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Drying forest biomass at roadside can reduce transport costs and greenhouse gas emissions by reducing its weight and increasing its net calorific value. Drying models are required for forest supply chain analysis to determine optimum storage times considering storage costs and returns. The study purpose was to evaluate the impact of the source of meteorological data on the goodness of fit and practical application of Eucalyptus nitens log pile drying models. The study was conducted in Long Reach, NE Tasmania, Australia from the 6th of February to 6th of August 2020. Four data sources were compared: the nearest meteorological station, interpolated meteorological data, a portable weather station, and digital temperature/RH sensors. Predicted moisture content (MC) values from the only previously published E. nitens log pile drying model were also evaluated using the current study data sources as inputs.Log pile MC changes were determined from weight changes measured by placing the study logs on a steel frame bolted to load cells at each corner. As the study was based on debarked logs, dry matter losses were assumed to be negligible. Initial MC of the logs was determined by extracting samples using an electric drill and drying them until constant weight was achieved.Initial log pile drying rates were high with several daily MC losses >2%. Portable weather station data produced the best goodness of fit drying model. The second-best goodness of fit model was based on meteorological station data. From a user acceptability perspective (highest proportion of results within ±5% of measured values), the best model was based on temperature/RH sensor data. Goodness of fit measures for the temperature/RH sensor data model were poorer than for the other data sources, but still acceptable. The published E. nitens log drying model had the poorest results for goodness of fit and user acceptability.In conclusion, portable weather stations are best suited to research trials due to the expense of placing a weather station at each log pile. Drying models based on data from the nearest meteorological station or temperature/RH sensors are best suited for practical applications, such as forest supply chain analysis. Additional benefits could accrue from a forest estate-wide network of low cost temperature/RH sensors potentially supplying data to forest supply chain analysis as well as fire prediction and tree growth models.

Forest biomass (FB) could supply more of Australia’s energy needs, but delivered costs must be reduced for it to be a viable energy source. Operational planning is critical to reducing delivered costs as it determines actual activities, though few operational FB supply chain (FBSC) planning tools have been published. This paper presents a “proof-of-concept” operational FBSC decision support system (DSS) to schedule FB deliveries for eight weeks from roadside storage for the least cost, taking in account moisture content changes. Four mathematical models are compared, solving a linear formulation of the FB delivery problem in terms of solution speed and delivered cost, and the practicality of implementing the solutions. The best performing model was a Greedy algorithm as it produced solutions not significantly different from those of the tested linear programming solver and was readily modified to significantly improve solution implementation through the addition of a non-linear element. FBSC planning tools typically assume accurate knowledge of stored FB quantities and that little or no rainfall occurs during storage. In practice, stored FB quantity estimates can be inaccurate due to variation in the bulk density of the piles. Improving these estimates is a critical area for future research. This study found that simulated rainfall with

Australia’s large potential forest bioenergy resource is considerably underutilised, due largely to its high delivered costs. Drying forest biomass at the roadside can potentially reduce its delivered cost through weight reduction and increased net calorific value. There has been little research on the impact of roadside drying for Australian conditions and plantation species. This study compared delivered costs for three forest biomass types—Eucalyptus globulus plantation whole trees and logging residue (LR)-disaggregated (LR conventional) or aggregated (LR fuel-adapted)—and three roadside storage scenarios—no storage, ≤two-month storage and optimal storage—to supply a hypothetical thermal power plant in south-west Western Australia. The study was performed using a tactical linear programming tool (MCPlan). Roadside storage reduced delivered costs, with optimal storage (storage for up to 14 months) producing the lowest costs. Delivered costs were inversely related to forest biomass spatial density due to transport cost reductions. Whole trees, which had the highest spatial density, stored under the optimal storage scenario had the lowest delivered costs (AUD 7.89/MWh) while LR conventional, with the lowest spatial density, had the highest delivered costs when delivered without storage (AUD 15.51/MWh). For both LR types, two-month storage achieved ~60% of the savings from the optimal storage scenario but only 23% of the savings for whole trees. The findings suggested that roadside drying and high forest biomass spatial density are critical to reducing forest biomass delivered costs.

