Pierre Ackerman

The COST model for calculation of forest operations costs

Since the late nineteenth century when high-cost equipment was introduced into forestry there has been a need to calculate the cost of this equipment in more detail with respect to, for example, cost of ownership, cost per hour of production, and cost per production unit. Machine cost calculations have been made using various standard economic methods, where costs have been subdivided into capital costs and operational costs. Because of differences between methods and between national regulations, mainly regarding tax rules and subsidies, international comparisons of machine costs are difficult. To address this, one of the goals of the European Cooperation in Science and Technology (COST) Action FP0902 was to establish a simple format for transparent cost calculations for machines in the forest biomass procurement chain. A working group constructed a Microsoft Excel–based spreadsheet model which is easy to understand and use. Input parameters are easy to obtain or possible to estimate by provided rules of thumb. The model gives users a simultaneous view of the input parameters and the resulting cost outputs. This technical note presents the model, explains how the calculations are made, and provides future users with a guide on how to use the model. Prospective users can view the model in the Supplementary Material linked to this article online.

Multi-Stem Mechanized Harvesting Operation Analysis - Application of Arena 9 Discrete-event Simulation Software in Zululand, South Africa

Abstract Time studies were carried out on a stump-to-mill multi-stem Eucalyptus harvesting and transport operation in Zululand, South Africa in 2007. A simulation model (System 1) of this system was subsequently built using a commercial simulation software package (Arena 9) and data from the time studies incorporated into the model. Following this, two hypothetical stump -to-mill multi-stem models (Systems 2 and 3) were built using Arena 9 and parameterized input data. All models were found to adequately represent reality. Simulated harvesting system balance was improved through normalization of machine utilization in Systems 2 and 3. Production improvements were predicted with simulated timber production per month increasing by 31.1% and 30.8%, from System 1 with three trucks, to System 2 with four trucks, and System 3 with four trucks, respectively. Cost reduction was predicted, with the cost per unit of timber decreasing by 12.5% and 4.1%, from System 1 with three trucks, to System 2 with four trucks and System 3 with four trucks, respectively. Beneficial operational techniques were also confirmed using the simulation models. In the studied conditions delimbing and debarking of full trees into tree lengths at roadside with delimber-debarkers before cross-cutting and loading with a slasher was predicted to be

Effects of irregular stand structure on tree growth, crown extension and branchiness of plantation-grown Pinus patula

0.65/m3 cheaper than delimbing, debarking, and cross-cutting full trees into pulpwood with processors at the landing and then loading with a loader. Usability of Arena 9 in modeling forest harvesting operations was concluded as acceptable, but required detailed background logic inclusion.

Biomass from Wood in the Tropics

The practice of combining row and selective thinning in commercial pine plantation silviculture carries the risk of unwanted irregularities in tree distribution, a situation that is aggravated when tree selection during marking is poor. The potential consequences of poor tree selection are accentuated by gaps along row removal. This leads to spatially asymmetric growing space to adjacent trees. The effect of irregular stand structures on tree morphology and growth are investigated in this study, and are based on two stands of Pinus patula (Schiede ex Schltdl. et Cham.) in Langeni Plantation, South Africa. A comparison between trees grown in an all-sided and one-sided spatial competition situation is presented to assess the degree of differences between the two situations. Results of this study show significantly larger crown diameters, crown lengths, longer and thicker branches, disproportionately one-sided crown growth and a reduction in space-use efficiency in stands with irregular competitive status. These factors potentially negatively affect saw timber quality and volume production from the stands at final felling.

