Fuel consumption of timber harvesting systems in New Zealand

Abstract

Fuel is a major cost in logging and is also relied on by logging contractors in New Zealand to adjust unit logging rates in dollars per cubic metres ($/m3). There is however, no benchmark on fuel consumption rates in litre per cubic metres (l/m3) in New Zealand, making it difficult to optimise logging operation during planning. A study on fuel consumption of timber harvesting systems in New Zealand was conducted with the participation of 17 ground-based (GB) and 28 cable yarding (CY) logging contractors with crews working commonly on pine plantations (Pinus radiata). The logging contractors, distributed in both the North and the South Islands of New Zealand, provided data on fuel use, production, stand and terrain attributes, type and number of machines used by month or year of harvesting. This data was used to determine and set benchmark on rates of fuel use in l/m3 and litres per kilowatt-hour (l/kWhr), and establish the proportion of unit fuel consumption costs in unit harvesting costs by type of harvesting system. All the GB systems combined harvested approximately 1.1 million cubic meters of timber using 2.94 million litres of fuel. Similarly, all the 28 CY systems combined harvested approximately 1.5 million cubic metres by consuming 4.6 million litres of fuel. Results showed that on average, the rates of fuel use for GB systems combined was 3.04 l/m3 and 0.15 l/kWhr, while that of CY systems was 3.18 l/m3 and 0.09 l/kWhr. There was no clear difference in average rates of fuel use in l/m3 between GB and CY unlike rates of use in l/kWhr. Using comparable data from GB systems in the Southern US states of Alabama, Georgia, Florida, Louisiana, and North Carolina, on average, GB systems in New Zealand use 32% more fuel per unit of production. Sensitivity analyses based on unit harvesting rates ($/m3) from harvesting benchmarking data and average fuel (diesel) prices for 2013 in New Zealand showed that fuel costs per unit volume of wood harvested, on average, constitutes 16 and 14% for GB and CY operations, respectively per unit cost of harvesting. The study concluded that on average, GB and CY harvesting systems use the same rates of fuel use in l/m3. The rates of fuel use in l/m3 were found to be dependent on total production, slope of harvesting sites and directions of pulling during extraction. The results of the study also showed that GB and CY harvesting systems use different rates of fuel in l/kWhr. The rates of fuel use in l/kWhr were found to be dependent on the type of harvesting system used, total production, number of machines used, average power, slope, directions of pulling during extraction and surface moisture conditions during harvesting. The results of this study will contribute significantly to the understanding of logging fuel use by providing a benchmark on rates of use in l/m3 and l/kWhr, for harvesting planning, adjustment of logging rates, and updating the existing machine costing spreadsheet. The rates of fuel use in l/m3 reported in this study will also be applicable in comparing operational costs between harvesting systems and machines for purposes of economic efficiency.