Summary
¦ Bois Durables de Bourgogne has six partners, including Groupe Ducerf.
¦ Output of thermo-treated timber, including ash, poplar and Douglas fir as well as oak is 2,000m³.
¦ Investment to date is €2m.
¦ Installation of a further kiln will double output.
Oak is, of course, a naturally high performance timber. But according to a group of companies in Burgundy, France, thermo treatment takes it to a new level; making it more likely to be used in a wider range of applications and enhancing its consumer appeal. That’s why they’ve jointly invested €2m in a thermo treating joint venture called Bois Durables de Bourgogne (BDB), which is now building up to capacity of 2,000m³ a year.
The partners behind the operation are glulam and wood building specialist Barlet Frères and sawmillers Margaritelli France, Groupe Petitrenaud, Scieries Réunies de Chalonais, Fuyet Père et Fils and, perhaps the best known in the UK, Groupe Ducerf.
The plant is in Vendenesse-lès-Charolles and is staffed by personnel from Ducerf. According to the latter’s export director Florence Perrucaud, the prime motivation for setting up the operation is of course commercial: to broaden the partners’ product offer and increase sales. But it’s also intended to enhance the performance characteristics and increase the competitiveness of locally-grown timbers so they can substitute more inherently durable tropical species (and BDB processes ash, poplar and Douglas fir as well as oak). That, said Ms Perrucaud, helps the timber trade “reduce freight miles and shrink its carbon footprint”.
Clean and green
“It’s also a green process in its own right,” she said. “It doesn’t involve the use of chemical treatment and there’s no waste. Currently the boiler used is gas-fired, but the plan is to change to wood fuel when capacity is increased to a sufficient level in the next few years.”
The BDB project took root in 2006 with a feasibility study and technical trials undertaken with the Arts et Métiers ParisTech university in Cluny.
After looking at a range of systems, it was decided to head to the Nordic heartland of thermo processing and opt for technology from Jarvik of Lahti, Finland.
Subsequent trials involved treatment of oak, ash, poplar and Douglas fir for exterior cladding, plus samples of the first three species for interior decorative and joinery applications. The full-scale 1,200m² plant, which is already processing 1,000m³ a year, was purpose-built – and, naturally, is part clad in thermo-treated timbers.
Prior to treatment, the wood is seasoned and kiln-dried according to criteria established during pilot testing. In the thermo kilns, in a process taking 30-60 hours, it is progressively heated up to a maximum of 190°C to 250°C, depending on species and colour required, with steam used to keep the timber supple and prevent burning and cracking.
Enhanced properties
The process alters the physical characteristics of the wood by reducing the level of hydrophilic hydroxyl molecules. This makes it more moisture resistant and less prone to movement. Density is slightly reduced due to the 5-6% moisture content, but fungal resistance, durability and insulation properties are all enhanced.
“It also gains colour, which many feel makes it more attractive,” said Ms Perrucaud. “Dark woods emerge resembling more exotic species, while paler species are a warmer ‘bronzed’ shade. As the timber is treated throughout, it’s also uniformly coloured across its thickness, so there’s no problem cutting or machining.”
Ducerf has brought out a range of exterior and interior use products using timber thermo treated at BDB. The former are branded Côtéparc and comprise oak and ash decking boards and panels, deck components and landscape products and cladding in oak, ash and poplar.
“Because of the aesthetics of the thermo-treated timber, we are also using it under the sub-brand Thermoline to make our Patchwood finger-jointed panels and Panoplot edge-glued panels for worktops, furniture and interior joinery,” said Ms Perrucaud.
Cost comparisons
Thermo-treated sawn timber from the BDB partners sells for between €300-350/m³, plus handling/transport, while Ducerf’s decking is priced at €40-50/m².
Some thermo-treated product is priced comparably with its conventional competition – the oak decking, for instance, is pitched at the same price as ipe. But where there is a premium, it’s clearly not proving an obstacle.
“Customer reaction is good and we’re selling across the EU and as far afield as the Far East,” said Ms Perrucaud. “But the business will really start next year when we’ll have more stocks produced over the winter. In particular, we will build up supplies of decking for the spring and summer sales period.”
There are plans too to increase the capacity of the BDB plant to 4,000m³ a year by installing another kiln. Highlighting its commitment to developing the market long term, it has also teamed up with other producers, notably Dumoulin Bois, to set up a trade body for the French thermo-treatment sector; L’Association Bois Modifiés Thermiquement. This, in turn, is working with the FCBA technical institute in Bordeaux to establish a French thermowood certification scheme to provide end users and consumers with a guarantee that the material has been processed to a set standard, plus an assurance on quality and durability.
• For more contact florence.perrucaud@ducerf.com
