Category: Research article
article id 10379, category Research article
Productivity of harvesting and clearing of brushwood alongside forest roads. Silva Fennica vol. 54 no. 5 article id 10379. https://doi.org/10.14214/sf.10379
Highlights: The results can be used as a basis to determine in what kinds of cases brushwood biomass should be recovered and where it should be left to decay; The average volume of harvested brushwood and forwarding distance are the key elements to harvesting productivity with a harwarder; Stump diameter has a strong impact on clearing productivity of brushwood.
Expertise in the cost-efficient utilization and treatment of brushwood on forest roadside sites is limited. In the present study, the productivity of brushwood clearing and harvesting on forest roadside sites was defined by creating time-consumption models or parameters for the aforementioned working methods. Compiled time consumption models and parameters for the brushwood clearing and harvesting can be used as a basis for evaluating alternative management practices and to determine when brushwood biomass should be harvested and when it should be left to decay. The harvesting of brushwood was based on the harwarder system and the clearing of brushwood was done with a spiral cutter, which is a novel accessory for cutting roadside vegetation. Based on the study results, the average volume of harvested brushwood and forwarding distance are the key elements that have an effect on harvesting productivity with harwarders. Correspondingly, stump diameter has a strong impact on the clearing productivity of brushwood. The plot-wise productivity of the spiral cutter in brushwood clearings varied in the range of 0.19–0.61 ha per PMh. An increase in stump diameter slowed down the clearing productivity of the spiral cutter and there was a clear step downward in clearing productivity as the average diameter increased from 30 mm to 40 mm. The machinery under study operated well and there were no interruptions due to machine breakdowns.
article id 9902, category Research article
Regional balance of forest chip supply and demand in Finland in 2030. Silva Fennica vol. 52 no. 2 article id 9902. https://doi.org/10.14214/sf.9902
Highlights: The impact of increasing forest chip demand in 2030 was analyzed in Finland; Demand of small trees may exceed potential at the national level; Surplus potential will remain in logging residues and stumps; Hot spots of demand call for efficient logistical solutions.
According to the National Energy and Climate Strategy of Finland in 2016, the demand for forest chips, that is, wood chips made of forest biomass directly for energy use, could even double by 2030 compared to the present situation. A spatially explicit impact analysis of regional supply and demand balances for forest chips was carried out. The balances were calculated as the difference between technical harvesting potentials and demand. First, the technical potentials were estimated based on the national forest inventory data. Secondly, three demand scenarios were defined for 2030 and subsequently deducted from the potentials. The results suggested that there would be increasing competition for feedstock in southern and western Finland, whereas in eastern and northern Finland there would still be surplus potential. Moreover, due to the remarkable deficit of small trees in southern Finland, there might be pressure towards using more pulpwood-sized and/or imported wood in energy production. The results also showed that, in particular, large new plants consuming substantial amounts of forest chips could have a significant effect on the regional availability of forest chips. Moreover, with increasing transport distances, new logistical solutions will be needed.
article id 7830, category Research article
Weather based moisture content modelling of harvesting residues in the stand. Silva Fennica vol. 52 no. 2 article id 7830. https://doi.org/10.14214/sf.7830
Highlights: Weather data used for estimating the moisture content of energy wood; The validation of the weather based models performed based on the field data.
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.
article id 2017, category Research article
From useless thickets to valuable resource? – Financial performance of downy birch management on drained peatlands. Silva Fennica vol. 51 no. 3 article id 2017. https://doi.org/10.14214/sf.2017
Highlights: The most profitable management regimes for pulpwood and energy wood production in dense downy birch stands on drained peatlands include no thinnings, but final cutting at the stand age of 40–45 years as whole-tree harvesting, or as integrated harvesting of pulpwood and delimbed energy wood stems about 10 years later depending on applicable harvesting method; A competitive management regime is early precommercial thinning at 4 m dominant height to a density of 2500 stems per hectare and production of pulpwood with a rotation of 55–65 years. Equal profitability is achieved with or without traditional first thinning, which can thus be included for other reasons, for example to improve regeneration of spruce.
