The use of roll-off bins and a hook-lift equipped harwarder and truck for forest biomass utilization

Extracting slash for utilization has long been a challenge for forest managers. Issues of accessibility and costs generally prevent biomass utilization. The traditional slash treatment is to pile and subsequently burn slash when environmental conditions allow. A harvesting system consisting of roll-off containers and bunks and a hydraulic hook-lift equipped forwarder combi-machine (or “harwarder”) and haul truck were tested for forest biomass utilization and roundwood harvesting. Detailed time-and-motion studies were conducted at two study sites in Western Montana. The data from these studies were used to develop productive total cycle time equations for processes involved with harvesting and transporting merchantable timber and woody biomass. For each process studied, a statistical model quantifying the total cycle time was developed. Harwarder, cut-to-length, and ground based whole-tree harvest systems were analyzed using productive total cycle time equations and independent variables. Some systems were observed in the field while others were modeled. Sixteen systems (equipment combinations) were analyzed plus one hand slashing system. Systems varied by pre-treatment hand-felling, machine type, and slash treatment. Inputs such as forwarding distance, forest stand conditions, haul distance, and market price were kept constant for the analysis. Roll-off technology can be competitive with traditional slash management options. The most cost effective system incorporated a sawyer for trees less than 4.5 inches DBH, fellerbuncher for roundwood material, rubber-tired grapple skidder, delimber at the landing, and a forwarder for collecting trees less than 4.5 inches DBH. This system resulted in a net cost of $366.59 per acre or $10.77 per ton. System costs ranged from the most expensive being harwarder systems to the least expensive being ground based whole-tree systems. Adding a sawyer to any system to fall trees less than 4.5 inches DBH reduced net costs. Similarly, using a two pass system where felling and processing was completed on the first pass and forwarding was completed on a second pass reduced net costs if hand-felling was also used. Dedicated machine systems resulted in lower costs