Harvesting forest biomass in the US southern Rocky Mountains: cost and production rates of five ground-based forest operations

The forests of the southern Rocky Mountains of North America have experienced substantial change since European colonization. High-grade logging, forest grazing practices, and fire suppression have altered once park-like ponderosa pine-dominated ecosystems into dense forests in need of restoration treatments, but such treatments are challenged by the low-value wood products removed during treatment. This study aims to understand and evaluate restoration harvest practices in the southern Rocky Mountains in terms of equipment used, production rates, and costs under both observed and modeled site and stand conditions across the region. During the summer of 2017 we observed five ground-based harvest operations of varying size and capacity across the region and analyzed their characteristics using detailed time study data. Observed stump-to-truck harvest rates ranged from $19.11 to $43.25 United States Dollars per tonne with an average of $29.70 per tonne, and modeled costs based on standardized variables from $19.95 to $33.39 per tonne with an average of $26.19 per tonne. Observed average productivity rates for felling, skidding, processing, loading, and biomass grinding were respectively 22.9, 16.0, 20.7, 27.8 and 49.8 tonnes per scheduled machine hour (SMH). Under modeled conditions for the same functions except grinding, productivity averaged 25.4, 18.6, 23.1, and 28.2 tonnes per SMH. Results from this study will be used as a benchmark for efficiency and costs and to model region-wide biomass production.