Downy birch (Betula pubescens Ehrh.) stands on drained peatlands are often considered useless because they typically do not yield good-quality sawn timber. However, covering an area of ca. 0.5 million hectares and with total yields of up to 250 m3 ha–1, downy birch stands on peatlands in Finland have a potential for pulpwood and/or energy wood production. We examined the financial performance of alternative management regimes (with or without thinnings, different thinning intensities, several rotation lengths) combined with alternative harvesting methods (pulpwood, energy wood, or integrated, energy wood being delimbed stems or whole trees). We used data from 19 experimental stands, monitored for 20–30 years. For harvesting removals we considered both actual thinning removals and final-cutting removals with alternative timings that were based on the monitoring data. We assessed the profitability as a combination of the net present value of the birch generation and the bare land value of future generations of Norway spruce (Picea abies (L.) Karst.). The most profitable management was growing without thinnings until whole-tree final cutting at the stand age of 40–45 years with an advanced multi-tree harvesting method. In contrast, the standard method in whole-tree final cutting resulted in the lowest profitability, and an integrated method with the energy wood as delimbed stems was the best of the standard methods. Thinnings were unprofitable especially when aiming to produce energy wood, whereas aiming for pulpwood, light precommercial thinning was competitive. Commercial thinning at the traditional “pulpwood stage” had little effect on profitability. The best stand age for final cutting was 40–65 years – earlier for very dense stands and whole-tree energy wood harvesting with advanced method, later for precommercially thinned stands and pulpwood harvesting.
article id 1521, category Research article
First-thinning harvesting alternatives for industrial or energy purposes based on regional Scots pine stand simulations in Finland. Silva Fennica vol. 50 no. 2 article id 1521. https://doi.org/10.14214/sf.1521
Highlights: Small-diameter delimbed wood from Scots pine stands delivered directly for energy use was the most cost-efficient option in terms of the total supply-chain cost in comparison with corresponding industrial use or a whole-tree supply chain for energy use; Forest-management and harvesting decisions influenced the removal of forest biomass and stumpage price as well as the total supply-chain costs for forest biomass; The greatest cost-reduction potential (10.0%, 4.00 € m–3) was achieved for the delimbed energy wood’s supply chain in the regional case of South Savo in eastern Finland.
Combining research into forest management stand conditions and wood supply chain processes has been missing from earlier forestry studies. There is a clear need to develop more cost-efficient small-diameter wood production, harvesting and transportation methods from first thinning, which could be used for either industrial or energy wood purposes. This study considers the total cost for small-diameter wood originating from young Scots pine (Pinus sylvestris L.) dominated stands. Pine pulpwood is the most harvested and most used roundwood assortment, use of which is expected to rise following new pulp-mill investments in Finland. In addition, utilisation of small-diameter trees directly for energy purposes has been increasing steadily in recent years. The aim of the study was to determine the cost-reduction potential of alternative forest management options and supply chains for small diameter-wood in the regional case of South Savo in eastern Finland. The total costs of three distinct scenarios were studied on the basis of forest management, first-thinning harvesting methods, and transportation: 1) industrial wood, 2) delimbed energy wood, and 3) whole trees for energy purposes. The cost-reduction potential for energy-wood supply chains from first thinning was compared to the industrial supply chain. Small-diameter delimbed wood delivered straight for energy purposes was found to be the most cost-efficient as far as the total cost of the supply chain is concerned. More cost-efficient small-diameter wood processes can be found by linking forest stand simulations with supply chain analysis.
article id 1428, category Research article
Effect of multi-tree handling and tree-size on harvester performance in small-diameter hardwood thinnings. Silva Fennica vol. 50 no. 1 article id 1428. https://doi.org/10.14214/sf.1428
Highlights: Harvesting with the accumulating energy wood head EF28 was studied under small tree dimension (8 dm3) in hardwood thinnings; Reasonable productivity was achieved; Maximum achieved cutting diameter in hornbeam stand was 23 cm and 15% lower than in softwood stands; Head has potential under such conditions.
