Canadian Forest Service Publications
Optimizing Drying of Mountain Pine Beetle Wood. 2005. Oliveira, L.C.; Wallace, J.; Cai, L. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, BC. Mountain Pine Beetle Initiative Working Paper 2005-12. 30 p.
Available from: Pacific Forestry Centre
Catalog ID: 25509
This report presents the methods and results for the industrial and laboratory tests carried out for the project “Optimizing Drying of Mountain Pine Beetle Wood”. The results can be used by sawmills to assist them in choosing cost effective drying strategies to recover value from post- mountain pine beetle (MPB) wood.
Meetings with industry representatives in the early stages of the project surveyed the impact that MPB is having on the manufacturing of lumber products. These meetings were used to fine tune the research deliverables and obtain feedback and commitment for the field activities.
The main problems identified by industry representatives that they attributed to the MPB were: (a) increased variation of the initial moisture content, not only among pieces of lumber, but also within the piece, along the length (b) increased difficulty in estimating the correct kiln shutdown time (c) over-drying as a consequence of incorrect kiln shutdown (d) lower grade recovery (e) non-uniform final moisture content.
Post-MPB (bluestained) sapwood demonstrated substantial increases in permeability and diffusion coefficients (at 50°C, 70°C and 90°C). The increase in tangential permeability was 8 to 25 times and the radial permeability was 6 to 23 times when compared to non-stained wood. The increase in the diffusion coefficients ranged from 34% to 76%. These increases will allow post-MPB sapwood to dry faster than non-infested sapwood but after drying, the post-MPB sapwood will equalize faster than non-infested sapwood, ultimately producing a piece of lumber with uniform moisture content.
Air-drying of post-MPB-infected wood during the summer months significantly lowered the average initial moisture content and standard deviation in two locations: Quesnel and Vancouver. The best results for lumber with initial moisture content below 20% were found when employing typical industrial schedules and processing (planing) 24 hours after drying. For lumber with initial moisture content ranging from 20% to 30%, the best results were found when the lumber was air-dried for one week, followed by typical heat-treatment schedules and planing one week after drying. The best results for lumber with initial moisture content greater than 30%, were obtained for lumber dried according to typical industrial schedules and planed one week after drying. These results will allow sawmills to target different strategies for moisture sorted post-MPB wood.