• Energy Research

Abstract 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%.

The study used time studies and cost analysis to assess potential economic benefits from site preparation cost reductions resulting from producing coarse woody harvesting residue (CWHR) for bioenergy. In contrast, previous studies have predominantly used anecdotal estimates of site preparation costs.The study was performed in a recently clearfelled 15-year-old plantation of Eucalyptus globulus (Labill) in Tasmania, Australia. The study area consisted of the control area (0.51 ha), containing ~35 m3 ha-1 of CWHR and the CWHR harvest area (2.47 ha), containing &le;12 m3 ha-1 of CWHR. The control area had been harvested with a harvester &ndash; forwarder system, which left all harvesting residue (HR) onsite, where-as the CWHR harvest area had been harvested with a feller-buncher &ndash; skidder &ndash; processor system which removed most of the HR. The latter site was used to simulate an area where CWHR had been harvested. The study examined productivities and costs of machines performing site preparation in each area. The preparation of the control area site was performed with an excavator that windrowed CWHR, fol-lowed by a skidder-mounted plough constructing planting furrows. Residual CWHR post-windrowing was <1 m3 ha-1. Productivities and costs were 0.53 ha PMH0-1 and AUD$319 ha-1 for the excavator and 1.1 ha PMH0-1 and AUD$139 PMH0-1 for the skidder-mounted plough. The excavator was not required in the CWHR harvest area. In this area, skidder-mounted plough productivity and cost were 1.16 ha PMH0-1 and AUD$109 ha-1 suggesting CWHR reduction to &le;12 m3 ha-1 could reduce site preparation costs by AUD$319 ha-1. Further studies on costs and revenues associated with CWHR removal and sale are required to determine net economic benefits and determine excavator cost and productivity for a range of CWHR quantities.

Abstract 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.

Background: Forest biomass is a major global source of biofuel. To compete with other energy sources its delivered costs need to be reduced. Globally, logging residue (LR) is likely to be the cheapest, readily available forest biomass form. LR transport is a major cost component. Methods: A harvester-forwarder harvest system was studied in two adjacent areas to compare Swedish “fuel-adapted harvesting” with conventional cut-to-length harvesting at the stump in a mature Pinus radiata D.Don plantation in Western Australia to assess the impact of fuel-adapted harvesting on costs and productivity of a harvester and forwarder producing logs and extracting LR and on LR yield. Results: Harvester and forwarder productivities producing logs were significantly reduced in the fuel-adapted area compared with the conventional area which increased log production costs for the fuel-adapted site by 15%. Forwarder productivity extracting LR and LR yield were significantly greater in the fuel-adapted area which reduced LR extraction costs by approximately 28%. This was due to the ease of loading LR from residue piles created during fuel-adapted harvesting compared with loading scattered residue from conventional harvesting. The cost reduction for LR extraction from the fuel-adapted area exceeded the increased log harvest and extraction costs. This resulted in the combined log and LR costs for the fuel-adapted area being approximately 12% lower than those for the conventional area. Increased forwarder productivity through adoption of larger load bunks and residue-specific grapples combined with increased operator experience with fuel-adapted harvesting would be likely to further decrease log and LR production costs. Conclusions: The results show that adoption of fuel-adapted harvesting could reduce LR delivered costs, thus increasing its viability as a biofuel. However, primary transport cost is only one component of LR delivered costs and needs to be considered in combination with the reduction of other supply chain costs, particularly secondary transport costs which can make up a large proportion of LR delivered costs. Because removal of most LR from a site can reduce subsequent tree growth, guidelines specifying the proportion of LR retained should be considered.

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.

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 productivity (65 m3 PMH0−1) was less than expected as it appeared to be underpowered to handle the larger trees on the study site. The skidder’s productivity (56 m3 PMH0−1) was comparable to those reported in studies under similar conditions and with bark retained. The roadside processor’s productivity (25 m3 PMH0−1) was lower than expected.This was believed to result from the operator separately stacking 10 m and 5 m logs, and the lower feed speed resulting from slippage due to the reduced feed roller pressure used in the study to reduce bark loss. Future research could identify feed rollers that increase feed speed while retaining bark. Harvest system costs (AUD18 GMt−1) were similar to those reported for a eucalypt roadside processing trial where bark was removed. These results suggest that retaining bark on the logs at roadside did not affect the harvesting system’s productivity or costs.Keywords: Whole tree to roadside, harvest system, bark, bioenergy, biomass, Eucalyptus nitens, Australia

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 <20 mm during the first week of the scheduled period did not significantly effect delivered costs.

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...