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Volume 40 No.2

Cost Analysis of Innovative Biomass Harvesting Systems for Young Dense Thinnings

volume: 40, issue:

The objective was to analyze three innovative harvesting systems for early thinnings and compare forest-to-industry supply costs. FlowConv consists of a harvester equipped with an innovative continuously cutting, accumulating and bunching head (the FlowCut head), a forwarder and a truck to transport loose tree-parts. FlowFix consists of a harvester equipped with the same cutting head but also a bundling unit (the Fixteri system), plus a forwarder and roundwood truck for biomass transport. FlowCin consists of a new conceptual biomass harvester (the Cintoc system) equipped with the same cutting head and a second crane to pass the cut trees from the front of the machine to a bundling unit at the back, plus the same forwarding and trucking units as in the FlowFix system. Empirical data were used to assess the FlowConv system’s performance, while the FlowFix and FlowCin systems’ performance was simulated.

Results indicate that supply costs of the FlowCin system would be 6–10% and 24–29% lower than those of the FlowFix and FlowConv systems, respectively. Thus, it would be more suitable to be equipped with an innovative cutting head, which is up to 100% more efficient than the current commercially available options. Key features of the Cintoc-based system (which minimize possible waiting times during operation) include its buffering cradle and delivery of biomass acquired in two cutting crane cycles to the intermediate delivering crane. The apparent superiority of the FlowCin system is consistent with previous conclusions regarding developments needed to maximize the cost-effectiveness of harvesting young dense stands.

Biomass Yield and Fuel Properties of Different Poplar SRC Clones

volume: 40, issue:

The goal of the research was to determine the biomass yield and fuel properties of ten different poplar clones. The research was conducted in an experimental plot established in Forest Administration Osijek, Forest Office Darda, in the spring of 2014. The layout of the plot consisted of three repetitions per clone with 40 plants per repetition in spacing 3x1 m. Based on the DBH distribution, in the early spring of 2018, one sample tree of an average DBH per repetition was selected, thus forming a sample of 30 trees.

Average survival rate of the investigated trees after four vegetation periods was 74.54 ±13.85% ranging from 52.08% (Koreana) to 91.67% (SV885 and SV490). Average DBH of the sample trees was 8.2 ±1.9 cm, height 9.3 ±1.8 m and root collar diameter 10.7 ±1.9 cm. Moisture content in fresh state (just after the felling) ranged from 51.6% (Hybride 275) to 55.9% (SV885). Bark content averaged 18.4%, from 15.4% (Baldo) to 21.1% (V 609). Average nominal density of the sampled trees amounted to 383.5 ±35.9 kg/m3. Bark ash content was on average ten times higher (6.44 ±0.65%) than wood ash content (0.64 ±0.07%) resulting in average ash content of 1.7 ±0.1% (taking the bark content into account).

The clone SV490 showed the highest biomass yield with 15.8 t/ha/year, while the lowest biomass yield was recorded for the clone Hybride 275 with 2.8 t/ha/year.

High inter-clonal productivity variation stresses the importance of selection work to find the most appropriate clones with the highest productivity potential for the given area where the poplar SRC plantations are to be established.

Due to high initial moisture content, if direct chipping harvesting systems are preferred, wood chips could be efficiently used in CHP (Combined Heat and Power) plants that operate on the principle of biomass gasification (where a gasifier is coupled to a gas engine to produce electric power and heat). In several CHP gasification plants operating in Croatia, wood chips with high initial moisture content (from traditional poplar plantations) are used as a feedstock that has to be pre-dried using the surplus heat. In this respect SRC poplar wood chips could make an ideal feedstock supplement.