Light-lift helicopter logging operations in the Italian Alps: a preliminary study based on GNSS and a video camera system

Bioenergy production from wood is one of the oldest forms of energy and it was for a long time considered a primitive energy source in many industrialised countries. However, it is currently experiencing an increase in attention worldwide. Considering its importance and history, it is astonishing that the widespread cognizance of wood as an important energy source in modern times is a recent phenomenon. It has been mainly driven by the pressure of diminishing fossil fuel resources in industrialised countries, as well as the wish to become more independent from nuclear power and its risks in some developed countries. In addition, amongst other renewable energy sources, bioenergy was identified as an alternative to fossil fuels, which could also help to prevent furthering an anthropogenic climate change by attempting to reduce greenhouse gas emissions. Currently, two different development routes are recognizable, which appear to go in opposite directions and result in competition for land resources in tropical countries. One route is driven by developing countries and the other by developed countries. Globally, wood is the most important source of renewable energy and is used to produce more energy than all other renewable energy sources combined (FAO 2012). According to, the global annual woodfuel consumption, which comprises fuelwood, charcoal and other wood based energy sources, sums up to 1.87 billion m3. Of this amount, 13 % are consumed in the tropical and sub-tropical regions of the Americas and Caribbean region, 30 % in Africa and 30 % in Asia and the Pacific region. In total, almost three quarters of the global woodfuel consumption occur in tropical countries.

Biomass equations for selected drought-tolerant eucalypts in South Africa

Terrain access is a critical factor influencing the feasibility of forest operations in steep mountainous terrain. Long extraction distances coupled with terrain obstacles can favor the use of helicopters in timber extraction in such areas. However, helicopter logging in the Italian Alps is not commonplace when compared to other Alpine regions, for example, in Switzerland and Austria. The use of light-lift helicopters has recently caught the attention of practitioners as an alternative to more traditional medium- to heavy-lift aircraft in the Alps. This article reports the findings of two preliminary case studies using light-lift helicopters for the extraction of high value timber and fire-damaged timber subsequently exposed to bark beetle disturbance. In order to provide a comprehensive analysis of the factors affecting helicopter logging productivity, the two case studies were separately analyzed using time-element analysis supported by on-board global navigation satellite system (GNSS) devices. Additionally, an external video camera was used to continuously monitor the operations. The payload utilization was 86% for the extraction of high value timber and 70% for fire-damaged timber subsequently exposed to bark beetle disturbance. Variation in the turn time was mostly related to the hooking, choker return, and load times, as well as flying distance. Above all, the load hooking time explains c. 27% of the variance, revealing its critical influence on logging productivity.

Cost-productivity analysis of South African pine sawtimber mechanised cut-to-length harvesting

In the water-scarce environment of South Africa, drought-tolerant eucalypt species have the potential to contribute to the timber and biomass resource. Biomass functions are a necessary prerequisite to predict yield and carbon sequestration. In this study preliminary biomass models for Eucalyptus cladocalyx, E. gomphocephala and E. grandis · E. camaldulensis from the dry West Coast of South Africa were developed. The study was based on 33 trees, which were destructively sampled for biomass components (branchwood, stems, bark and foliage). Simultaneous regression equations based on seemingly unrelated regression were fitted to estimate biomass while ensuring additivity. Models were of the classical allometric form, ln(Y) = a+x1ln(dbh)+x2ln(h), of which the best models explained between 70% and 98% of the variation of the predicted biomass quantities. A general model for the pooled data of all species showed a good fit as well as robust model behaviour. The average biomass proportions of the stemwood, bark, branches and foliage were 60%, 6%, 29% and 5%, respectively.

Modelling of wander ratios, travel speeds and productivity of cable and grapple skidders in softwood sawtimber operations in South Africa

The South African forestry industry is experiencing an increase in the number of fully mechanised timber-harvesting systems. Understanding the productivity of these systems, for which data is currently limited for South Africa, is an important step to maximise the utilisation of machines being used. A time study of a mechanised cut-to-length system was conducted in Pinus elliottii sawtimber plantations in the Southern Cape forestry region of South Africa. A harvester and a forwarder were studied with the intention of analysing the division of work time amongst work elements, modelling each machine’s productivity and cost, and estimate fuel consumption. For the harvester’s productivity, a multiple regression model was developed using diameter at breast height (DBH), average distance moved per work cycle and slope class as predictors (adjusted R2  = 0.80). The harvester had a mean productivity of 33.6 m3 per productive machine hour (PMH0) under the current conditions with most of the productive time being used in the moving element. It consumed 25.5 L PMH0 −1 of diesel on average. The forwarder’s fuel consumption was calculated as 16.8 L PMH0 −1, while productivity was 46.8 m3 PMH0 −1. The forwarder spent the longest portion of the work cycle in the loading and unloading phases. A productivity regression model was created that included load size and distance moved during the driving in the loaded phase (adjusted R 2 = 0.78).

