A Short Review of Fuel Consumption Rates of Whole Tree and Cut-To-Length Timber Harvesting Methods

The fuel consumption of equipment during forest harvesting operations is still not well known and existing measurement technologies are largely untested. Considering forest industry’s need, some countries have developed and compared tools to quantify, control and analyses fuel consumption to create suitable analysis methods. Comprehensive trials have been carried out by researchers in different countries to quantify the fuel consumption rates for different harvesting methods. This article provides a short review of fuel consumption rates of whole tree and cut-to-length harvesting methods. The article explains the factors influencing the fuel consumption and provides suggestions to control and reduce fuel consumption of harvesting machines.


Introduction
The fuel consumption of equipment during forest harvesting operations is still not well known and existing measurement technologies are largely untested. Considering forest industry's need, some countries have developed and compared tools to quantify, control and analyse fuel consumption to create suitable analysis methods. Despite environmental and economic concerns on the fuel consumption of various harvesting machines due to emissions and increasing fuel costs, there are not many studies available on this topic. This short review article aimed to collect the relevant information through reviewing previous studies in different countries.

Fuel Consumption Rates
Comprehensive trials have been carried out to quantify the fuel consumption rates for different harvesting methods [1]. The cut-to-length (CTL) method, with a harvester and forwarder, used 2.0 L/m 3 which is lower than 2.7 L/m 3 for the whole tree (WT) method, including a feller-buncher, skidder and processor. The CTL systems studied in Austria and Western Australia also had lower fuel consumption per unit volume harvested (Table 1). This might be a result of using two machines within the CTL method compared with three machines in the WT method. The WT operations in the Austrian study, using cable yarder, consumed less fuel per cubic meter of wood harvested than the Canadian and Western Australian case studies. These differences are most likely due to the Austrian case study having a chain saw for felling and a tower yarder for extraction that had very high productivity (Table 1). WT methods using skidders will be more common in areas with difficult terrain with steeper slopes and smaller tree sizes resulting in reduce machine productivity and typically increased fuel consumption per unit volume harvested. Transportation is the most fuel consuming element of a wood supply chain. In Sweden, secondary timber transport consumed about 50% of total fuel usage while harvesting and extraction operations consumed 33-40% [2,3]

Controlling and Reducing Fuel Consumption Rates
Different approaches can be applied to control and reduce fuel consumption in forest operations. FP Innovations in Canada have produced a guide that has also been adapted by Tigercat [5,6]. A few of the key suggestions from guide that may apply for any forest operation include: A.
Use diesel engines at their maximum torque to utilize all potential. Other ideas have been suggested by Finnish scientists to reduce fuel consumption and emissions of ground-based logging systems [7]. These ideas are equally applicable in Australian forest operations; H. Improve driver education, to educate drivers about driving techniques to reduce fuel consumption and to improve driver safety.
I. Switch to another transportation mode, e.g., rail if it is a viable service.

J.
Use the most appropriate size of equipment for the task.
K. Integrate operations (e.g. integrating biomass/residue collection with industrial wood recovery by forwarders in pine plantations in New South Wales and south west Western Australia [8,9]. L.
Use alternate fuels e.g., biofuels derived from forest biomass.
In a German case study, harvesters, forwarders and skidders were classified into small, medium and large classes based on their engine power. Fuel consumption was found to be lower for smaller engine powers which can be taken into consideration as one of the criteria to choose optimum machine size/type [10]. Increased truck payloads have also been shown to reduce fuel consumption per m 3 of wood delivered by over 20% [11,12].

Conclusion
Fuel consumption is impacted by machine design thus choosing appropriate machine size for each task is a key decision. Skilled and educated operators can play a key role to reduce machine fuel usage. A few studies have been recently conducted but more comprehensive trials will be required in harvesting operations to effectively explore how to better manage and reduce fuel consumption within the forestry supply chain.