How Cork City Council can move on from its robotrees fiasco

Irish Examiner

2 days ago

There has been a lot of misinformation and misconception thrown into the public domain recently regarding the 'death of the robotrees'.
It's time to put the record straight. But where to begin?
The very best way to get clean air in St Patrick's Street in Cork is to remove the sources of the pollutants. In other words, prevent all road transport driving along there. To start with, you need to ban all combustion engines… then later all vehicles, because tyre wear also releases the small particles that can kill us or put us into hospital.
Cleaning up polluted air is, very much, a second-best strategy. My own way of thinking about this process is to imagine brewing a cup of tea. And then adding a drop of milk. Then trying to take all the milk out. Impossible. In other words, don't add the milk in the first place!
Real trees, bedding plants, and 'CityTrees' on St Patrick's Street in Cork. Prof John Sodeau recommends none of the above as filters for toxic particles released by exhausts and tyres, saying chest-high hedging would be relatively effective — with the caveat that any level of particulates above zero can harm our health. Picture: Larry Cummins
Air cleaning devices like the robo trees (also known as CityTrees or moss walls) were therefore unlikely to prove very effective in removing the small toxic particulates and nitrogen oxides released from road transport to the air.
Starting in 2018, CityTrees were tested in Amsterdam.
By 2019, they had been removed because they proved useless. Many other European cities had the same experience. There is even a Wikipedia page devoted to the history of CityTrees. Now we know the end result is just the same for Cork.
The question is — why did Cork City Council undertake such an 'experiment' starting in 2021, given that the approach was not innovative or novel, and studies had already been published to show the devices were a total failure when located in the real world?
Of course it's good and forward-thinking to try new things and experiment to improve our environment. But not if you know the approach is unoriginal and furthermore does not work.
Whatever the council's initial motivations, there was absolutely no need to throw money down the drain over the last four years for running costs.
Two of the City Trees, generally referred to as 'robotrees', on Grand Parade in Cork. They were intended to filter harmful pollutants out of the air. Picture: Larry Cummins
The irony is that Cork houses the leading laboratory in air pollution chemistry in Ireland at UCC. Why did they not contact them — especially as the council apparatchiks involved in writing the National Transport Authority proposal had no appropriate scientific background in air science?
If they had phoned me, then I think I could have come up with a better way of achieving their clean-up aims in a couple of hours.
My answer would have been focussed on hedging the streets; not planting trees as has recently been suggested. That is because trees are not effective in removing small toxic particles and nitrogen oxides from road traffic emissions. Their main function in the urban environment is to remove the greenhouse gas, carbon dioxide, and to beautify the surroundings.
Hedges could help
Nature can still be the answer, but in the form of chest-high hedges.
These act as a physical barrier to the small, toxic particles released by exhausts and tyres from reaching pedestrians. Such a height is particularly effective for protecting small children and babies in prams, who are especially vulnerable. Although it should be noted that any amount of small particulates above zero can harm our health.
So, no matter how low the levels in Cork City are, they can still kill or give us cardio problems, promote asthma attacks, or cause cancer.
Cork City Council officials and then lord mayor Colm Kelleher speaking to media at the cluster of City Trees on St Patrick's Street in August 2021. Picture: Larry Cummins
Sadly, for whatever reasons, council representatives and employees have kept on defending the robotrees rather than owning the mistake. But things can be made good, in my opinion.
Firstly, the council should make an apology to the tax-paying public for wasting money on a device that was known to not work. Then they must learn the lesson of always consulting scientific experts on matters arising outside internal expertise. Then for the public to forgive.
Air pollution science is complicated. The CityTrees were badly named: They were never designed to do what real trees do for our atmosphere and our climate. But we should still keep planting trees.
The ultimate answer to help improve air quality in the city is simple. Ban all road transport driving along St Patrick's Street. Instead, run communal electric trolley buses like they do in Geneva. Or build a Luas, as in Dublin.
Finally, local authorities should lead and innovate by all means possible, but additionally use proven approaches to meet the complex environmental challenges we face today.
• John Sodeau is emeritus professor of chemistry at UCC