Abstract
The processing of Eucalyptus logs is a stage that follows the full tree system in mechanized forest harvesting, commonly performed by grapple saw. Therefore, this activity presents some associated uncertainties, especially regarding technical and silvicultural factors that can affect productivity and production costs. To get around this problem, Monte Carlo simulation can be applied, or rather a technique that allows to measure the probabilities of values from factors that are under conditions of uncertainties, to which probability distributions are attributed. The objective of this study was to apply the Monte Carlo method for determining the probabilistic technical-economical coefficients of log processing using two different grapple saw models. Field data were obtained from an area of forest planted with Eucalyptus, located in the State of São Paulo, Brazil. For the technical analysis, the time study protocol was applied by the method of continuous reading of the operational cycle elements, which resulted in production. As for the estimated cost of programmed hour, the applied methods were recommended by the Food and Agriculture Organization of the United Nations. The incorporation of the uncertainties was carried out by applying the Monte Carlo simulation method, by which 100,000 random values were generated. The results showed that the crane empty movement is the operational element that most impacts the total time for processing the logs; the variables that most influence the productivity are specific to each grapple saw model; the difference of USD 0.04 m3 in production costs was observed between processors with gripping area of 0.58 m2 and 0.85 m2. The Monte Carlo method proved to be an applicable tool for mechanized wood harvesting for presenting a range of probability of occurrences for the operational elements and for the production cost.
Highlights
In Brazil, commercial planting of forest species, mainly the genus Eucalyptus sp., is important from the economic perspective (3.7 million of jobs)
The total duration of the study was 13 hours and 20 minutes, which allowed the processing of 1466.80 cubic meters of wood
When weighing the grapple saw 1 (GS1), it was verified that the operational cycle average time was 96.94 seconds, due to 5.3 seconds demanded for picking up wood bundles (PWB), 26.3 seconds consumed for loading wood bundles (LWB), 15.6 seconds for processing logs (PLO) and 39 seconds required for crane empty movement (CEM)
Summary
In Brazil, commercial planting of forest species, mainly the genus Eucalyptus sp., is important from the economic perspective (3.7 million of jobs). They covers an area of 5.7 million hectares (BTI 2017), accounting for about 1% of the country’s gross domestic product (GDP). Under this perspective, the optimization of the mechanized forest harvesting operation, commonly used in Brazil, has paramount importance due to the capital necessary for providing the machinery, required for each forestry activity. The processing of whole trees is carried out after the extraction phase It aims at log processing in lengths, which varies mainly according to the transportation mode and to industrial processes. This operation can be performed by a grapple saw, which has been already tested in other experiments (Spinelli et al 2014, Spinelli et al 2019)
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