Whole-tree Chipping
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See also Chipper & Full-tree Logging
Whole-tree chipping is the process of chipping by-products generated from commercial logging operations into boiler fuel.[1] Any type of organic matter that is combustible and left behind in the forest from logging can be chipped and burned as a source of fuel or grinded to produce finer chips for pulp. The industry term for this woody material is biomass. Biomass includes the tops and limbs of felled trees, cull logs, stumps, dead and rotten trees, and non-merchantable timber. The process is called whole-tree chipping because portable chippers are used for chipping every part of the tree.
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[edit] History
Prior to the 1950s, most wood chips at sawmills were piled up or burned. Most paper mills produced their own chips too. It was the development of debarking equipment in the woods and at mills that changed the nature of chip processing and use. The ability of debarking equipment to strip the bark off logs culminated in the production of much cleaner chips. By the early 1960s, satellite chip mills began to pop up and expand throughout North America right up through the ‘80s, especially in the southern United States.[2] As chipping operations grew, the demand for whole-tree chips for pulp fiber and boiler fuel also increased. This explains the growing acceptance of whole-tree chipping operations in the woods starting in the ‘70s. By 1980, it was estimated that over 750 portable chipping units were used in whole-tree operations within North America.[3]
[edit] Process
Every year, forest harvesting produces massive quantities of waste wood. In addition, a good portion of trees in a forest stand is often too small or otherwise unsuitable for commercial use. One method of salvaging unusable forest resources into usable product is chipping non-merchantable trees and slash. The chips produced are used as a source of wood energy to power pulp and paper mill boilers. Finer chips produced from limbs and tops of trees can also be used to make pulp for paper.
In particular, the introduction and practice of whole-tree chipping has opened up possibilities in forestry, especially within the last decade or so. For example, on pine tree plantations, trees are being thinned out much earlier in a rotation with whole-tree chipping.[4]
A typical whole-tree chipping operation will begin with the mechanical felling of unwanted trees either with chainsaws or feller bunchers. A grapple skidder or cable skidder is then used to drag trees and slash over to a portable whole-tree chipper (WTC). The stems get processed inside the chipper while the limbs and tops of the pines trees get fed to a grinder. Grinding the tops and limbs in this manner results in a much finer quality of chip. The chips are then blown from the grinder and the whole-tree chipper into large enclosed trucks or trailers.
Roadside chipping and off-road chipping are variations of whole-tree chipping that originated in Scandinavia and involve mounting a mobile chipper on a truck, tractor, or forwarder. The chips get discharged into an exchangeable tip-up bin or blown directly from the chipping machine in a road-haulage rig. The chippers used in roadside or off-road operations are heavier and stationary.[5] One advantage of these methods of chipping is that soil erosion is minimized because whole trees are carried to the roadside instead of being dragged along the ground by skidders.
[edit] Advantages of Whole-tree Chipping
Whole-tree chipping has many advantages. From an economic perspective, whole-tree chipping yields a higher return on investment since every part of the tree gets used. It also leaves behind a much cleaner forest stand.[6]
The practice before whole-tree chipping was introduced into the woods was to burn waste wood and slash. An article featured in the October 1999 issue of the Logging & Sawmilling Journal cites that, as far back as 1999, the B.C. government recognized the inherent value in wood waste reclamation projects and supported such programs through the introduction of salvage stumpage fees. The end result was less wood debris left behind in the forest and better air quality since wood debris was no longer burned. Salvaging wood waste through whole-tree chipping also proved to be an effective way to control bugs and insect infestation such as the pine beetle because whole-tree salvage chipping replicated the final phase of harvesting. The stand got completely cleaned up and this assisted in preventing bugs such as the pine beetle from flying away and rerouting elsewhere.[7]
[edit] Equipment Used
[edit] References
- ↑ Elliot, C. Thomas, Chen, Kao and Robert C. Swanekamp. Standard Handbook of Powerplant Engineering. McGraw-Hill Professional, 1998.
- ↑ http://www.esf.edu/for/germain/Lec07%20FOR373%20chipping%20operations-20b.pdf
- ↑ Wenger, F. Karl. Forestry Handbook. Wiley-IEEE, 1984.
- ↑ Thinning With a Whole Tree Chipper. Tilda Mims. Alabama Forestry Commission. 2008-11-10.
- ↑ Sjaak Van Loo, Jaap Koppejan. The Handbook of Biomass Combustion and Co-firing. Earthscan, 2008. pg 64
- ↑ Thinning With a Whole Tree Chipper. Tilda Mims. Alabama Forestry Commission. 2008-11-10.
- ↑ McDonald, Paul. In the Chips. Logging and Sawmilling Journal. October 1999. pg 29 –31.