Forest biomass (FB) is widely used overseas as an industrial energy source, particularly in Europe, but is currently little used in Australia. Typical attributes of FB disadvantage it as a fuel rel...

With their widespread utilization, cut-to-length harvesters have become a major source of “big data” for forest management as they constantly capture, and provide a daily flow of, information on log production and assortment over large operational areas. Harvester data afford the calculation of the total log length between the stump and the last cut but not the total height of trees. They also contain the length and end diameters of individual logs but not always the diameter at breast height overbark (DBHOB) of harvested stems largely because of time lapse, operating and processing issues and other system deficiencies. Even when DBHOB is extracted from harvester data, errors and/or bias of the machine measurements due to the variation in the stump height of harvested stems from that specified for the harvester head prior to harvesting and diameter measurement errors may need to be corrected. This study developed (1) a system of equations for estimating DBHOB of trees from diameter overbark (DOB) measured by a harvester head at any height up to 3 m above ground level and (2) an equation to predict the total height of harvested stems in P. radiata plantations from harvester data. To generate the data required for this purpose, cut-to-length simulations of more than 3000 trees with detailed taper measurements were carried out in the computer using the cutting patterns extracted from the harvester data and stump height survey data from clearfall operations. The equation predicted total tree height from DBHOB, total log length and the small end diameter of the top log. Prediction accuracy for total tree height was evaluated both globally over the entire data space and locally within partitioned subspaces through benchmarking statistics. These statistics were better than that of the conventional height-diameter equations for P. radiata found in the literature, even when they incorporated stand age and the average height and diameter of dominant trees in the stand as predictors. So this equation when used with harvester data would outperform the conventional equations in tree height prediction. Tree and stand reconstructions of the harvested forest is the necessary first step to provide the essential link of harvester data to conventional inventory, remote sensing imagery and LiDAR data. The equations developed in this study will provide such a linkage for the most effective combined use of harvester data in predicting the attributes of individual trees, stands and forests, and product recovery for the management and planning of P. radiata plantations in New South Wales, Australia.

Few studies have considered potential climate change impacts on forest operations. A review of the literature found that predicted changes to Australian forest growth and mortality varied between regions depending on the models and assumptions used. Impacts of climate change on forest operations will depend on the magnitude and speed of the climate changes and the management decisions used to adapt to these changes. If forest growth declines and management changes are not able to maintain current mean tree sizes at final harvest, costs and productivity of forest harvest and haulage operations at an individual harvest unit level will be affected. Slower forest growth would also mean that less harvest and haulage capacity would be required, unless additional forest planting occurs.The literature review identified the potential for substantial areas of the Australian Eucalyptus globulus plantation estate to be less productive in the second rotation due to the impacts of climate change on growth and t...

Time consumption and productivity of a Valmet 890.3 8 wheel forwarder were evaluated on an Australian radiata pine clearfell site with a slope of 21 to 45% (12 to 24°). Cycle time was significantly related to extraction distance. Productivity was significantly related to extraction distance and load volume. Slope did not have a significant effect on cycle time or productivity. Productivity was considerably greater than that for many published studies, which was likely to have been the result of many factors at the study site affecting load sizes and cycle times, including the large load capacity of the studied forwarder, larger mean log volumes, larger log volumes per loading stop, fewer log assortments, potentially larger forwarder grapple volume capacity, log lengths suited to efficient loading and higher travel speeds.;

Coppice regeneration of eucalypt plantations is increasingly being used in Australia to reduce re-establishment costs. However, little is known about the impact of early coppice reduction regimes on harvester performance during clearfelling. The trial compared the productivity, time consumption, cost and fuel use of a single-grip harvester (Hyundai 210LC-9 base and SP 591LX harvesting head) clearfelling a 10.5-year-old, second-rotation coppiced Eucalyptus globulus stand in south-west Western Australia for chip logs. Coppice stems had been reduced to one stem or two stems per stool or left untreated. Time and piece counts were used to determine harvester productivity. Harvester cycle and elemental times and the number of logs and harvester head passes per stem were obtained from video recordings. Harvester fuel use was determined by refilling the fuel tank to the same point each day. Stem size was the major factor influencing harvester productivity (20.8 m3 per productive machine hour without delays [PMH0]...

