Compilation of State-of-the-Art Mechanization Technologies for Short-Rotation Woody Crop Production

SUMMARY This report reviews the current state of mechanization of operations, from establishment through harvesting and transportation, for short-rotation hardwood plantations. Given that essentially all of the high production plantations in the U.S. are intended for pulp production, with residues for energy as a secondary product, the report focuses mainly on approaches for producing trees greater than 3 inches DBH (diameter at breast height), although technologies for smaller trees intended solely for energy are also reviewed. Possibilities for improvement are also discussed. Planting of more widely-spaced plantations for pulp is generally still done by hand. For closer-spaced energy plantations, mechanical planters are used. Agricultural seedling transplanters have been successful, and machines intended specifically for planting hardwood cuttings have recently been developed in Scandinavia. Cultural operations-fertilization, weed control and pest control-are carried out with traditional agricultural equipment, ranging from backpack sprayers to small all-terrain vehicles, agricultural tractors and implements, to aircraft. Given the amount of effort that has gone into developing equipment for a wide variety of agricultural operations, and the similarities between establishment and cultural operations for SRWC and other agriculture, improvements in these operations are more likely to be incremental than substantial. To date, conventional forestry equipment and methods have been employed for all operational harvesting, processing and transportation of SRWC in the U.S. for pulp production. These operations are highly mechanized with the most common utilizing feller/bunchers, grapple skidders, a chain flail delimber/debarker/chipper and chip vans. Another replaces the flail/chipper and vans with irongate delimbers, log trucks and a drum debarker. All deliver clean chips to pulp mills. Residues from the flail/chipper or drum debarker may be comminuted with a tub grinder or hammer hog and transferred to an energy production facility by van or conveyer. Conventional forestry equipment is probably not optimal for SRWC plantations; it is used by default because it is productive and reliable. The amount of SRWC harvested has not justified the full-cycle development of specialized equipment for larger trees, i.e., greater than 3 " DBH. But the conditions in SRWC plantations-flat, obstacle-free ground, small trees of uniform size growing in straight rows, uniform road spacing (in many cases), short transportation distances to the mill (in some cases), small branches and bark characteristics which differ from those of conifers-all suggest that SRWC harvesting, processing and transportation can be carried out in different and cheaper ways. Equipment manufacturers and researchers have pursued numerous alternatives for …