energy wood (small-sized stem wood and/or logging residuals for top part of stem, branches, and needles) from the first thinning and harvesting residuals and stumps from the final felling. At the stand level, both fertilization and high pre-commercial stand density clearly increased timber production and the amount of energy wood. Short rotation length (40 and 60 years) outputted, on average, the highest annual stem wood production (most fertile and medium fertile sites), the 60 year rotation also outputted the highest average annual net present value (NPV with interest rates of 1-4%). On the other hand, even longer rotation lengths, up to 80 and 100 years, were needed to output the lowest net CO 2 emissions per year in energy wood use. At the landscape level, the largest productivity (both for timber and energy wood) was obtained using rotation lengths of 60 and 80 years with an initial forest landscape structure dominated by older mature stands (a right-skewed age-class distribution). If the rotation length was 120 years, the initial forest landscape dominated by young stands (a left-skewed ageclass distribution) provided the highest productivity. However, the NPV with interest rate of 2% was, on average, the highest with a right-skewed distribution regardless of the rotation length. If the rotation length was 120 years, normal age class distribution provided, on average, the highest NPV. On the other hand, the lowest emissions (kg CO 2 MWh −1 a −1 ) were obtained with the left-skewed age-class distribution using the rotation lengths of 60 and 80 years, and with the normal age-class distribution using the rotation length of 120 years. Altogether, the management regimes integrating both timber and energy wood production and using fertilization provided, on average, the lowest emissions over all management alternatives considered.

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Bark is currently used mainly to produce energy, but the extraction of valuable compounds before combustion offers an interesting cascading use for debarking biomass. Buffer storage is an inevitable part of bark biomass logistics, but substantial dry matter and extractive losses can degrade the properties and reduce the economic value of the raw material during storage. In this study, moisture and ash content, calorific value, and extractives content and composition of Scots pine (Pinus sylvestris) sawmill bark were determined over 2 months of buffer storage, and the change in energy content during storage was calculated. The results showed that the energy content (MWh m−3) of the bark increased 3% during storage, while at the same time the moisture content decreased 16%. The content of acetone-soluble extractives decreased markedly, with only 56% of the original amount remaining after 8 weeks of storage. In particular, hydrophilic, phenolic extractive compounds were rapidly lost after debarking and piling of the bark. About 60% of condensed tannins (CT) and about 26% of the quantified lipophilic compounds were lost after 2 weeks of storage. The fastest rate of decrease and the most significant changes in extractives content and composition occurred within the first 2 weeks of storage. Utilization of these valuable compounds necessitates fast supply of material for further processing after debarking. The comprehensive utilization of bark requires efficiency at all levels of the supply chain to ensure that tree delivery times are kept short and loss of bark is avoided during harvest and transport.