Selected Environmental Impacts of Forest Harvesting Operations with Varying Degree of Mechanization

volume: 40, issue:

Climate change affects forest ecosystems, impacting timber production and eco-services. Conversely, sustainable forest management has been identified as a means to help mitigate carbon dioxide emissions, a greenhouse gas and contributor to climate change, while also maximizing multiuse benefits through close-to-nature silviculture. In this study, a life cycle assessment was performed on forest harvesting operations at three research sites to provide real-world understanding of the selected environmental impacts associated with harvesting systems typical of Germany: motor-manual (chainsaw and forest tractor), semi-mechanized (single-grip harvester, chainsaw, and forwarder), and fully-mechanized (single-grip harvester and forwarder). Environmental impact categories assessed included greenhouse gas emissions, particulate matter emissions, and non-renewable energy consumption. Results from the three research sites were estimated on a machine basis. The semi-mechanized system resulted in the lowest environmental impact, the majority of which was attributed to felling and processing operations. Next, the environmental impacts were estimated for a complete rotation period and compared amongst the different harvesting systems. According to results, semi-mechanized harvesting systems had the lowest impact over the full rotation period as well as for thinning treatments when compared to motor-manual and fully-mechanized systems. The fully-mechanized system performed the best for final felling treatments. Considering variability between the research sites as well as the system boundary assessed, a diversified approach to harvesting operations may be considered, integrating semi-mechanized and fully-mechanized systems for different treatments throughout the rotation period.

What Do We Observe When We Equip a Forestry Crane with Motion Sensors?

volume: 40, issue:

Forestry machines have the power to efficiently move very heavy loads, but they are not very smart at communicating information, especially information regarding motion. Understanding how a system produces motion is one of the main stepping stones towards the world of automation. However, to acquire motion data requires sensor hardware that is not largely available in forestry machines today. As a result, at the moment there is no motion data analysis for forestry machines. Therefore, the objective of this article is to present this data, and discuss how we can use such data in regards to technology development. To this end, we have equipped a commercial forestry machine with state-of-the-art sensors and a data acquisition unit. Our aim is to understand what possibilities exist for automation, when we analyze how machine operators control forestry cranes. Among our objectives is to show how motion data can: a) give a better comprehension of the way forestry operators control cranes, b) be useful to analyze crane motion patterns, and c) show additional information that can be estimated via mathematical algorithms. The topics we cover only touch the surface of future applications, where sensor data analysis will be able to team up with other technologies to improve operator’s work, including automation, decision making, motion optimization, and operators’ training, just to mention some.

Assessing Cable Tensile Forces and Machine Tilt of Winch-Assisted Forwarders on Steep Terrain under Real Working Conditions

volume: 40, issue:

Winch-assisted forwarders are now commonly accepted as an innovative alternative for extracting wood on challenging terrain. In order to assess safety risks, it is necessary to know the tensile forces in the steel wire rope and their interaction with the machine tilt under real working conditions. In this study, the tensile force and the machine tilt of two winch-assisted forwarders (John Deere 1210E and Komatsu 840TX) were observed for about 15 work hours without delays on two different stands in Austria. The tensile force data and the machine tilt data were separated by work elements. The mean tensile force ranged from 18.1 kN for unloading up to 56.8 kN for loading activities. During the measurements, the cable tensile force exceeded 50% of the minimum breaking strength (MBS) only twice. The maximum observed tensile force was 174.5 kN or 82.7% of the MBS, respectively, which led to a failure of the steel cable. For the machine tilt, a maximum of 80% was measured during loading and driving during loading. John Deere 1210E was operated 31% of the productive work time above the manufacturers tilt limit. For Komatsu 840TX, the manufacturers’ maximum tilt limit was exceeded only twice. The study also showed that peaks with an amplitude of up to 50 kN can occur within a few centiseconds, which highlights the need of high measurement rates, when measuring cable tensile force of winch-assisted machinery. The detailed analysis of the peaks showed that 90% of the pit-to-peak amplitudes ≥20 kN occurred during driving activities. Only 10% of pit-to-peak amplitudes ≥20 kN were measured during loading activities, although loading took about 43.5% of the productive work time. As such, the study results confirm that amplitudes of peaks in tensile force, and hence safety risks, are significantly higher during driving than during loading.