Forest biofuel delivered costs are generally uncompetitive with fossil fuels. Drying forest biofuel can potentially reduce delivered costs through weight reductions and net calorific value increases. The study examined the impact of roadside drying (RD) and use of high-volumetric capacity trucks on delivered costs of Pinus radiata pulp-logs and logging residue (LR) chips supplying a gasification plant. Five truck configurations: 6-axle semi-trailers; 9-axle B-doubles; proposed high-volumetric (HV) capacity versions of these trucks (HV semi-trailers and B-doubles); and 11-axle pocket road trains (PRT), were investigated across six supply areas using a forest biomass supply chain tool. Without RD all truck configurations were weight limited transporting logs, and all (except HV semi-trailers and B-doubles) were volume limited transporting LR chips. Post-RD all truck configurations were volume limited transporting logs or LR chips, (except HV B-doubles transporting logs). RD considerably reduced delivered costs: PRT (22%), B-doubles (24%), semi-trailers (25%) for logs and PRT (28%), B-doubles (29%), semi-trailers (30%) for LR chips. Delivered cost differences between truck configurations reflected transport cost differences. Without RD, truck trips transporting log were directly related to truck weight capacity. Additional volumetric capacity enabled HV semi-trailers and B-doubles to transport 6% and 4% more LR chips than standard versions, respectively, with equivalent truck trip reductions. RD weight reductions were: logs (33%); LR chips (53%), with consequent reductions in truck trips. PRTs required fewest truck trips to transport logs and LR chips without RD and the second fewest for logs post-RD due to their high weight and volumetric capacities.

Australia’s eucalypt plantation estate (>900 000 ha) has largely been established since 1995. The main species is Eucalyptus globulus producing wood chips for export on a short rotation (~1...

There is increasing interest worldwide in using tree harvesting biomass as an energy source. Bark retained on logs is commonly used as an energy source, but is generally removed from eucalypt logs during harvest. In order to evaluate the potential use of eucalypt bark as fuel, there is a need for information on the productivity and cost implications of retaining eucalypt bark during harvest operations. The study examined the impact of retaining bark on logs on the productivity and costs of a whole‑tree to roadside harvesting system in a short‑rotation Eucalyptus nitens plantation in Australia being harvested for pulp logs. Trees were felled and bunched with a feller‑buncher in spring, then left infield for four weeks to promote bark adhesion and reduce bark loss. A skidder extracted the trees to roadside where a processor processed them to predominantly 10 m logs. Machine productivities were calculated from estimated tree and log volumes and cycle times recorded from video recordings. The feller‑buncher's...

Manual time and motion studies are the most common method to collect forest harvesting machine performance data. However, manual methods require skilled observers and are generally limited in duration, making it difficult to obtain a sufficiently large sample for machines with long cycle times such as skidders and forwarders. Of the automated data capture techniques studied previously, few have the breadth and ease of application to conduct long term autonomous studies for a range of harvesting machines. Analysis of Global Positioning System (GPS) data has been successfully trialled previously to conduct time studies of comparable accuracy with skilled observers, however, these approaches have been limited by the need for a degree of manual data processing. The current study trialled a fully automated system using analysis of GPS and vibration sensor data to estimate cycle times and time elements, and compare them with those determined using traditional time and motion studies for three forwarders at different sites. The mean difference between the cycle times estimated by the two methods was

The impact of the manipulation of plantation stocking density on individual tree size can affect final harvest costs and machine productivity. This paper investigated the impact of four early-age thinning treatments applied to a Eucalyptus globulus Labill. pulplog plantation in south-west Western Australia on economic profitability and harvester productivity. Eighteen sample plots were randomly laid out in the study area. The nominal 700, 500, and 400 stems per hectare (sph) plots were thinned to waste 3.2 years after establishment while the nominal 1000 sph (UTH) plots were left unthinned. The economic analysis showed that all thinning treatments resulted in a lower Land Expectation Value (LEV) and net financial loss over the full rotation at their theoretical optimal rotation age when compared with the unthinned control treatment. Tree growth and form were positively impacted by thinning. However, associated reductions in harvesting costs were less than the value losses resulting from reduced per hectare yield.

