VINEYARDS use approximately fifty per cent of all agricultural posts in Australia with the majority of pine posts used in agriculture being treated with copper-chromium-arsenic (CCA) timber preservative. For many years CCA was treated as relatively benign and its use was widespread. Most people knew that it should not be burnt, and if it was the ash should not be applied to gardens or farmland.
In the new era of environmental and chemical awareness, with much better detection systems and the inevitable affect of time and gradual decay, or careless disposal, CCA materials are attracting much more attention. All three of the constituents of CCA are toxic. Arsenic raises toxicity and social responsibility concerns at the source mines in China. Concerns continue about its use in public parks and backyards, where it appears in fences, decks and outdoor furniture, and in trellis and fences on farms.
Perhaps the most current and pressing issue is the final disposal of CCA in landfill. Chromium is not much less of a concern for human health, animals or plants, although copper is generally only a serious problem for aquatic life.
Health and environmental concerns have influenced the banning of CCA from organic farms and playgrounds, and regulators are placing more restrictions on storage and disposal of CCA timber. Over time we have introduced a huge volume of CCA material, primarily posts, into the environment, and as they age they are becoming a much greater component of the waste stream.
Incineration of CCA treated timber is prohibited in Australia due to the high concentration of toxic metals in the ash. Therefore the main method for disposal of CCA is on site burying or removal to a landfill site, with some potential for environmental harm from leaching of chemical from the timber into soil, streams or groundwater. As a result, many landfill operators no longer accept industrial quantities of treated timber posts.
Australian regulators are concerned about potential for CCA contamination of soil and have observed the restriction, and in some cases banning of the product in Germany, Japan, Scandinavia and some US States.
The US Environmental Protection Agency has encouraged a reduction in exposure to arsenic and CCA-treated timber products are being phased out for domestic use. In SA for instance, the Environmental protection authority prohibits burning or burying of posts, and takes an active interest in storage of large quantities. If sufficient numbers of posts are held, they recommend bunding and covering or wrapping heaps.
How many posts are there?
As vineyards posts age they become brittle and more susceptible to breakage from machinery impact. Annual replacement rate of posts in a vineyard may be as high as five per cent in new vineyards, rising to over 10 per cent as posts age. Within five years, six million broken posts will require disposal annually, equivalent to over 100,000 cubic metres, approximately the annual amount of waste deposited in a landfill catering for a population of 120,000 people.
Assuming that a vineyard has a span of 25 to 30 years, there will be a replanting peak around 2024 at which time somewhere between eight and 16 million obsolete CCA-treated posts will require disposal each year, in addition to the six million posts requiring disposal as a result of annual breakages. Based on conservative estimates, that equates to the landfill volume required to dispose of a year’s waste from a population of 140,000 people.
While most critical attention is currently applied to disposal, a full consideration of the sustainability of agricultural materials should include a whole life cycle evaluation. From this perspective, CCA and Creosote are both poor performers, due to production of the source materials for the active substances, manufacture and formulation of the preservatives, application (wood treatment) the service life of the product and waste disposal.
– Tim Marshall