Early thinnings are laborious and costly. Thus forest companies are searching for cost and time efficient ways to carry out this task. The study’s purpose was to determine the productivity of the EF28 accumulating energy wood harvesting head in harvesting small-diameter hornbeam (Carpinus betulus L.) undergrowth trees and evaluate the effect of its multi-tree handling (MTH) capacity on time consumption. The harvester was a wheeled, three-axle Komatsu 911. A time study of 7.1 hours on 19 plots, with a total area of 0.76 ha was conducted. On average, the harvested tree volume was 8 dm³ and the stand density was 2666 trees/ha. The productivity was modelled with MTH conduction, mean diameter at breast height and the number of trees handled per cycle as independent variables. On average, MTH took 27% longer per cycle, increased extracted volume per cycle by 33% and consequently increased productivity with 5.0%. In 71.9% of the cycles more than one tree was handled and if so, dimensions were smaller than in single-tree handling (5.8 cm vs. 12.0 cm). Maximum felling diameter of 23 cm was about 15% smaller than in softwood (according to the manufacturer’s specifications) and the driver didn’t exploit the EF28’s theoretical potential in terms of trees handled per cycle. It can be concluded that the head could significantly improve productivity in small-diameter wood procurement.
article id 1124, category Research article
Height increment of hybrid aspen Populus tremuloides x P. tremula as a function of weather conditions in central part of Latvia. Silva Fennica vol. 48 no. 5 article id 1124. https://doi.org/10.14214/sf.1124
Highlights: Intra-annual height growth of hybrid aspen was monitored; Clones with early leaf flushing dates showed faster height growth; Height growth was generally controlled by temperature; Fast-growing hybrids were more robust to weather conditions than slow-growing ones; Potential evapotranspiration (moisture regime) negatively affected height growth of clones with delayed phenology.
Height growth of young hybrid aspen (Populus tremula L. × P. tremuloides Michx.) was studied in relation to weather conditions. Height of clones with different leaf flushing phenology (early, intermediate and late) was monitored during the growing periods of 2010 and 2011 in a plantation established on former agricultural land. Mean daily height increment (HI) was calculated. Multiple linear regression was used to determine which weather factors (variables) had significant effect on HI. Mean seasonal height growth (mean seasonal HI) between clones (groups) was compared by ANOVA. In both years, HI was significantly higher for clones with early and intermediate leaf flushing compared to clones with late leaf flushing. The effect of weather factors also differed between clones according to their leaf flushing phenology; it was the weakest for HI of clones with early leaf flushing compared to clones with intermediate and late leaf flushing. Mean temperature was the main factor, which positively affected HI of all clones, suggesting that warmer climate might be beneficial for height growth of young hybrid aspen in Latvia. Nevertheless, significant negative relationship between HI and potential evapotranspiration (PET) was observed for clones with delayed leaf flushing, suggesting negative effect of increasing variability of precipitation on growth. Thus, the differences in height growth intensity might be related to growth sensitivity to weather conditions. On the other hand, such differences in height growth between clones might be caused by competition (i.e. with herbs), as trees with early leaf flushing might conquer more resources and become more robust against the environmental fluctuation.
article id 134, category Research article
Comparison of boom-corridor thinning and thinning from below harvesting methods in young dense Scots pine stands. Silva Fennica vol. 44 no. 4 article id 134. https://doi.org/10.14214/sf.134
At present, only a small proportion of the potential extractable bioenergy from young dense forests in Sweden is utilized. The conventional mechanized first thinning systems used in such stands suffer from low productivity, so the operation is only profitable in stands with bigger trees and high standing volumes. Conventional harvesters are used for this operation equipped with accumulating felling heads designed for handling several trees during each crane cycle. In thinning from below the felling and bunching work requires many time-consuming non-linear crane movements to avoid felling or damaging of future crop trees. However, higher productivity can be achieved when trees between strip roads are harvested in about 1 m-wide corridors with a length corresponding to the reach of the crane. We refer to this operation as boom-corridor thinning. The objective of this study was to compare felling and bunching productivity in young dense stands when employing thinning from below or boom-corridor thinning. Experiments were performed using a randomized block design involving between 4400 and 18 600 trees x ha-1 with a corresponding average tree size of 7.2 and 3.2 cm dbh, respectively. Based on the average tree being removed at a dbh of 5.7 cm, the productivity (ODt x PW-hour-1) was significant (almost 16%) higher for the boom-corridor thinning than for thinning from below treatment. At the same time, the time taken for the work element “Crane in-between” (the period between the loaded crane starting to move towards a tree and the felling head rapidly slowing down for positioning) was significantly reduced, by almost 17%. The positive results were achieved even though the operator was new to the method. To achieve a significantly higher efficiency during the felling and bunching operation, development of new harvesting equipment and operating techniques seems crucial.
