With whole tree chipping there is the potential to recover the complete above ground biomass from the trees. This method leaves no material on the ground, and 100% of the tree is chipped. We say above ground because this method does not include the stump and root system which are below the ground. For information on stump harvesting see the stump hogfuel supply chain.
This method fells trees without delimbing or crosscutting them. The trees are left on the forest floor for a summer season to allow the trees to dry and the green needles to desiccate and drop off. A terrain chipping system is then used to chip the trees, and the chip transported from the forest to the end user.
The initial harvesting is done by a chainsaw operator. Trees are felled only, with no cross cutting or delimbing. The chainsaw operator carries out a line thinning only, as the operator cannot physically carry out a selection between the lines as the trees are much to heavy to be carried into the line. The selection thinning is carried out with a mechanised feller buncher after the trees felled in the line thinning have been chipped. This selection thinning usually takes place the following year.
During harvesting, the chainsaw operator fells all the trees in the line in the same direction so that all the tree butts are in the same direction. This is the same method for the feller buncher, which fells the trees, pulls them into the line and lays them down so all the butts are facing the same direction.
The trees are left on the forest floor for a summer season to allow the trees to dry and the green needles to desiccate and drop off. Chipping is done using a terrain chipping system, comprising of two machines: a terrain chipper (with a collection bunk), and a chips forwarder. The system may comprise of purpose built forestry machines for this work, or may be a tractor with a specially designed chipper attached to the 3 point linkage, and a collection trailer attached to the front (the tractor operates in reverse). In this case the tractor may shuttle the chips to the roadside once it is full, or may employ a second tractor with a trailer to do this.
The chips forwarder drives into the forest, chipping as it goes. The chipper mounted on the forward facing end of the base machine. A grapple is used to feed the trees butt end first into the mouth of the chipper. The chips are blown into the bunk at the rear of the machine. Once full, the chipper tips the chips into the chips forwarder which extracts them to the roadside.
When the forwarder, or tractor trailer, extracts the chip to the forest roadside, it is best for the chip to be transferred directly into a waiting transport trailer. Although not necessary this prevents contamination of the chip with any road stone or soil if left on the ground, and any losses of chip. Having a truck waiting to be filled is not efficient, so systems can be used where many roll-on roll-off trailers are delivered to the site and are collected as they are filled.