Cork City’s €400k 'robotrees' like using 'bathroom sponges in Midleton' to combat flooding

The four-metre high 'CityTrees' on Grand Parade, Cork City, use moss to filter pollutants from the air. File picture: Larry Cummins

An expert in atmospheric chemistry says the time has come for Cork City’s robotrees to be “junked”.

Emeritus Professor of Chemistry at UCC, John Sodeau, a founding director of its Centre for Research into Atmospheric Chemistry, said Cork City Council must accept that it got it wrong on the €404,000 CityTrees or moss walls project and simply plug them out and dump them.

“The deployment of the five robotrees to clean up Cork City air was the equivalent of using five bathroom sponges in Midleton main street to combat flood damage a couple of weeks ago,” he said.

“The consequences to local businesses in Midleton would surely not have been changed if the sponges had been there. Although five bathroom sponges would not have cost €400,000 to taxpayers. And there would be no running costs other than wringing the sponges out."

The CityTree devices, developed by German-based Greencity Solutions, were bought by the city council using NTA funding and installed at two city centre locations in summer 2021 as part of a post-covid ‘greening the city’ initiative. 

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The devices use moss to filter pollutants from the air. They also serve as a bench. But critics branded them ‘robotrees’ and a waste of public money.

A report to the council’s environment strategic policy committee on Tuesday said a city council-commissioned “performance study” on the devices, conducted by UCC in summer 2022, found “no consistent evidence for improved air quality” either on the CityTree benches or “in the immediate environs” of the machines, and that more detailed research is required.

On foot of the findings, officials plan to seek a research partner to undertake that extra research, pending a decision on relocating the devices.

Mr Sodeau said city officials can say “I believe, I believe, I believe" as much as they like but he said the question must be asked if it’s worth more taxpayers’ money to fund a third study for devices that have been “junked” in other locations.

He said:

For example, two months ago in September, Waltham Forest Council in London removed its two urban greening CityTree installations because they were covered in dead moss and therefore ineffective for improving local air quality.

He said an independent scientific study on the CityTree devices performed by the Leibniz Institute for Tropospheric Research in Germany a few years ago indicated a reduction of up to 30% for pollutant particles with indoor measurements, but no reduction figures for outdoors filtering were given other than stating, as expected, “the measurements were shown to be dependent on meteorological conditions”.

He said the UCC study on the Cork devices has proved inconclusive too.

Mr Sodeau said the fundamental answer to improving air quality is to stop the release of particulates and nitrogen oxides by banning all fossil fuel transport—including buses, trucks and taxis—and replacing them with electrified public transport, and to ban the burning of all types of solid fuel in the city and suburbs.

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He said it is unfortunate that the council’s good work on developing a clean air strategy has been overshadowed to an extent by the controversy over the robotrees.

Meanwhile, Green Party Cllr Oliver Moran has become one of the first Greens to support calls for the devices to be scrapped.

“The initial funding was from national sources, we engaged in research on them, but the ongoing costs are too much for the city to continue supporting without evidence of their benefit," he said.

“We should use the learning from them to innovate again and keep innovating."