article id 144, category Research article
Analyzing the views of wood harvesting professionals related to the approaches for increasing the cost-efficiency of wood harvesting from young stands. Silva Fennica vol. 44 no. 3 article id 144. https://doi.org/10.14214/sf.144
A lot of viable guidelines are currently available for more cost-effective harvesting of energy wood and industrial roundwood (i.e. pulpwood) from young stands. The study ranked the proposed potential approaches for increasing the cost-efficiency of small-diameter (d1.3 < 10 cm) energy wood and industrial roundwood harvesting from early thinnings. Research data, based on a total of 40 personal interviews, was collected in early 2008. The interviewees were divided into four wood harvesting professional groups: 1) Managers in wood procurement organizations, 2) Forest machine contractors, 3) Forest machine manufacturers and vendors, and 4) Wood harvesting researchers. In the opinion of the respondents, there is great potential to increase the cost-efficiency of wood harvesting through improving harvesting conditions (i.e. effective tending of seedling stands, delaying harvesting operations, and pre-clearance of dense undergrowth). The interviewees also underlined that harvesting methods can be rationalized, e.g. multiple-tree handling in industrial roundwood cuttings, crane scale measurement, integrated wood harvesting, and careful selection of stands for harvesting. The strong message given by the interviewees was that the education of forest machine operators must be made more effective in the future. There would be significant possibilities for cost savings in young stands, if methods and techniques with the most potential were utilized completely in wood harvesting.
article id 464, category Research article
Regional energy wood logistics – optimizing local fuel supply. Silva Fennica vol. 43 no. 1 article id 464. https://doi.org/10.14214/sf.464
The promotion of electric energy production from solid biomass by the Austrian government has lead to a boom in the construction of new combined heat and power plants. The current total demand for wood chips in the research area for energy purposes is 70 400 m3 of loose volume chips per year. The expected increase in demand due to these new plants is more than 4 times greater than current demand: up to 302 700 m3 of loose volume per year. Even if the energy wood feedstock potential is satisfactory, the design of the supply chain is still unresolved. The aim of this study is to give decision-makers a base for further development. To accomplish this, we designed and tested four different supply scenarios: one for 9 plants and one for 16 plants. The scenarios were developed using a combination of geographic information systems (GIS) and linear programming methods. The results indicate that direct transport of solid fuel wood as round wood and chipping at the plant is the cheapest supply system with a resulting cost of 5.6–6.6 EUR/m3 loose. Using harvesting residues can only be recommended for large plants because of poor fuel quality. In this case, residues would be chipped at or near the landing, piled and transported via self-loading trucks at a cost between 8.4 and 9.1 EUR/m3 loose. In order to meet increasing demand and to ensure a continuous supply, especially during the winter and spring seasons it is necessary to optimize the supply chain by including storage terminals. However, using terminals and increased demand both lead to higher logistical costs. For example, if the total volume is handled via terminals, the average supply costs including storage will increase by 26%. Higher demand increases the costs by 24%.
