This project was initiated to provide technical assistance to the Alberta wood drying industry. The specific objective was to identify opportunities to improve product quality through modification of the drying schedules. Seven mills representing almost 50% of the solid, softwood lumber production in the province were selected for the project. All mills provided a great deal of cooperation and commitment to the project was excellent. In general, lumber drying operations in Alberta are in good physical condition and operating personnel have a sound knowledge of basic drying concepts.
In general, drying schedules were found to be quite harsh. the specific concerns at most mills related to too rapid a heat-up rate and extremely low relative humidity at the end of the drying cycle. Most of the schedule modification called for more gradual and controlled heat-up rates with higher wet-bulb temperatures. The objective of this modification is to avoid setting up conditions othat promote variability in moisture content from board to board. Higher relative humidity is required at the end of the drying cycle to avoid over-drying faster drying boards. Achieving a reduction in final moisture content variability and a higher overall average moisture content should be the objective of drying schedule modifications.
Mill visits were used not only to review drying schedules but also to conduct a brief inspection of drying practices and equipment. It would be unproductive to identify schedule modifications if there were obvious shortcomings in other areas of the operation that would make it difficult to implement or over-shadow the effect. The primary concern with drying equipment is the leakiness of the structures. A common recommendation to mills was to tighten up kiln doors and walls in order to retain more moisture in the kiln environment. Another area of concern was related to lumber handling operations. Most problems in this area could be addressed through educating and training staff working at stackers, handling material in the yard, or preparing loads for the kiln.
Logging and log storage practices at all of the mills visited has a serious and detrimental impact on the drying operations. At most times of the year, operators are having to deal with a wood supply that has a mix of initial moisture content conditions. Most mills seem to manage the small percentage of balsam fir in their mix effectively. Some future gains may be achieved through refined presorting techniques that take into account initial MC variability as well as differing drying characteristics between species.
The objective of this project was to determine the most effective, environmentally friendly treatments which will protect value-added lumber produced from Alberta wood species from fungal discoloration. This report presents information on selected sapstain control products and the efficacy results after a four-month storage period.
Over 0.5 million bone-dry tons of bark residues are produced annually in Alberta. Stricter regulations are now being invoked by environmental agencies with regard to disposal of bark residues by landfilling or burning in beehive burners. Hence it is highly important to find alternate uses for bark waste in the form of higher-valued products. The present study describes the manufacture of bark boards, using high-temperature pressing, without the addition of synthetic adhesives. Internal bond strength and linear expansion values for spruce and pine bark boards fell within the range of requirements for the grades of interior particleboards in the CAN 3-0188.1-M-78 standard (Interior Mat-formed Wood Particleboard). Although the bending strength values for the bark boards were below the bending requirements in the CAN 3-0188.1-M-78 Standard, the requirements could easily be met by applying thin overlays to the bark boards. This would also enhance their appearance. The boards exhibited excellent durability properties when tested using a 2-hour boil test. An important environmental advantage of bark board would be the absence of formaldehyde emission since the board is made without urea formaldehyde resin. It is likely that volatile organic compounds (VOC's) would be emitted in the high-temperature bark board pressing process and these would need to be controlled or trapped in some way, possibly by passage through a biofilter using bark as a medium.
The objective of this report is to review published research and provide an overview of the available technology for improving the properties of OSB. Computer searches were made of Agricola, Chemical Abstracts, CAB Abstracts, PCForest and TreeCD. In addition, lists of reports were requested from research groups known to have worked in the area. This report deals first with alternative treatment processes and their effects on the physical properties of the board and second with the performance of the treated products. The second section discusses only those treatments which had acceptable effects on board properties. In terms of practicality, economics and optimum physical properties of the finished board, the best treatments appear to be powder or concentrated liquid additives at the blender using certain combinations of preservative and adhesive. Borates are effective for protection against decay and termites in applications protected from the weather such as sheathing. As yet, no treatment has been developed which will provide long-term performance in ground contact. For fire retardant performance vapor boron treatment of the finished panel may be the best option. Further work is required on processes to improve dimensional stability of OSB.
Over the past five years a number of factors have come together to revive interest in treatment of Canadian softwoods with borates. These include opportunities in overseas markets where termites are a problem and the recognition of borate-treated framing as an environmentally acceptable alternative to soil poisoning and house fumigation. Pressure treatment followed by a short diffusion period is now the favoured approach since it is much faster than the old dip-diffusion methods. If Alberta sawmills are to take advantage of this new market opportunity they must be able to effectively treat spruce-pine-fir (SPF). This is not a simple matter due to the low permeability and low moisture content of the heartwood of spruce and pine. The study reported here was designed to compare the treatability of SPF with CCA and borates and to examine ways to improve borate treatment of SPF. Process factors considered were wood moisture content, pre-steaming and surfactant additives. Contrary to expectations, dried rather than green pine and fir appeared to be the best options in terms of treatability with borates but a two-week storage period was still required after pressure treatment with both 4 and 8% solutions to meet American Wood Preservers' Association standards. Based on the rate of movement of borate, dried spruce would be expected to meet the AWPA penetration requirement after 6 weeks storage. British Wood Preserving and Damp-Proofing Association specifications were achieved in dried spruce, pine and fir immediately after treatment. Neither pre-steaming nor the addition of didecyldimethyl ammonium chloride (DDAC) gave any detectable benefits in terms of preservative penetration in alpine fir and lodgepole pine. There was, however, a detectable improvement in treatment of spruce resulting from the addition of DDAC to the treating solution. A summary table of recommended treatment options was developed as a result of the research undertaken in this project.