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Above left: Tanalith MF has predominantly been used across Europe for the treatment of cladding PHOTO: FORECO Above right: Timber is now being heralded as a go-to low carbon construction material
with specifiers and end users that hold the perception that preservative treated wood is ‘bad’ because of the use of chemicals. This is a view that completely contradicts my own personal experience as, during my working life, I have witnessed a number of significant changes in the industry. These changes include the advancement in smart pressure treatment operations with targeted treatment software, the demise of some stalwart preservative systems and key actives, and the emergence of tough EU legislation. Like any construction material, wood preservatives are continually evolving with specifier and regulatory demands. Whilst the aim is to provide long-term protection against decay fungi and insects for less durable timber species, this must be done in a way that minimises any risk to the environment, human and animal health. In our world today, all wood preservatives are subject to the highest risk assessments. They are also applied as efficiently as possible via modern plant operations that utilise plant management software, such as Arxada’s Auto-Treater. In fact, modern preservative systems and application technologies provide real opportunity to promote the benefits of treated timber to debunk archaic misconceptions. Imagine a world where pressure treated timber can be specified and used in an appropriate use class with a full Life Cycle Analysis (LCA) to produce a cradle-to-grave Environmental Product Declaration (EPD), so every pack or piece can provide its own carbon footprint – I think that day is now here!
THE EVOLUTION OF ACTIVES Across Europe there are a number of wood preservatives available. When specifying treated timber, it is important to understand how the chemistry and the carrier behind the wood preservative is suited to the timber’s end-use application.
Treated timber used in Use Classes 1 and 2 is transitioning across Europe to non-metal preservatives that are based on organic
actives. These wood preservatives provide an envelope of protection around the timber. Some design professionals put the case as to why internal joinery with little risk to wetting needs to be preservative treated. Whilst the level of risk to wetting is low, these are important components to structural integrity. By using treated timber, longevity and durability will be assured, requiring less embodied energy in the maintenance and upkeep.
In 2020 Arxada brought to market an updated formulation of its traditional Vacsol Aqua low-pressure treatment. The revised formulation of water-based Vacsol 6118 is both metal-free and VOC-free. This means timber treated with Vacsol 6118 can be recycled or reused at end of life (subject to local waste regulations). In addition, when working on the revised formulation we challenged ourselves to reduce the carbon footprint of transportation by designing Vacsol 6118 as a concentrate, eradicating the need for bulk tanker delivery.
For Use Classes 3(c) and 3(u) – coated and uncoated – non-metal-based wood protection technologies are being developed that can be applied through high-pressure impregnation. Whilst these new metal-free technologies provide a slightly lower service life than the more traditional copper-based wood preservatives, they do come with a number of benefits including recyclability and/or reuse at end of life and being VOC free. In 2021 Arxada launched a metal-free version of Tanalith E high-pressure treatment – Tanalith MF. To date, Tanalith MF has predominantly been used across Europe for the treatment of cladding to help with the sustainability credentials of projects. In higher-risk Use Class 4 applications, where the treated timber will be in-ground, two types of wood preservative are available: water-based and oil-based. Water-based wood preservatives containing copper such as Tanalith E are universal preservatives used for all use classes, whereas oil-based systems such as Tanasote S40 are designed for high
performance industrial timbers such as poles, railway sleepers and long-term agricultural and landscaping projects where performance is key.
It is therefore important to educate the
market on the utilisation of actives used in the different water-based and oil-based copper formulations as they impact the overall environmental credentials. The more modern water-based formulations are paired with powerful organic co-biocides, which means that smaller quantities of copper are used, helping with waste classification at end-of-life.
DRIVING TREATED TIMBER LCAS AND EPDS
If preservative treated timber provides longevity and durability, and requires minimal maintenance, then this has a positive impact on the overall carbon footprint and can be used to correctly inform professionals who instinctively have a bias against the use of preservative treated wood. With the modern actives used in a number of wood preservation products, the re-use of treated wood is also helping to overcome these challenges and can be brought to life through the use of LCAs and EPDs.
At Arxada we are investing in both EPDs and LCAs for our wood protection technologies. We are finding that customers outside the UK are utilising these to help drive the use of treated timber in their regions.
For example, in the Netherlands there is a carbon levy on sectors, including the built environment, and treaters and manufacturers of treated wood products are utilising our Tanalith E cradle-to-gate assessment to formulate a full cradle-to-grave EPD. We are hoping that treaters in the rest of Europe will soon be undertaking their own EPDs and using the data provided on our chemicals to help educate on the specification of treated timber compared with alternative materials, including modified wood, hardwood and untreated wood. ■
www.ttjonline.com | May/June 2023 | TTJ
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