Simulation Modeling of Truck Load of Skidding Tractors with a Grapple for Chokerless Skidding

volume: 40, issue:

The objective of the present study is to define mass distribution laws for a bundle of trees using the methods of statistical simulation modeling in order to calculate chokerless skidding tractors lift capacity. For that purpose a statistical simulation model has been developed to generate forest taxation data necessary for complete filling of skidding tractor grapple. The following samples have been obtained from the regions of the European North of Russia based on the model: masses of bundles of trees that can be placed in grapple and values of vertical component of normal load applied to skidding tractor grapple. Minimum values for masses of bundles may vary in the range of 40–87% from the average value. Maximum values may vary in the range of 8–55% from the average value. The difference between the maximum and minimum masses of bundle values increased with increasing the capacity grapple and decreased with increasing the distance from the butt to grapple. We have determined the dependence of bundle mass variation and values of vertical component of normal load applied to skidding tractor grapple on capacity grapple for the regions of the European North of Russia. The studies have allowed determining recommended values for chokerless skidding tractors lift capacity. The analysis of specifications of various models of skidding tractors has shown that clambunk skidders have deficient marginal lift capacity.

Productivity of a Portable Winch System Used in Salvage Logging of Storm-Damaged Timber

volume: 40, issue:

Storm damages result in serious losses in many regions, primarily by stem breakage or blowdown. Extraction of storm-damaged trees often requires more difficult than normal skidding activities due to obstacles created during the storm. In this study, the productivity of a portable winch was evaluated as a possible alternative to recover storm-damaged timber. Field measurements were conducted in the Alabarda Forest Enterprise Chief located near the city of Kütahya in western Turkey, where storm damage often occurs during the winter season. The time study was implemented in two slope classes (35% and 55%) and two skidding distances (40 m and 60 m). All timber was skidded uphill. A regression mode was developed that related productivity to log volume, ground slope and skidding distance. The highest percentage of total cycle time was observed for skidding logs to the landing. The highest productivity (3.96 m3/hour) was found at the shorter skidding distance (40 m) and the lower ground slope (35%). Statistical analyses indicated that productivity was most highly affected by log volume, followed by skidding distance and ground slope. Larger log loads increased productivity, while both longer skidding distances and steeper slopes reduced productivity.

Evaluation of Different Best Management Practices for Erosion Control on Machine Operating Trails

volume: 40, issue:

Ground-based mechanized forest operations often lead to increased runoff and soil loss on unbound forest roads and machine operating trails, which in turn can impede the technical trafficability of machines and cause negative impacts on the environment. The aim of this study was to evaluate the effectiveness of three Best Management Practice (BMP) treatments used to control erosion occurring on machine operating trails. The treatments included water bar, water bar and hardwood brush (H-brush), and water bar and softwood brush (S-brush). For a more comprehensive assessment of both brush treatments, two levels of brush thickness were tested; 0.5 m and 1.0 m. Results indicate that the most effective BMP treatments were the water bar and softwood brush followed by the water bar and hardwood brush and finally the least effective was the water bar. The average runoff rates and soil loss from the machine operating trails with the water bar treatment (52.64 l per plot, 8.49 g m-2) were higher than runoff and soil loss at the trails protected with hardwood brush (23.75 l per plot, 4.5 g m-2), and the trails protected by the hardwood brush had higher runoff and soil loss compared to trails covered by softwood brush (15.83 l per plot, 2.98 g m-2). Furthermore, results of this study showed that regardless of the treatment, the amount of runoff and soil loss decreased consistently as the thickness of the brush mat increased. Overall, erosion control techniques similar to either H-brush or S-brush that provide direct soil coverage should be used for erosion control, and final selection should be based on costs, availability of material, or landowner objectives.