Reductions in Pinus radiata D. Don. (radiata pine) clearfell age have increased the juvenile wood proportion in sawlogs, increasing the need to segregate low modulus of elasticity (MOE) material early in the supply chain to avoid the costly processing of low-value, non-structural boards. In Australian radiata pine plantations, variability in MOE is greater between trees than between stands, requiring tests of individual trees to identify those with low MOE. Time of flight of a sound wave in a tree or log is known to be well-correlated to its MOE. The trial examined the ability of a newly developed acoustic assessment tool, the Hitman PH330 (PH330) supplied by Fibre-gen Limited, fitted to a harvester head, to identify and segregate low MOE sawlogs during a cut-to-length harvesting operation in a radiata pine plantation. The impact of using the tool on the harvester’s productivity was also examined. There was a reduction in the mean productivity of the harvester when using the PH330 compared with normal ope...

Significant quantities of woody biomass from the tops of trees and larger woody ‘waste’ pieces that fall outside existing sawlog and pulpwood specifications are left on site post final harvest in Australian radiata Pinus radiata (D. Don) (radiata pine) plantations. Woody biomass is a potential product for pulp making or energy generation. Commercial use of woody biomass from radiata pine plantations would add extra value to the Australian plantation estate through improved resource utilisation, and potentially reduced post-harvesting silvicultural costs. This study investigated the productivity and cost impact of the harvest and extraction to roadside of woody biomass in an integrated harvest operation in a typical Australian two machine (harvester/processor and forwarder), cut-to-length, clearfall operation in a mature, thinned radiata pine plantation. The harvest operation yielded 23 GMt/ha (5% of the total yield) of woody biomass (known as ‘fibreplus’), 443 GMt/ha of sawlogs and 28 GMt/ha of pulpwood. The mean quantity of biomass left on site was 128 GMt/ha, mainly consisting of branches and needles, sufficient to minimise nutrient loss and protect the soil from erosion. Woodchips derived from the fibreplus product were suitable for kraft pulp making, (when blended in small amounts with clean de-barked roundwood woodchips), and for energy generation. The method trialed with the fibreplus product being produced did not impact harvesting and processing productivity and costs, but extraction was 14% less productive. Through analysis of the productivities of each phase and development of a cost model the harvest and extraction of the fibreplus product was estimated to increase total unit costs by ∼4.9%.

Productivity of a mechanized harvesting system is influenced by stand and terrain conditions, operator performance, and machinery limitations or design. The purpose of the study was to compare the productivity of two near-identical single-grip harvesters in similar Australian Pinus radiata clearfell harvesting operations on a log-by-log basis. The study first compared the productivity of each harvester against tree volume for cycle times and for tree processing times only. Significant differences in productivity between the harvesters were found to be largely due to significant differences in tree processing times. Comparisons between each component of processing time (dragging-out time, disc-cutting time, cross-cutting time, harvester head travel time and delimbing time) for a subset of 6.1 m sawlogs at each study site found operator working technique differences to be the main driver of productivity differences between the harvesters. In particular, the operator of the less productive harvester dragged ...

Productivity models produced using time differences between consecutive StanForD stem files collected by harvester onboard computers were compared with models produced using traditional time and motion techniques for the same initial trees. Three sites were studied in Pinus radiata plantation clearfell operations across southern Australia. Delays and trees with multiple leaders or broken tops were removed from the data. This was done for the stem file data using filters. The same filters were applied to data from all sites. No significant differences were found between the models at each site, though the stem file productivity models generally had a poorer fit than the time and motion models. The advantages of using stem files for modelling are the ready availability of stem file data, which enables rapid creation of generalised harvester productivity models and avoids short-term changes in productivity caused by the presence of an observer (the “Hawthorne effect”). Disadvantages are the inabilit...

