Council frowns at continuing use of clopyralid



Chemical-infected lawn clippings delaying compost

More than 3000 tonnes of compost is being stockpiled at the Timaru District Council’s Redruth recycling centre unable to be sold until exhaustive tests and expensive extra handling and turning procedures show that it has overcome a chemical put into the composting stream by Timaru District residents.

And as the stockpile grows, the council’s senior waste management officer Ruth Clarke and contractors Transpacific Industries are frowning at the reason for the growing mountain of compost – despite extensive awareness campaigns some residents are persisting in using a now-restricted weed spray on their lawns that contains the active ingredient clopyralid.

Clopyralid is a compost-poisoning chemical that was ordered off the domestic market in August 2008 by the Environmental Risk Management Authority (Erma) after a reassessment of the risks to the community.

It is so persistent in the composting process and biologically so active that traces as low as five parts per billion in composted garden waste were enough to cause deformities in tomato plants and potatoes.

But its slowness to degrade biologically means lawns sprayed with proprietary lawn sprays containing clopyralid months ago are still producing lawn clippings that are seriously contaminated.

Ms Clarke said this week the problem chemical was unusually persistent and only required miniscule amounts to render entire batches of compost unsaleable until extra measures had been taken to degrade the chemical.

“To degrade it adequately, contaminated compost has to be matured for an extra long period of time which entails holding it in windrows until such time as the testing shows there is none left,” she said.

“This may take up to eight months, or even longer, and involves continual turning and moistening to keep the compost bacteria active.

“The cost involved in this, as well as in continued testing, is significant and amounts to a processing loss for the contractors, the council, and ratepayers.

“It also impacts on the availability of product as the compost must be held on site for much longer than would normally be the case,” she said.

Clopyralid is found in a range of lawn sprays and its presence is clearly shown on the container labels.

Depending on the clopyralid product, labels will include, “This substance is not to be used on turf” and “Treated vegetation shall not be disposed of at any green waste recycling centre.” “Eco-toxic herbicide. Not for use in home gardens.” “ Do not use for treating turf that will be mown and the clippings used for making compost; or made available for collection for, or deposited at, a municipal green waste recycling depot.”

However, some Timaru residents are not listening.

The message to them is that by putting clopyralid-contaminated clippings into the green bin they are ruining the process for others and pushing the ultimate cost of compost higher than it needed to be.

“If clopyralid is used, please ensure the lawn clippings are not disposed of via the green waste system,” Ms Clarke said.

“There are alternative methods of disposal such as using the clippings as a mulch around shrubs on the same property, but best of all is mowing treated lawns with a mulching mower so that clippings are retained on the affected lawn,” she said.

Timaru branch manager for Transpacific Industries Ltd Peter Martin, said even though Erma withdrew clopyralid from the market, sprays containing the chemical could still be purchased in bulk.

“And we are also aware that there are garden sheds with older stocks of the banned spray on their shelves.”

“We take compost quality very seriously and we will not let any compost leave the site until it is shown to be clear of the herbicide by laboratory analysis and we have grown our own tomatoes in it to ensure it is free of the dreaded chemical,” Mr Martin said.

He said people with sprays containing this active ingredient who were unsure what to do with them could bring them to the transfer station to have them disposed of free of charge.

ENDS

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