On-board computing in forest machinery as a tool to improve skidding operations in South African softwood sawtimber operations

The objective of this study was to develop predictive models for cable and grapple skidder wander ratios, travel speeds (loaded and unloaded), and productivity in softwood roundwood sawtimber harvesting operations. For field data collection, the study utilised on-board computing systems supported by manual time study. Four-hundred and twenty-seven extraction cycles over varying terrain and tree sizes were studied for 13 sites in the Western, Southern and Eastern Cape, and KwaZulu-Natal. Machine make and model as well as gross power rating were studied. Due to insignificance across skidder types and configurations, the objective of creating a predictive model for skidder wander ratio was not met. The overall mean wander ratio for all skidders and terrain studied was 1.12:1. This value was used in the models subsequently developed. No differences were found for unloaded and loaded travel speeds between individual skidder types and speeds were found to be 7.3 km h−1 and 5.5 km h−1, respectively. In terms of productivity, when based on field-measured data, there were differences between skidder types with cable skidders achieving 43.9 m3 per productive machine hour (PMH) and grapples skidders 123.9 m3 PMH−1. The study, however, found that both cable and grapple skidders were only hauling approximately 50% of their capacity and for that reason multiple regression models to predict potential production at full payload capacity were developed for the two skidder configurations. Multiple regression was also used to develop prediction models for travel speeds loaded and unloaded. The study met its objectives for driving speeds and productivity, and the developed models will be used in a subsequent network analysis to provide solutions to optimise the softwood sawtimber supply chain. The study also found that the human element had an impact on the factors studied and that good training, planning, implementation and operational control are imperative to ensure supply (or value) chain goals are met.

Fibre volume losses of eight softwood clearfell harvesting systems in South Africa

On-board computing (OBC) systems in South African timber-harvesting operations are currently limited because of the lack of local expertise and experience. In this study three trials were conducted, monitoring three skidder extraction operations at three sites in South African softwood sawtimber operations. Both cable and grapple skidders were equipped with a MultiDAT data collection device. For all trials, parallel manual time studies were conducted. The results from the time-studies were then used as the basis for evaluation of the accuracy of the information gathered by the OBCs. The results demonstrated the usefulness of OBC devices. This paper reports the results of the application of various tools to support these assessments, considering different levels of complexity, different detail of the results and different fields of application (business uses and research purpose). With regards to the estimation of the machine utilisation rate, it was highlighted that the use of the vibration sensor with additional input from the machine operator in order to define the reason for stopping offered the best solution with an error ranging from -0.74% to +5.54%. This tool can be used in long-term monitoring to identify the possible under-utilisation of a machine and consequently to establish a working system that provides greater productivity. For the evaluation of machine utilisation, the simple analysis of the GPS track-log also provided good results with an error ranging from 4.29% to -4.25%, but it required time-consuming post-operation processing of the raw data in order to correctly interpret. The use of GPS data to perform work studies in general worked reasonably well, the main problem being again that, at certain stages, the process was not easily automated and tended to require time-consuming post-operation data manipulation. However, because of the amount of information derived from data processing, it presents a useful research tool. The introduction of simple OBCs in South Africa is possible, but does require organisational changes and adaptations from both machine operators, who need to be trained to understand and manage the specific user interface and data transmission, and from management responsible for data storage, collation and analysis, and subsequently the implementation of results in improving forest operations.