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Analysis of the treated wood market for agricultural and horticultural uses in New Zealand

By Boris van Bruchem, David Evison and Clemens Altaner, December 2020.

Download SWP-T114 (pdf)

Executive summary

This study analysed the treated wood market for agricultural and horticultural uses in New Zealand. Treated wood refers to fence posts for stock and crops, kiwifruit pergolas, vineyards posts and other horticultural supporting structures. Radiata pine (Pinus radiata) is the predominant species used in these industries and requires chromated copper arsenate (CCA) preservative treatment for outdoor application. This research is pertinent as there are concerns about CCA treated wood disposal, while there has been no publicly available analysis of the market. The information presented here will aid the New Zealand Dryland Forests Initiative (NZDFI) and elucidate the importance of the small dimension log resource.

Three sources of data were used to produce independent estimates of the market:

  1. a use per hectare estimate
  2. a manufacturers’ estimate
  3. a resource use estimate

It was estimated that approximately 6.9 million m3 of CCA treated wood is currently present in the agricultural and horticultural industries using the use per hectare method. This presents a significant disposal liability, with policy and a country-wide disposal strategy potentially required. Annually, based on sector expansions and replacement rates, ~290,000 m3 per year is used. Themanufacturers’ method estimated a range of ~270,000 m3 to ~310,000 m3 per year based on information from two independent CCA organisations. Lastly, the resource use method estimated ~390,000 m3 per year based on forest grower surveys.

The market is most likely between approximately ~270,000 m3 to ~310,000 m3 per year, as the resource use estimate presumably overestimates as survey responders indicated that house pile, pulp log, saw log and firewood volumes were included. The use per hectare estimate may also be an overestimation as non-wood products such as plastic and metal posts were not accounted for although experts indicated that these products only represent a small proportion of the market.

From the NZDFI perspective, the organic sector estimate of ~6,000 m3 per year to ~14,000 m3 per year is relevant. The lower estimate is based on a conservative expansion rate, while the upper estimate uses a high expansion rate, indicating the range. Further work regarding the feasibility of the NZDFI alternative eucalypt products is appropriate.

Concerning the small dimension log resource, the importance to forestry companies tends to depend on regions. Roundwood producers are concentrated in the Nelson, Central North Island (CNI) and Northland regions which are areas with low fertility soils typically producing trees with less taper and smaller branches. The requirements for roundwood products are reasonably strict and prices generally do not justify their production in comparison with the main competition of export pulp and K grades. This was especially true for forests located near ports.


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