Speciality Chemicals Magazine NOV / DEC 2022 | Page 18

Wood preservatives for industrial heavy duty timbers in the modern era

Dr Stephen Uphill , technical lead for global industrial products , explains how Arxada use cutting-edge analytical tools to identify potent biocides

Forests are a renewable resource and a net sink of greenhouse gas , locking CO 2 in growing trees and storing it while in-use . The use of wood is key towards a circular economy and the European Green Deal . Effective wood preservation , with a long-service life against wooddestroying fungi and insect attack , means that treated timber can store carbon for decades longer than untreated decay-susceptible wood Creosote is a robust , long-lasting , efficacious wood preservative that has been used for over 150 years for the preservation of timber used in heavy duty applications , including railway sleepers , utility poles and agricultural posts . Currently over 1,500,000 m 2 / year of timber are treated with creosote in Europe alone . 1

Figure 1 - EN252 field test data from Gainesville , USA , 65 months after installation Note : Error bars show the range of ratings for each group of stakes .
The regulatory regimes in place today across Europe – the EU and GB Biocidal Products Regulation ( BPR ) - require a rigorous evaluation of both the environmental and human health toxicology of wood preservatives for both active substances and biocidal products . Creosote is classified as toxic , persistent , bioaccumulative and carcinogenic , and it meets the exclusion criteria for biocidal active substances . Whilst it is currently authorised for use in Europe , it is now facing potential restrictions in the renewal of this authorisation , which will severely limit its applications . Arxada has developed Tanasote * S40 , a modern BPR-authorised wood preservative , as a viable , effective alternative for creosote . Tanasote
S40 delivers extended service lives in critical applications , helping keep wood as a viable material for heavy duty applications .
Use of metagenomics
In the development of new formulations , the Arxada wood development team used metagenomic DNA analysis to screen how active ingredients perform against wooddecay organisms . Metagenomics uses DNA-sequencing platforms to characterise the microbiome , that is the presence and proportion of organisms in the environment under test . This technique allows examination of how the microbiome is altered in wood samples treated with various active ingredients . The team used an Oxford Nanopore GridIon sequencer , which is part of the newest generation of sequencing platforms . This platform reads DNA sequences one base at a time as the DNA passes through a tiny hole , the ‘ nanopore ’. The resulting sequences are compared against Arxada ’ s custom DNA database , which allowed us to identify fungi , bacteria , archaea , viruses and other organisms in our samples . Metagenomics analysis makes it possible to assess how well our active ingredients work to inhibit the growth of target organisms that cause wood decay . It also provides novel insights into organisms that contribute to active ingredient detoxification . By studying the interactions between preservative ingredients and the wood microbiome , we can formulate robust wood preservatives more rationally to deliver long-lasting treated wood .
18 SPECIALITY CHEMICALS MAGAZINE ESTABLISHED 1981