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Scion has been looking for environmentally friendly bio-based timber treatments against fungi attacks.

Dr Tripti Singh from Scion explains more about this project to Alison Balance in this RNZ audio: Bio-based timber preservatives.

Duration: 12:53

Radiata pine is widely used in timber framing and cladding for houses in New Zealand. Common timber preservatives used include copper, arsenic, chromium and boron, but there’s growing pressure to find more environmentally friendly alternatives. Tripti Singh from Scion has been investigating a range of possible bio-based alternatives.

Decay fungi

The main focus of the research is decay fungi that cause rot in timber. The goal is to come up with ways of treating the timber so that it doesn’t suffer the effects of rot. The two main drivers are consumer demand and regulatory demand for products that do not create an end-of-life disposal problem.

Bio-based compounds

Tripti works with natural compounds that are already being used in other industries, which include lavender oil, Mānuka and henna extracts, orange or lemon skins, chilli juice and horticultural and agricultural waste products like avocado skins.

Testing in the lab

Tripti tests the compounds against decay fungi in Petri dishes. If they show activity against the fungi, she treats small wood blocks with the compounds after the blocks have been kept at a certain humidity for 2 weeks. The blocks are leached (saturated with water) for 14 days and then exposed to fungi for 6 weeks. The blocks are weighed before and after to see if the fungi are eating the wood or not. She tests for three brown rot fungi that prefer cellulose and one white rot fungus that prefers lignin. Radiata pine has both cellulose and lignin. The biggest challenge is fixing the compounds in the wood so that it doesn’t leach out when saturated.

Field testing

Tripti says they have already tested 100 compounds, and three have shown pretty good activity on pieces of timber. The next step is to test the compounds in field sites. Scion has four sites that have different rainfall, UV and soil conditions. It will require 2–3 years of field data to confirm the lab results. She hopes to have a bio-based product on the market within 2–3 years.

Programme details: Our Changing World

    Published 19 August 2013