A RECENT trial of using eco-friendly weedkillers without the controversial chemical glyphosate in Cardiff has shown mixed results.

Contractors working for Cardiff council usually use a glyphosate-based weedkiller on streets and pavements in the city.

But environmental campaigners have raised concerns glyphosate could be carcinogenic and also harm biodiversity.

In March last year the council announced a trial using two alternative weedkillers, although early findings show both are more expensive and have a greater impact on the environment.

An update on the trial was given to councillors on the environmental scrutiny committee on Thursday, January 13.

Cllr Peter Bradbury, cabinet member for culture and leisure, said: “We have tried to go down a more environmentally friendly route of disposing of weeds, and we’ve had varying results. The council is trying to move away from more toxic pesticides. The trial we’ve had, we haven’t had a lot of data back, but the data we have had back is mixed, to say the least.”

“We started this trial with a view of phasing out glyphosate herbicide, not to keep it. It was started with a view of ‘is there a more effective and environmentally friendly alternative product to the one we’re using’. Actually what we’ve found is that it has been a mixed picture.”

The council looked at the cost of each product as well as the time spent for contractors to apply the weedkiller, the overall environmental impact, the number of complaints from local residents about weeds, and the quality of each weedkiller judged on photos of treated areas.

The trial saw contractors use New Way Weed Spray in Riverside and Pontcanna, which contains acetic acid and leaves a vinegary smell in the air shortly afterwards, and Foamstream in Pontprennau and Old St Mellons, which uses hot water and a biodegradable foam made from natural plant oils and sugars.

According to early trial findings, New Way Weed Spray and Foamstream were more expensive than glyphosate, and had a worse environmental impact. Areas with New Way Weed Spray also saw more complaints from residents than Foamstream and glyphosate, while New Weed Spray and Foamstream were judged both less effective than glyphosate.

Dr Dan Jones, managing director of Advanced Invasives, a consultancy, told councillors: “Glyphosate has been proven to be safe and highly effective. Its use has been framed as a toxic herbicide, but actually, relatively it’s very safe. We’re talking about very limited use.

“When we look at the costs, the Foamstream can’t be deployed at scale. You also have a very low environmental impact of glyphosate, compared to very high carbon emissions related to Foamstream.”

He added much of the environmental impact and carbon emissions from Foamstream came from heating water before the weedkiller could be used.

Full details of the findings of the trial are expected next month in a cabinet report, as well as whether the council decides to continue using glyphosate-based weedkiller or alternatives.