Productivity and Cost of Mechanized Whole-Tree Harvesting of Fast-Growing Eucalypt Stands

The performance of alternative equipment for the whole-tree harvesting of eucalypt stands was evaluated, using data from five different commercial operations. The study covered three machines for felling and bunching, two for extraction (skidding), and two for combined delimbing, debarking and chipping. Productivity and operating cost models were evaluated for each of the machines, in order to estimate the net harvesting costs under varying forest stand and site conditions. It was found that under easy terrain conditions (flat terrain, dry ground), trees should be felled by three-wheeled feller-bunchers and extracted by front-end loaders, as this combination had the lowest harvesting costs. Due to mobility limitations, this equipment may have to be replaced by tracked feller-bunchers and conventional skidders in steep terrain and/or soft ground. It was estimated that the cost of using the wheeled feller-buncher and the front-end loader system ranged between 16-22$ per oven-dry-ton (odt), depending on tree size. If difficult terrain imposes a shift towards the second, more expensive combination, harvesting cost will increase by about 30% and may exceed 25 $/odt for an average tree weight less than 0.1 odt. Unit costs are inflated by 30% if the hog fuel is considered a by-product and the harvesting cost is charged entirely on the clean chip