Andrew McEwan, Natascia Magagnotti, Raffaele Spinelli. (2016). The effects of number of stems per stool on cutting productivity in coppiced Eucalyptus plantations. Silva Fennica vol. 50 no. 2 article id 1448. https://doi.org/10.14214/sf.1448

Keywords: modeling; logging; short rotation forestry; efficiency; operator effect

Highlights: Double- and single stem coppice stools were harvested mechanically; Stem size had the strongest impact on productivity; An experienced operator performed equally well with both stool treatments; Cost was ~10% higher with double stems for the less experienced operator; Operator experience may play a major role when cutting coppice stands.

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A time study was conducted to determine whether stem crowding had any impact on harvester productivity in Eucalyptus grandis stands. This represents an important element when trying to balance the advantages and disadvantages of coppice management in fast growing plantations designated for mechanized harvesting (i.e. machine felling, delimbing, debarking and cross-cutting). The study material consisted of 446 coppice stems, half of which grew as single stems per stool and half as double stems per stool as a result of different coppice reduction strategies. The dataset was balanced and randomized, with both subsets replicating exactly the same stem size distribution and the single and double stems alternating randomly. Harvester productivity ranged between 6 and 50 m³ under bark per productive machine hour, following the variation of tree diameter from 10 to 40 cm at breast height (1.37 m according to South African standards). Regression analysis indicated that both tree size and stem crowding (e.g. one or two stems per stool) had a significant effect on harvester productivity, which increased with stem size and decreased with stem crowding. However, operator experience may overcome the effect of stem crowding, which was not significant when the harvester was manned by a highly experienced operator. In any case, the effect of stem size was much greater than that of stem crowding, which resulted in a cost difference of less than 10%. However, this figure excludes the possible effects of stem crowding on volume recovery and stem development, which should be addressed in the future.

McEwan, Nelson Mandela Metropolitan University – George Campus, Saasveld, 6529, George, South Africa E-mail: Andrew.McEwan@nmmu.ac.za
Magagnotti, CNR IVALSA, Via Madonna del Piano 10, I-50019 Sesto Fiorentino (FI), Italy E-mail: magagnotti@ivalsa.cnr.it
Spinelli, CNR IVALSA, Via Madonna del Piano 10, I-50019 Sesto Fiorentino (FI), Italy E-mail: spinelli@ivalsa.cnr.it

article id 1342, category Research article

Blas Mola-Yudego, Gianni Picchi, Dominik Röser, Raffaele Spinelli. (2015). Assessing chipper productivity and operator effects in forest biomass operations. Silva Fennica vol. 49 no. 5 article id 1342. https://doi.org/10.14214/sf.1342

Keywords: mixed models; efficiency; comminution; operator effect; raw material supply; wood chippers

Highlights: A model is constructed to assess the productivity in chipping of wood biomass at roadside; The data includes 172 trials and 67 operators in Italy; The operator effect was included in a mixed model approach; The R2 were 0.76 (fixed part) and 0.88 (incl. operator effects).

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The present research focuses on the productivity of energy wood chipping operations at several sites in Italy. The aim was to assess the productivity and specifically the effect attributed to the operator in the chipping of wood biomass. The research included 172 trials involving 67 operators across the country that were analysed using a mixed model approach, in order to assess productivity, and to isolate the operator effect from other potential variables. The model was constructed using different predictors aiming to explain the variability due to the machines and the raw-materials. The final model included the average piece weight of raw material chipped as well as the power of the machine. The coefficients of determination (R²) were 0.76 for the fixed part of the model, and 0.88 when the effects due to the operators were included. The operators’ performance compared to their peers was established, and it was compared to a subjective classification based on the operator’s previous experience. The results of this study can help to the planning and logistics of raw material supply for bioenergy, as well as to a more effective training of future forest operators.

Mola-Yudego, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland; NIBIO Norwegian Institute of Bioeconomy Research, P.O. Box 115, 1431 Ås, Norway http://orcid.org/0000-0003-0286-0170 E-mail: blas.mola@uef.fi
Picchi, CNR IVALSA, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy E-mail: picchi@ivalsa.cnr.it
Röser, Forest Feedstocks Group, FPInnovations, Vancouver, British Columbia, Canada E-mail: dominik.roser@fpinnovations.ca
Spinelli, CNR IVALSA, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy E-mail: spinelli@ivalsa.cnr.it

article id 227, category Research article

Ola Lindroos. (2008). The effects of increased mechanization on time consumption in small-scale firewood processing. Silva Fennica vol. 42 no. 5 article id 227. https://doi.org/10.14214/sf.227

Keywords: comparative time study; fuelwood; blade saw; wedge splitter; processor; senior worker; operator effects

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Firewood, which is mainly processed by the consumer, is still an important source of energy for heating houses in industrialised countries. Possibilities to compare the mechanization’s impact on efficiency of firewood processing are limited, due to variations between working conditions in previous studies. Therefore, the objective was to compare time consumption for two small-scale firewood processing systems with different levels of mechanisation under identical conditions. The systems were tested on two classes of wood: one with a homogeneous and medium-sized diameter of logs and one with a mixture of small and large-diameter-logs. Differences in time consumption were analysed for correlations with physical workloads, deviations to routine operations, operator influences and operator perceptions. Twelve operators (60–79 years old) were studied and they showed large variation in time consumption. However, the within-operator time consumption patterns were consistent. In other words, operators all responded similarly to the different combinations of systems and wood classes, but at different absolute levels. The time required to process a unit volume of wood was 25–33% lower when the more highly mechanised system was used, and the time required was 13–22% lower for the homogeneous wood class. Physical work load, deviations and perceptions of the work varied between operators, but were weakly correlated with time consumption. The results’ implications for analyses of investments in equipment for firewood-processing for self-sufficiency purposes are discussed.

Lindroos, Swedish University of Agricultural Sciences, Department of Forest Resource Management, SE-901 83 Umeå, Sweden E-mail: ola.lindroos@srh.slu.se

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