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UC breakthrough in treating exports logs

UC breakthrough in treating exports logs

September 19, 2012

University of Canterbury researchers have made a breakthrough in treating export logs by heating them using high voltage electricity.

Timber exports are a major contributor to New Zealand’s export earnings. The Ministry of Primary Industries said more than 12.8 million cubic metres of logs with a value of nearly NZ$1.7 billion were exported through New Zealand’s ports last year. The majority of exports (NZ$1 billion) went to China.

Export logs are usually fumigated to rid the timber of pests, such as insects and fungi which could pose a biosecurity threat.

"Methyl bromide has been the most common fumigation used but there’s been a global drive to reduce, or preferably eliminate, its use," UC’s Electric Power Engineering Centre director Allan Miller said today.

"Methyl bromide plays a role in ozone depletion, and there are also concerns about potential health effects linked to its use.

Under the Montreal Protocol on substances that deplete the ozone layer, ratified by New Zealand in 1988, there are obligations to “refrain from use of methyl bromide and to use non-ozone-depleting technologies wherever possible.”

The ozone hole affecting the Antarctic and New Zealand is slowly healing due to the reduction of ozone destroying chlorofluorocarbons (CFCs) substances.

But ozone levels above Antarctica are projected to return to 1980 levels (previous to the ozone hole) after 2050. The Montreal Protocol means that emissions of ozone depleting substances (CFCs) have largely been banned worldwide. Ozone is present only in small amounts in Earth’s atmosphere. Nevertheless, it is vital to human wellbeing and ecosystem health.

UC researchers applied high voltage electricity between the ends of logs in tests, causing rapid heating of the log. A minimum core temperature had to be maintained for a minimum period to achieve eradication of pests.

"Heat treatment is accepted as a quarantine treatment for logs and timber being shipped to the USA and many other countries, but this is usually performed by dry heating in a kiln or heating with steam rather than heating directly with electricity," Dr Miller said.

During electric heating, care must be taken to avoid damage to the timber by overheating. This technology contains current monitoring and control to mitigate this.

The initial research by Dr Bill Heffernan, an Adjunct Senior Fellow in EPECentre and the Department of Electrical & Computer Engineering, was funded through the Stakeholders in Methyl Bromide Reduction consortium and the Ministry of Agriculture & Forestry Biosecurity New Zealand. Extra government funding has also been granted.


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