Economic impact of truck-machine interference in forest biomass recovery operations on steep terrain

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Date: May-June 2013
From: Forest Products Journal(Vol. 63, Issue 5-6)
Publisher: Forest Products Society
Document Type: Abstract
Length: 7,645 words
Lexile Measure: 1390L

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Abstract

In forest biomass recovery operations from harvest residues, processing equipment can work most productively if they can work without interference or waiting on trucks. A deterministic simulation model was developed to estimate the economic effect of truck--grinder interference in forest biomass processing and transport operations on steep terrain. Truck-machine interference can occur in situations where the grinder is waiting for trucks or vice versa. We analyzed how the number of available trucks and road characteristics affect grinder utilization and biomass delivery cost. Three cases based on different road characteristics were designed and applied to actual operations in order to illustrate how particular road features in relation to the spatial location of the grinder can affect the economics of the operation. An economic model was also developed to estimate the waiting cost of trucks and machinery due to truck--machine interferences. Grinder location in relation to available truck turnaround, turnouts, truck turning-around time, truck positioning time, and distance traveled on each road surface have a significant effect in forest residues processing and transport economics at the operational level. After the optimization was performed, the grinder utilization rate on a harvest unit with highly constrained road access reached 60 percent using six trucks. Waiting cost represented 15.15 percent of total grinding cost. On the medium constrained road access harvest unit, maximum grinder utilization reached 77 percent using five trucks. A loop road case resulted in a grinder utilization rate of 81 percent using five trucks.

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A growing market for forest biomass from logging residues is being developed due to the increasing interest in developing renewable sources of energy as replacements for liquid fuels and electricity. Logging residues are one of the few available renewable sources of material with few competing uses. Currently, logging residues are often piled and burned to assist in reforestation. The amount of available residues is a function of the physical characteristics of the species, forest composition, type of logging operation (cable logging or ground-based equipment), and timber-pulp market requirements (Hakkila 1989). The US Department of Energy (2011) estimates that approximately 40 million metric tonnes of forest residues is available following timber harvesting each year in the United States.

Forest residues in the US Pacific Northwest (PNW) are typically comminuted during field operations following timber harvesting using grinders at roadside. Grinders reduce the particle size of the residues (limbs, tops, and other byproducts) by hammering the material with a cutting rotor (Staudhammer et al. 2011). Grinders are expensive machines with engines producing between 500 and 1,000 horsepower that result in high purchase and running costs. Track-mounted grinders have limited mobility to facilitate the placement of the machinery at a processing site. Road accessibility and low driving speeds of the tracked carrier limit machine mobilization within a forest unit. Chippers are also available to process the material. The choice of chipping versus grinding depends on operating conditions and product end use. The ability to operate in the presence of contamination (dirt and rocks), and the high throughput when product specifications...

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Gale Document Number: GALE|A355246526