Using Wood-Shred, Rice-Straw and Brush-Wood-Dams with Planting Seedlings to Runoff and Erosion Control in a Forest Road Fill Slope

volume: 40, issue:

This study aimed to investigate the effects of two types of natural geotextiles, including wood shred (WS), rice straw (RS) and the biomechanics method of brush wood dam (BWD) with planting seedlings of Alnus glutinosa and Salix alba on runoff, soil loss and fill slope. The effects were compared with those obtained from control treatment. A total of 36 plots (2×4m) with three replicates in the direction of gradient to fill slope of a forest road in northern Iran was considered. Soil moisture, canopy cover of seedlings, vegetation coverage, runoff, sedimentation and erosion were measured in plots during 12 months. BWD and WS played an effective role in reducing runoff by 57% and 73%, respectively. By using RS and WS,  the sediment concentration was decreased by 23% and 11%, respectively, while by using BWD it increased by 58%. RS (24.16%) and BWD (7%) had the greatest and smallest impact on reducing vegetation coverage, respectively. BWD (33%) and RS (27%) had the highest and lowest canopy cover of seedlings, respectively. Results showed that both RS (22.23%) and A. glutinosa (4.96%) had the greatest effects on increasing soil moisture. Comparison between the planted species and the control treatment (with no seedlings) showed that S. alba was effective in reducing runoff (46.22%), while A. glutinosa was effective in reducing erosion (66.89%) and sediment concentration (53.52%). Finally, interactions between conservation treatment and planting of seedlings played a more effective role in controlling runoff and erosion. Therefore, the application of conservation treatments together with planting of seedlings is recommended in order to provide better soil conservation and restoration of fill slope.

Effects of Ground-Based Skidding on Soil Physical Properties in Skid Trail Switchbacks

volume: 40, issue:

Effective skid-trail design requires a solid understanding of vehicle-soil interactions, yet virtually no data exist on the effects of harvest traffic on soils in the switchback curves common in mountainous terrain. We contrast for the first time the effect of skidding on dry bulk density, total porosity, macroporosity, and microporosity in the straight segments of the skid trail and in various positions within switchbacks of differing trail curvature (deflection angle) on different slope gradients. Treatment plots with three replications included combinations of two classes of curvature (narrow = high deflection angle, 60–70°; wide = low deflection angle, 110–130°) and two categories of slope gradient (gentle = ≤20%; steep = >20%). The Cambisol soil was sampled in control and trafficked areas both before and after three passes with a rubber-tired skidder. After only three passes, significant effects were seen for dry soil bulk density (+), total porosity (–), macroporosity (–), and microporosity (+), with steady trends from undisturbed controls to straight segments to wide curves to narrow curves. Soil damage increased gradually and consistently toward the apex of the curve, particularly in narrow curves on gentle slopes. Our results establish that curvature and switchback position are important factors affecting soil compaction in ground skidding. The strong observed effects of even low harvest traffic volume on soil physical properties in curves indicate that the degree of soil compaction in skid trails may be underestimated in areas with numerous switchbacks, the placement of which within a skid trail system may require careful consideration on mountainous terrain.

Addressing Occupational Ergonomics Issues in Indonesian Forestry: Laborers, Operators, or Equivalent Workers

volume: 40, issue:

This study addresses occupational ergonomics issues in Indonesian forestry (work conditions, workers' characteristics, occupational safety, occupational health, and job satisfaction) to acquire a comprehensive perspective in understanding the actual problems facing the operations. Direct observation, interview, questionnaires, and secondary data analyses were carried out to acquire all of the required information. A total of 191 frontline forestry workers (chainsaw operators, helpers, manual hauling workers, skidder/tractor operators, logging truck drivers, and nursery workers) participated in this study. The study shows that various techniques of forest operations (labor-intensive to semi-mechanized systems) have been applied in Indonesian plantation forests, both short and long-rotation, as well as in natural forest management. Most of the workers were non-permanent workers, who receive a low wage, work under a straight piecework system, have a high dependency on the forestry work to make a living, and exhibit poor comprehension of the concept of hazard control. The fatality rate was recorded as 1.3 deaths/106 m3 log, but this may be even higher as this rate only represents data taken from formal forestry workers. An intense physical dimension of fatigue occurs among workers involved in forest operations, with the highest prevalence of musculoskeletal disorders in the upper back, lower back, neck, shoulders, and arms. This study reveals eight variables that influenced job satisfaction, i.e., wage, type of contract, accessibility, health services, living facilities, work equipment, training, and social facilities.

