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Abstract

This paper uses Data Envelopment Analysis (DEA) to evaluate how the technical efficiency of forest harvesting operations is influenced by terrain conditions and forest attributes, in addition to exploring the existence of other influencing factors. To this end, 643 shift-level observations of harvesting operations on 253 distinct harvested sites were used. The aim of this study is to highlight the harvester’s ability to maximize the outputs, represented by the number of assortments for various tree species, given inputs such as harvest volume, harvest time for various tree species, and distance traveled by the harvester. Operational environment variables such as harvest, or decision-making unit (DMU) size, shape, and terrain characteristics were included. We found large variations in efficiency scores, and that inefficient harvest operations could theoretically be improved by reducing input by up to ca. 80%. A second stage regression estimation was applied to identify which factors significantly affected inefficiency. It was found that the inefficiency decreases with increasing stem-volume for pine and broadleaves, increasing stand density, and increasing share of pulpwood and non-marketable timber, while it increases with the number of logs produced per tree (in broadleaves). Inefficiency increases also with an increasing ratio of actual travel distance to minimal travel distance. The study shows how adopting DEA methods in forest operations might be used in combining efficiency analysis and environmental factors, by identifying and measuring inefficiency due to, for example, difficult terrain.

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Abstract

Integration of technology is commonplace in forestry equipment supporting higher levels of automation and efficiency. For technology adoption to be successful it must demonstrate improvement in productivity, cost–effectiveness or in human factors and ergonomics. Cable yarding lends itself to automation with repetitive machine movement along a fixed corridor, as established by the skyline. This study aimed at investigating the difference in productivity between the two possible settings (manual and automated) of a Valentini V850 yarder equipped with automatic path programming, with a Bergwald 3-t carriage and radio controlled chokers. The study took place in the northern Italian Alpine eastern region over a period of 8 days on two separate corridors, resulting in 280 measured cycles split between manual and automated. Results in terms of absolute numbers were very close for the two system options, but significant differences were found. For example, inhaul time was longer, but outhaul time shorter for the automated system. Productivity ranged from 8.2 to 13.3 m3 PMH-1, and cost from approximately 20 to 30 € m-3. The automated system did achieve a significantly higher productivity, but differences declined with extraction distance. When that was combined with the slightly higher cost for the automated system, the automated system was more cost-effective on extraction distances less than 200 m, and the manual system on longer distances.

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Abstract

The quality requirements of wood biofuels are regulated by a series of harmonized international standards. These standards define the technical parameter limits that influence the quality of solid biomass as a fuel. In 2014 the European reference standard for solid biofuel was replaced by the International ISO standard. In the case of wood chips, the main difference between the European and International standards is the definition of particle size distribution classes. In this context, this study analyses the quality of wood chips and its variation over the years according to the “former” (EN 14691-4) and “in force” (ISO 17225-4) standards. A Soft Independent Modelling of Class Analogy (SIMCA) model was built to predict the best quality of wood chips and to clarify the relationship between quality and standard parameters, time and changes in the standard regulations. The results show that, compared to the EN standards, classification with the ISO standards increases the samples belonging to the best quality classes and decreases the not classified samples. Furthermore, all the SIMCA models have a high sensitivity (>90%), reflect the differences introduced to the quality standards and are therefore suitable for monitoring the quality of wood chips and their changes.

Abstract

Winching is common in small-scale forest operations, especially on steep slopes, where tractors cannot reach the logs inside the forest. In this case, logs are dragged to the roadside with tractor-mounted winches, for later collection by transportation units. Winching is a heavy task, posing a high physiological stress on winching crew members. The aim of this study was to investigate the relationship between experienced workload, work conditions and operator fitness. The study confirmed the assumption that fit, young operators experience a lower workload than older ones. Workload depends on winching direction, and it is higher when winching downhill than when winching uphill. Results confirmed that gravity is the main factor, and it has a stronger effect than task type and tool weight. Walking uphill with no tools is heavier than walking downhill and carrying a steel cable. As a consequence, tool weight reduction can only palliate the problem, without solving it. Winching crews should be composed of fit, young workers. When the task is assigned to older workers, it is necessary to allow longer rest breaks, accepting a lower productivity. Keywords: steep terrain, winching, workload, heart rate

Abstract

This study presents the analysis of panel data on steep terrain logging productivity in Norway. Given the specification of a Cobb Douglas stochastic frontier production function in which the technical inefficiency is a function of six different environmental factors, it was found that only one (terrain hindrance) decreased the efficiency significantly. The estimated efficiencies for the sample crews ranged from 0.43 to 0.99. Because of the nature of the inefficiency factors, one way to improve the efficiency could be to train the crews for working on steep slopes. This would also improve the safety when exposing workers to these types of environmental hazards.

Abstract

This study examined the difference in workload brought about by exchanging a 3.5mm steel rope with a 4.0 mm synthetic fiber rope when dragging a strawline up a 300 m corridor in setting up a new cable-yarding line. Physiological workload was monitored through heart rate measurement, while the physical forces acting on the subject (rope mass and friction) were quantified using a dynamometer attached to a belt. While there was a substantial difference in force between rope types at full extent (140 N vs. 40 N), the result was less significant when seen against the total work required in moving the subjects own body mass up the slope. The direction of the resultant force vector appears to play an important role in the way that strain is experienced. It was discovered that 300 m was the maximum hauling distance for a single person using this rigging method with a steel wire strawline, whereas for the synthetic rope, the same tensile force would only be reached at 1200 m. This alone has important implications for labor saving amongst small cable logging teams.