Weed killer wreaking havoc on New Zealand's grass cuttings

Friday, 14 September 2018

The Sunday afternoon rumble of mowers might be the sound of spring, but a toxic element lurks in the Kiwi lawn.

Our addiction to weedkillers is the dark side to the manicured greenery that has been a corner of Kiwiana ever since settlers converted bush to meadows and rural dwellers moving to cities tried to recreate a piece of the countryside in the suburbs.

New Zealand's addiction to weed killers is sending tonnes of freshly cut grass to landfill each year.

The lingering effects of herbicides mean tonnes of grass clippings are an unloved by-product of lawn mowing, destined for landfill instead of returning to nature as compost.

Despite national legislation cutting down the number of herbicides available on the retail market, traces of the chemicals are still being found on household lawns. As a result, any compost made from clippings can cause stunted growth or distortion in house plants.

Paul Evans, chief executive of WasteMINZ, an organisation which advocates on waste and contaminated land management issues, says grass clippings often have to be separated from green waste to be composted on its own, or sent to landfill.

Marlborough District Council solid waste manager Alec McNeil with lawn clippings, which are later sent to landfill.

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Auckland Council's general manager of waste solutions Parul Sood says Aucklanders were responsible for disposing of their green waste, and this included grass clippings.

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WasteMINZ chief executive Paul Evans says grass was often separated from green waste to be composted on its own or landfilled.

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'There are approximately 19 commercial green waste composters in New Zealand, [and] just over half of these separate out lawn clippings and compost these separately,' Evans said.

Grass clippings being dumped at Marlborough's Waste Transfer Station.

'In some cases, where composters can't separate lawn clippings out effectively, they have to refuse to accept them.'

Evans said composted grass could be used as daily cover on landfills to reduce odours, pest attraction, fire hazards, and prevent litter and dust from being blown around the site.

McNeil said about 926 tonnes of grass were landfilled in Marlborough last year.

While lawn clippings could also be sold back to turf manufacturers, this could perpetuate New Zealand's herbicide problem, he said.

Marlborough District Council solid waste manager Alec McNeil said herbicides did not break down during the composting process.

'It's going to be there for a good two or three years before it will actually break down … that's what makes them so successful,' McNeil said.

McNeil said in an ideal world, grass would have no herbicide contamination and would be composted alongside green waste.

'But the problem is, how do we get to a point where we can assure ourselves that that's happened?' McNeil said.

'If we mix the grass with the green waste and it is contaminated, it will ruin all of that green waste compost as well.'

Even if compost could be created from the region's grass, McNeil said there was no long-term market for the product.

'At the moment, we just don't have a consistent market that will take it [compost], which is ironic as we're a primary industry in organic material,' McNeil.

'I think the big thing about the sustainability in the longer term is we need to have a market for the product or there's no point doing it.

A Wellington City Council spokeswoman said Southern Landfill, outside Wellington, received about 5000 tonnes of green waste a year, of which 'no more' than 5 per cent was grass.

'All of this is put into our composting process on site,' she said. 'Our process operates in accordance with the compost soils and mulches [New Zealand] standard.'

While the Southern Landfill had 'no issues' composting grass clippings, areas that processed a lot of grass had a history of contamination from the herbicide Clopyralid.

Agcarm chief executive Mark Ross said the nutritional benefit of composting was 'undone' if there was Clopyralid residue in the compost.

'This can be financially devastating for a commercial grower and disappointing for a home gardener,' Ross said.

A Christchurch City Council spokeswoman said lawn clippings were often not collected by the council after mowing in parks, as the turf benefited from the nutrients provided.

She also said the council owned an organics processing plant, so clippings were received as green waste, not waste to landfill, and turned into compost.

The Marlborough District Council waste collection service did not collect green waste or grass.

Residents would take their grass to Marlborough's Waste Transfer Station, at a cost of $36 per metre cubed, and the clippings were then expelled to Bluegums Landfill at a cost to council of $95.52 per tonne.

About 926 tonnes of grass where landfilled due to possible herbicide contamination at Bluegums Landfill, in Marlborough, last year.

'At the moment we can't make a product that's economically unattractive to the industry,' McNeil said.

Councillor Mark Peters asked McNeil at an assets and services committee last week whether the council should encourage residents to use their grass clippings as compost.

But McNeil said he thought grass composting was best removed from residential areas, as it often smelled.

Auckland Council's general manager of waste solutions Parul Sood said Aucklanders were responsible for disposing of their green waste, and this included grass clippings.

'[People] can do so either by composting in their garden, paying a licensed garden contractor to collect it for composting, or taking it to a composting facility,' Sood said.

Sood said while the council did not know how much grass was landfilled in Auckland, about 110,000 tonnes of both residential and commercial green waste was sent to landfills each year.

A Ministry for the Environment spokeswoman said while landfills accounted for 5 per cent of New Zealand's greenhouse gas emissions, there was no comparable figure for composting, as many people composted at home.

Environmental Protection Authority (EPA) general manager of hazardous substances Fiona Thomson-Carter suggested people thinking about using herbicides in their home garden consider other options, such as weeding and mulching.

Concern at the contamination risks has added to criticism of the Kiwi lawn tradition.

Last year, the Auckland Botanic Gardens called on New Zealand gardeners to consider alternatives such as flowering meadows, noting that even the smell of freshly cut grass signals a hazard to the environment. The chemicals released in lawnmowing interact with air pollutants, worsening smog.

But whatever the future holds for the front lawn, there's always The Front Lawn - the 1980s Kiwi theatrical/music act featuring Don McGlashan, Harry Sinclair and Jennifer Ward-Lealand.