THIRTY-FIVE delegates from the sawmilling and timber-treating sector made the journey to Sweden for the annual Wolman Conference.
The event has become an established feature for sections of the UK timber trade, giving companies a chance to catch up on the latest issues surrounding timber preservative treatment and visit foreign mills and their treatment operations.
The setting for the conference was Linnaeus University in Växjö, Småland region, which has a department of forestry and wood technology that teaches 750 students every year.
Presentations gave delegates an opportunity to assess developments with the Industrial Emissions Directive (IED) and incising technology as a way of increasing the penetration of preservatives into timber.
IED Update – First up was Willie Clason of Bridewell Consultancy updating on the IED the EU’s main instrument governing pollutant emissions from industrial installations, including timber treatment plants.
Existing treatment installations had until July last year to obtain a permit, with operators qualifying for an IED permit if they have the potential to produce more than 75m3 of treated timber in a 24-hour period.
Mr Clason explained that permits have to take account of the plant’s whole environmental performance including emissions, waste, use of raw materials and noise, while permit conditions must be based on Best Available Techniques (BAT) contained in a BAT reference document (BREF).
But Mr Clason said it was not all plain sailing and there was consternation in the UK about how IED is being enforced.
He reported huge differences across EU member states on the number of plants reported with IED permits. Some countries just have a few plants with permits, while the UK has reported 240 plants.
Mr Clason said a lack of awareness by local regulators of BREF (still to be published by the EU), meant some local authorities had given plants tacit approval to continue operating without permits.
Other issues he raised included: • other industries being ahead of wood preservation on IED • terminology differing across Europe • permit fees (high fees in Scotland) • some operators self-restricting their plant capacity to fall below IED threshold and avoid paying for a permit • the higher environmental risk of creosote/ solvent based treatment compared to water-based treatments • verification that freshly treated wood is dry.
Until the EU BREF document is published it is down to each member state to operate its own regulatory controls.
“I think the UK will continue to run as normal with negotiated permits,” said Mr Clason.
“I think there will be no change [due Brexit] because the UK government can’t turn its back on environmental controls,” he said.
Laser Incising The next session by Professor Stergios Adamopoulos of Linnaeus University focused on laser incising as a potential method of improving the penetration of timber preservatives into wood.
Laser incising was first looked at in the mid-1990s, with the lasers creating deep pinholes in wood.
Problems encountered were carbonisation of the timber in the process, visible marks on the timber surface and strength loss. But more recent research has looked at the method in detail to try and overcome those challenges.
Research involved using a small defect-free sapwood spruce-fir sample and a pulsed laser class 4, Q-switched Nd YAG using a wavelength of 532nm to reduce thermal effects and carbon deposition in holes, with a pulse duration of four nanoseconds.
Laser incised holes were to a depth of 0.4cm, with a hole diameter of 1mm using two different laser patterns. The holes created were of a conical shape.
The first step was to avoid carbonisation of the wood on the 96 test specimens.
Results were good, with strength testing in drilled specimens showing a strength increase. “We were quite surprised about this,” said Professor Adamopoulos.
The samples’ modulus of elasticity in static bending and toughness remained
unchanged, while MOR and axial compression were even increased by the laser drilling.
Step 2 of research asked: can laser incising enhance penetration of oil-based and watersoluble preservative products.
The conclusion was the method led to a higher retention of the treatment but not as great as had been hoped.
Lateral penetration of CCB (chromate-copper- boron) and rapeseed oil immediately after impregnation was much higher (1.3 – 5.6 times better retention) than that of non-drilled specimens.
“This technology cannot change the world in terms of impregnation but we’ve still seen some improvement,” said Professor Adamopoulos.
The technology will need further testing, investment and research, he added.
Mechanical Incising – Mechanical incising was the subject of a presentation from the BRE’s Dr Ed Suttie. Mr Suttie said the first commercial incising of timber has been in 1910 in the US.
The BRE has been involved with incised timber testing since 1972, when a field trial was run in the UK using Russian whitewood, with research showing increased uptake of preservatives.
