Information – Miscellaneous
Alternatives to tanalised wood posts
Tanalised/ copper chromium arsenate (CCA) treatment is the almost exclusive preservative treatment for soil contacting and exterior wood especially for pine (excluding that used for building construction), in New Zealand. Typical examples include livestock fence posts, and perennial crop (vines and tree) trellis / support systems.
However, there is growing concern, both within New Zealand and internationally, about problems with ‘tanalised’ / Copper Chromium Arsenate (CCA) treated wood. These include the use of heavy metals as a preservative, the potential for them to leach into the soil and wider environment, especially in production systems with high concentrations of posts, e.g. vineyards, the health effects on people contacting the posts, e.g. fencing workers and children in playgrounds, and with the disposal of treated timber at the end of its life (landfill being the only current safe option). Due to these concerns, organic agricultural production standards, both in NZ and overseas, have or are banning the use of CCA, and similar wood treatments.
Farmers and growers are therefore increasingly interested in using, or are being required to use, alternatives to CCA treated wood.
As part of the response to the banning of CCA wood in organic production standards, in 2010 OANZ (Organics Aotearoa New Zealand) undertook an analysis of the alternatives to CCA treated wood posts and published the results as the “Over The Fencepost Alternatives to CCA (Copper Chromium Arsenate) treated wood”. This document is provided by the FFC for general information purposes as a number of the posts / manufacturers listed in the report are no longer available, and there are also new posts / manufacturers that are not listed. You are recommended to check other sources of information, e.g. adverts in the trade press / the web, for other potential posts and suppliers.
At the time the OANZ ‘Over the Fencepost’ report was published, a grape cultivar / variety genetic library was being established at the BHU. The opportunity was taken to use non-CCA posts in the vineyard as a demonstration project.
The following posts were used in the vineyard.
|Post name||Manufacturer / supplier / website link|
|UltraPost||Industrial Tube Manufacturing Co Ltd|
|EcoPost||Industrial Tube Manufacturing Co Ltd|
|Wood Shield||Wood Shield Pty|
|Eco Trellis||NZ Tube Mills|
|IR posts||Integrated Recycling Ltd (AU) / Pukekohe Timber & Packaging (NZ)|
|Recycled Plastic Post||Empak Distribution|
|Wallaba Posts||BBS Timber|
The post collection is a demonstration rather than a trial, so no comparisons are being made among the different posts. Also inclusion of any particular post is not an endorsement of that post by the BHU or FFC nor is the non-inclusion of any post a rejection of that post by the BHU or FFC.
However, anyone is welcome to view and assess the posts for themselves during normal working hours. The vineyard is sited at The BHU Farm, The Hort Research Area, Lincoln University. Google map. You can also email Charles Merfield for more information.