Weeks into the first growing season after the initial coppice harvest, hybrid poplars near Stanwood, Washington resprout with multiple stems.
Harvest and regrowth of poplar feedstocks
A forage harvester with a woody biomass cutting head is used to harvest poplar trees grown for bioenergy. The harvester cuts and chips the poplars as it moves down the crop rows, feeding the chips into a truck that moves alongside or behind the harvester. The chips could then be taken directly to a biorefinery where they could be converted to bio-based chemicals or biofuels.
Poplars are harvested in a single-pass system where the trees are cut and chipped as the harvester moves down the crop row.
The remaining cut stump, often called a stool or root stock, sends up multiple shoots of re-growth for subsequent harvests. For biomass production systems, poplar is first harvested two to three growing season after it is planted. During this initial establishment period, the poplar will develop a strong root system that will encourage robust regrowth after the first harvest. Successive harvests will occur every three years for six or seven coppice production cycles after which the site would need to be replanted or restored for another use. Yields from coppiced production cycles will yield a substantially higher amount of biomass than the initial harvest, because the trees were primarily developing strong root systems during the first cutting cycle.
The forage harvester and woody biomass cutting head were developed for short-rotation poplar through a collaboration between GreenWood Resources, Inc., Case New Holland, and SUNY (The State University of New York). The harvester has two robust rotating saw blades for cutting the poplar wood and push arms to assist feeding the stems into the machine. The harvester can efficiently cut and chip stems that are four inches in diameter at a stump height of 4-6 inches. This system has successfully harvested trees at rates up to 100 green tons per hour.
Case New Holland’s FR 9000 series forage harvester with a FB 130 coppice header.