SFF Project Summary
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Last updated: 21 April 2009
- Final report [PDF 2.08MB]
- Report: Intermittent and continuous drying of red beech timber from the green condition [PDF 466KB]
- Flyer: Workshop on indigenous beech drying, August 2008
Project description
This project aims to demonstrate to New Zealand's beech industry the benefits of using advanced drying and processing technologies to dry the timber faster and improve its quality.
The issue/opportunity
New Zealand's indigenous beech species are perceived to be difficult to kiln dry and process on a commercial basis. However, similar hardwood species abroad are successfully kiln dried and marketed worldwide. This is primarily due to advanced technologies using steam and vacuum kiln drying processes. Thus, there is an opportunity to investigate these overseas technologies and apply them to the New Zealand setting. A significant improvement in beech processing efficiency would provide industry the incentive to increase the current production of dried-beech timber of 10000m3/annum to a sustainable 40000m3/annum.
The context/background
Non-recoverable degrade losses of 15% Red-Beech timber and 8% Silver-Beech timber are typically reported in the New Zealand beech-timber industry. On the basis of a sustainable annual production of 17000m3 for Red-Beech timber and 23000m3 for Silver-Beech timber, and a selling price of $1400/m3 (average of Dressing A and B timbers), these degrade losses equate to approximately $6.1 million per annum. Thus, there is a significant incentive to reduce degrade losses by using better drying and processing technologies. An added benefit of using these technologies would be faster timber drying and reduced holding times in timber yards. Any improvement in efficiency is necessary to maintain and build an indigenous forestry sector that is currently struggling commercially due to competition from imported timbers and furniture.
Methods
- Research the New Zealand and overseas literature on kiln drying, steaming and colouring of hardwoods
- Assess the commercial viability of these techniques for New Zealand's indigenous beech species
- Carry out practical trials to assess the applicability and financial returns of the new drying, colouring and steaming technologies for New Zealand beech processing
- Conduct two workshops for the local beech-drying industry. The first workshop will take place early on in the project and will give industry an opportunity to assess the domestic and overseas findings on the literature survey. In the second workshop, which will take place at the end of the project, the overall findings of the project will be presented to industry.
Prepare a best practice guide on the operational practicality and financial viability of the new technologies for the local industry.
Latest update
A drying test has demonstrated that one-inch red beech timber can be dried from the green condition with an acceptable degree of timber degrade in less than 3 months. The traditional method involves 6 months of air drying followed by one month of kiln drying. This test has shown that high initial moisture-content variations and differences in drying behaviour between boards results in unacceptably high final moisture-content variations of the dried timber. However, analysis of the data has revealed that presorting of beech timber into sapwood and heartwood classes and/or heavy and light classes with subsequent separate drying of these classes can significantly reduce these final moisture content variations. Another small-scale test in a 1m3 conventional kiln at Canterbury University has shown that equalisation is even more effective for reducing final-moisture content variations. The results of these tests will be presented at the International Drying Symposium this year. Subsequent drying tests will focus on optimising the schedules to reduce drying times further in order to increase the economic viability of drying beech timber from the green condition.
More tests have been planned to 1) test equalisation on an industrial scale, 2) determine whether pretreatments (hot-water soaking and steaming) are effective in reducing the drying time of beech timber on an industrial scale, and 3) investigate the difference in drying time between winter and summer cut timber. A tool is currently under development to enable the drying time of timber of any thickness and initial moisture content to be predicted. This tool will provide users with a guideline for drying red and silver beech timbers in the future.
A workshop is currently being organised, and will take place on 14 August. Please contact Dr Justin Nijdam for more details.
Update
A literature survey has identified several methods for successfully drying difficult-to-dry hardwoods. Overseas studies and current practices include air drying, pre-drying, kiln drying using intermittent and stepwise drying schedules, and vacuum drying.
Current practice in New Zealand is to air dry red beech timber from the green condition for up to 6 months before kiln drying for one month down to the desired moisture content. Domestic research on New Zealand beech species has shown that red beech can be dried intermittently from the green condition in a kiln without degrade of the timber in a shorter period of time. This method involves allowing the timber to relax by switching off heaters and fans in the kiln between periods of more intensive drying. The first intermittent drying trial involved 30 m3 of partially air-dried red beech from the West Coast of the South Island. This timber (one inch boards) was successfully dried in a dehumidifier kiln without drying degrade. Based on these promising results, a second trial was conducted using 40 m3 of freshly-sawn South Island red beech (37 m3) and silver beech (3 m3). This intermittent drying trial is three-quarters completed, and no drying degrade has thus far been observed, nor is it expected. The data from this test will be used to estimate drying times for intermittent drying schedules at various temperatures. In addition to this test, a continuous drying schedule is currently being tested in a conventional kiln at the University of Canterbury to dry 1 m3 of green red beech as a base case to compare with the intermittent schedule. Vacuum drying tests in the North Island and South Island are also being planned for the coming months.
A workshop, sponsored by the Sustainable Farming Fund, was held on the 15th of February and covered (1) a survey of domestic and overseas literature on best practices for drying beech and similar hardwoods, and (2) preliminary kiln trials into two promising methods: conventional (with stepwise changes) and intermittent drying. Several prominent members from academia and industry spoke including Robert Miller (MAF Indigenous Forestry Unit), who presented an overview of the beech drying project in relation to the development of a sustainable beech industry, and Robert Donnelly (University of Canterbury), who has a current SFF project (05/048), which is investigating marketing possibilities for the New Zealand beech industry.
