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Harvest of short rotation woody crops with small to medium size forage harvesters

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  131620174,  2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: 10.13031/aim.20131620174) @2013
Authors:   Philippe Savoie, Pierre Luc Hébert, François-Simon Robert
Keywords:   willow woody crop harvest chopped pull-type medium-size

Abstract. Willow and poplar plantations for short rotation woody crops (SRWC) were originally developed to provide bioenergy and forestry biomass on a large scale. As a consequence, the main harvest technology developed was based on high capacity self-propelled forage harvesters (SPFH) equipped with a special cutter-head. These SPFH are capable of harvesting at an effective rate between 40 and 120 t wet matter (WM)/h with an engine power between 300 and more than 600 kW, and an investment cost between $450,000 and $750,000. The larger SPFH can harvest 15 to 40 ha per day, depending on yield. In reality, SRWC plantations have developed at a relatively small scale in many cases, with average plantation areas of 5 ha in Sweden and typical areas of 3 to 10 ha in England. There is a currently a need and a technology gap for small-to-medium size harvesters, capable of harvesting a wide range of SRWC, especially larger stems (50 to 100 mm diameter), at a rate of about 20 t WM/h which would allow harvesting 3 to 8 ha per day. A small semi-mounted willow harvester (JF192) was operated by a 78 kW tractor and evaluated in a willow plantation. It harvested continuously at an average rate of 15.8 t WM/h, and had effective rates between 8.9 and 11.6 t WM/h when considering time to change hauling tractors and other normal delays (field efficiency from 56 to 73%). It produced filamentous wood chips and could not process adequately stems larger than 50 mm at the point of cut. A medium-size pull-type forage harvester (PTFH), operated in stationary mode with a 94 kW tractor, was fed willow stems up to 98 mm in diameter. It produced sharply cut wood chips, at an average rate of 28 t WM/h with a peak of 38 t WM/h. A novel cutter-head adapted to such a PTFH would be expected to process continuously at least 30 t WM/h with a 150 kW tractor, and have an effective rate of at least 22 t WM/h. Filling such a technology gap would be desirable for future development of SRWC.

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