Early incised test samples were credited with a potential 55-plus year service life with the use of CCA treatment. Mr Suttie mentioned Ballycassidy’s Permapost product from the 1970s with incised ends.
“It was a fantastic product but it came at the wrong time,” said Mr Suttie.
But the advent of the ban on CCA treatment in the early 2000s was a big change in the UK timber treatments market. Some early fence post failures with post-CCA generation preservatives meant incising was being looked at more.
But market perceptions of incised timber was fairly negative at the time due to its surface appearance, concerns over added cost of production and sensitivity over price in a highly competitive market.
The BRE has since been involved with incised treated Sikta spruce testing, with test sites at its Elgin and Garston sites.
Mr Suttie said tests showed UK Sikta spruce had an increased uptake of preservative treatment compared to unincised product and also met treatment penetration and retention requirements, along with Scots pine, Douglas fir and larch.
Spruce treatment uptake at 18% moisture content (mc) was better than at 30-40% mc.\
Mr Suttie also said several rounds of testing of automatic, commercial incising technology showed several advantages, include reduced stresses in posts, uniform treatment penetration and improved performance of treated timber, though a slight strength reduction was also recorded.
The latest incising machine studies in several UK sawmills showed incising doubles the treatment penetration (for spruce) in the analytical zone tested and requirements for UC4 15-year service life were met. However, the results were more mixed for Douglas fir.
“The landscape has changed beyond recognition since 2003,” said Mr Suttie.
He said incised timber was now meeting with market approval, had Wood Protection Association Benchmark scheme recognition, while machines and products had established themselves in the market and consumers had accepted incised material.
“I do not want to say that timber has to be incised because we know that it’s species and end-use specific,” said Mr Suttie.
Bergs Timber Visit A visit to Bergs Timber’s Bitus timber treatment operation, which treats around 200,000m3 of timber per year, concluded the Wolman event.
Bitus site manager Henrik Egnell said as well as in-house treating for Bergs, the Bitus facility is also doing service treatment.
Mr Egnell said Bitus’ highest treating levels had been following the storms Gudrun and Per in 2009 at 225,000m3.
In 2016/17, Bitus will treat about 215,000m3 in eight pressure treatment plants and one oil treatment plant. Several different preservative products are used, including Wolman CX-8, which is a mainstay of many mills in the Scandinavian region. Some 70% of product treated on the 2ha site is destined for the UK market via large UK importers.
Delegates had the opportunity of talking with Wolman technical representatives about the company’s products and were shown the possibilities available with Wolmanit ProColor – colour additives which can be added in vacuum pressure treatment or dip treatment, with both pigment- and dye-based systems available.
Ralf Schulz, managing director of BASF Wolman GmbH, said the system of wood preservative, grey colour and surface finish, Wolman System Silvergrey has resulted in positive responses from architects.
“We have to get out of this green timber treatment corner and inspire the consumer,” said Mr Schulz.
Wolman’s full range includes product lines to cover Use Class 1-4 (including, Wolmanit CX and Wolsit EC and Wolsit KD, as well as fire retardant products such as Wolmanit Firestop and mould and sapstain protection in the Sinesto and Wolsin product lines.
Wolman gave delegates a run-down of all the various types of technologies available for improving timbers, including chemical and thermal modification, and highlighted their relative benefits and drawbacks.
Delegates were also given a detailed explanation of Wolman’s Royal process, a refining process for vacuum pressure treated wood which is designed to confer a high level of water-repellence, dimensional stability and durability to treated wood.
Only 24 hours after treatment in the Lowry process, wood moves into the Royal treatment process, in which it is boiled in hot linseed oil – made possible by use of a fast fixating preservative such as Wolmanit CX.
The result, Wolman says, is a treated timber product which is more durable than CCA-treated wood.
“The Royal process combined with Wolmanit CX-treated wood and the new Wolman System Silvergrey – this is how we can inject innovation into the market,” added Mr Schulz.