article id 220, category Research article
Energy wood thinning as a part of stand management of Scots pine and Norway spruce. Silva Fennica vol. 43 no. 1 article id 220. https://doi.org/10.14214/sf.220
The effects of combined production of industrial and energy wood on yield and harvesting incomes, as well as the feasibility of energy wood procurement, were studied. Data for 22 Scots pine (Pinus sylvestris L.) and 21 Norway spruce (Picea abies (L.) Karst.) juvenile stands in Central and Southern Finland were used to compare six combined production regimes to conventional industrial wood production. The study was based on simulations made by the MOTTI stand simulator, which produces growth predictions for alternative management regimes under various site and climatic conditions. The combined production regimes included precommercial thinning at 4–8 m dominant height to a density of 3000–4000 stems ha–1 and energy wood harvesting at 8, 10 or 12 m dominant height. Combined production did not decrease the total yield of industrial wood during the rotation period. Differences in the mean annual increment (MAI) were small, and the rotation periods varied only slightly between the alternatives. Combined production regime can be feasible for a forest owner if the price of energy wood is 3–5 EUR m–3 in pine stands, and 8–9 EUR m–3 in spruce stands. Energy wood procurement was not economically viable at the current energy price (12 EUR MWh–1) without state subsidies. Without subsidies a 15 EUR MWh–1 energy price would be needed. Our results imply that the combined production of industrial and energy wood could be a feasible stand management alternative.
article id 256, category Research article
Harvesting technology and the cost of fuel chips from early thinnings. Silva Fennica vol. 42 no. 2 article id 256. https://doi.org/10.14214/sf.256
This study compared and analyzed the procurement cost of whole tree chips when using supply chains based on comminution at the roadside landing or at the terminal. It also identified the bottlenecks of the most common logging systems used in Finland. The study was done by using existing and published productivity parameters and models. The procurement cost calculations were made for a stand where the forwarding distance was 200 metres, removal of whole trees was 60 m per hectare and the area of the stand was 2.0 hectares. The average size of the removed whole trees was 30 litres. The direct transport distance from the stand to the terminal or to the end use facility was 40 km while the secondary distance from the terminal to the end use facility was 10 km. A stumpage price for the harvested raw material was not included in this study. According to the study the cost of whole trees chips were 31.9–41.6 euros/m at the plant, or 14.9–19.4 euros/MWh when the moisture content of chips was estimated to be 40%. The two-machine system was found to be the most cost competitive logging system in pre-commercial thinnings thanks to both efficient cutting and, especially, forwarding work. In the manual worker based logging, the costs of felling bunching were the same as the mechanised system, whereas in forwarding the costs were almost double. Using the harwarder system the logging costs were found to be the highest, but in the larger tree volumes and removals the costs were almost equal to the manual worker based logging. The supply chain based on chipping at the roadside landing was more cost efficient compared to the chipping at the terminal system. The lower comminution cost at the terminal was not enough to cover the higher transportation cost of unprocessed material to the terminal, handling cost of chips at the terminal or the delivery cost to the end use facility.
Category: Research note
article id 470, category Research note
Energy wood and pulpwood harvesting from young stands using a prototype whole-tree bundler. Silva Fennica vol. 41 no. 4 article id 470. https://doi.org/10.14214/sf.470
The productivity of cutting and bundling whole trees using the first prototype of a bundle-harvester comprised of a harwarder as the base machine, an accumulating felling head, and a compacting device was studied in three young stands in order to facilitate the further development of the concept. In addition, the removal and its composition were studied as a means of laying the foundations for developing methods for work rating and measurement on delivery. Bundling enables in-depth integration of pulpwood and energy wood procurement. Both energy wood (crown biomass) and pulpwood can be incorporated into the same bundles, and the subsequent separation of these fractions takes place at the debarking phase at the pulpmill. Bundle-harvesting productivities were relatively low (2.8–3.7 m3/E0-h) when compared to current harvesting technology. Improving working techniques, machine structure, and components showed great potential for increasing the efficiency of the concept. The bundles were dimensionally uniform. Their solid volume varied between 0.350 m3 and 0.513 m3, depending on the bundle assortment and stand properties. Integrating energy wood harvesting with pulpwood harvesting increased removal even by 59 per cent.