Mechanised harvesting operations are popular in Australia because of their productivity and efficiency, improved worker safety and reduced cost of operations. Most research has found that the productivity and efficiency of a mechanised harvesting system is affected by a number of factors such as forest stand characteristics, terrain variables, operator skill and machinery limitations. However, current studies did not quantify these factors sufficiently to evaluate the productivity and efficiency effects that can guide allocation of different harvesting equipment. This article reviews the literature on how major forest stand characteristics such as tree size and undergrowth affect the productivity and efficiency of a harvesting machine and/or system in clearfelling operations, and explores the application of remote sensing technology including multi-spectral imagery and LiDAR (light detection and ranging) to identify and quantify these characteristics to allow for better harvest planning and harvest system allocation. It is concluded that by evaluating the interactions between each of these factors and different types of harvesting equipment, an empirical model could be developed to optimise the use of current harvesting systems and assist the selection of more cost-effective harvesting machinery, using remote sensing.

Harvesters estimate bark thickness primarily from diameter over bark (DOB) and use it to estimate log volume and value. Harvester bark thickness estimation errors can reduce returns through poor bucking optimisation and out-of-specification logs. Radiata pine bark thickness data from harvested logs and permanent sample plots (PSP) were analysed to determine best-fit coefficients for current and potential future harvester bark thickness models. The most suitable current harvester bark thickness model for radiata pine is: double bark thickness = b 0 + b 1*DOB (the ‘DOB model’). This describes a straight line, whereas radiata pine bark relative to DOB is thicker near the stem base and consistent over the remainder. PSP data set coefficients for this model overestimated upper stem bark thickness and underestimated lower stem values. The harvester model for Scots pine bark fitted better than the DOB model for diameters

Previous studies of harvester measurement accuracy assumed traditional manual log measurements were accurate and represented true log dimensions, which relies heavily on the assumption that logs are regular in shape. The objective of this study was to quantify the level of variability in manual log measurements and consider its impact on harvester calibration and accuracy assessments. Log length was measured along the top and each side and small-end diameter with callipers, a diameter tape, and a steel ruler in two radiata pine stands near Mt. Gambier in Southern Australia. Observed variability in manual log measurements was sufficient to affect harvester accuracy studies and calibration. Length variability on different sides of a log occurs mainly from non-square log ends. Differences due to observer were minor. Diameter measurement variability occurs mainly from the effect of stem eccentricity on each instrument, which is dependent on its number of stem contact points. Callipers have fewer cont...

Slope is a major factor affecting forest harvesting machine productivity. As ground-based harvesting methods are generally cheaper than the alternatives, forest managers need to know when ground-based harvesting equipment can be used on sloping sites. The study objective was to determine the effect of slope on the productivity, cycle time and elemental times of a Valmet 450 FXL self-levelling processor processing a 24 year-old, unthinned radiata pine plantation previously felled and stacked by a feller-buncher. The study site slope was estimated using a LiDAR (Light Detection and Ranging) derived digital terrain model and classified using the regional terrain classification system. Study trees were selected from areas predominantly in the hilly (12–19°) and steep (20–26°) slope classes, as these classes made up the majority of the study site area. In contrast to previous research, no significant differences were found between the processor productivity, cycle time and elemental times (moving/positioning, swinging and processing) between the slope classes. This was believed to result from the processor working well within its capabilities processing the relatively small trees on the study site. Other important factors may have included that the trees were pre-felled by a feller-buncher and placed in high density rows with their butt ends aligned, which minimised the processor boom and track movements, and that steep slope trees were selected from areas at the lower end of the steep slope class (20–23°). Further research is needed to determine whether the processor productivity would be significantly lower when processing larger trees on steeper slopes.