Assessment of Broad-Leaved Forest Stand Management: Stock Densities, Thinning Costs and Profits over a 60-Year Rotation Period

volume: 40, issue:

There are many broad-leaved forests in Japan that were formerly managed for charcoal production, which have been abandoned for decades. Appropriate thinning can revitalize these forests if the cost balance of the management is positive. Two critical elements are the construction of spur roads to facilitate mechanized harvesting operations and management planning that considers stand properties such as the growing stock, species, and tree size distribution. We surveyed three abandoned former broad-leaved coppice stands; one coastal, one cool temperate and one warm temperate. The stock in all three stands exceeded 300 m3 ha-1, two- to three-fold the official forest registry data estimates. The dominant species in terms of tree numbers are Castanopsis sieboldii, Pieris japonica, and Quercus glauca. Medium-sized trees involve those well suited for firewood, i.e., Quercus acuta, Quercus glauca, Quercus serrata, etc. Each plot contained a few large trees that potentially have a high market value, e.g., Cinnamomum camphora, Zelkova serrata, Abies firma, etc. The average income from harvested trees was estimated to be 10200 JPY (Japanese Yen) m-3, whereas the thinning costs would be 3200 to 5400 JPY m-3, with the additional spur road construction costs. The management cost balance of a broad-leaved stand in a 60 year rotation was evaluated with both Net Present Value (NPV) (for interest rates of 1, 2, 3, and 4%) and Internal Rate of Return (IRR). This balance was compared with that of a typical plantation stand of Japanese cedar (Cryptomeria japonica) and of a fast-growing plantation stand of Chinese fir (Cunninghamia lanceolata). The estimated NPVs were largest for the fast-growing plantation stand, second largest for the typical plantation stand, and lowest for the broad-leaved stand with a NPV interest rate of 1 + %. However, the IRR of the broad-leaved stand was the highest, followed by that of the fast-growing plantation stand, while the IRR of the typical plantation stand was the lowest. This order was the same for NPVs assuming higher interest rates.

1 JPY=0.0086 € on April 29, 2019.

Physical Strain, Exposure to Noise and Postural Assessment in Motor-Manual Felling of Willow Short Rotation Coppice: Results of a Preliminary Study

volume: 40, issue:

Biomass for energy production and other bioproducts may be procured from various sources including willow short-rotation coppice (WSRC). Management of WSRCs involves several operations, including harvesting, which accounts for the greatest cost share and, if conducted motor-manually, it can expose the workers to noise, uncomfortable work postures and high cardiovascular loads. In this study, we evaluated the productivity, physical strain, exposure to noise, and postural risk index of workers operating in motor-manual felling of WSRC using a set of automatic dataloggers. Productivity of felling operations was rated at 0.07 ha/h, which is in line with the results reported by other studies. Cardiovascular load was rated at cca. 35% of the HRR, indicating a medium to heavy work experienced by the feller, with a greater contribution of tasks involving movement. Exposure to noise (LEX,8h = 95.19) exceeded the limit value set by the European legislation (87 dBA) and it could increase as a function of the engine utilization rate, which was 68% in this study, advocating for mandatory wearing of protective equipment. Postural risk index was evaluated at 191.11% for the worker handling the brush cutter and at 192.02% for the manual assistant indicating rather reduced risks, but also the need to evaluate how the dynamic work of the upper limbs would affect the workers’ health. While this work stands for a preliminary case study, the procedures described may be successfully used to easily collect long-term data in such operations.

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Web of Science Impact factor (2019): 2.500
Five-years impact factor: 2.077

Quartile: Q1 - Forestry

Subject area

Agricultural and Biological Sciences

Category/Quartile

Forestry/Q1