A waste of money or a key part of cleaner air? The CityTree debate
St, Pieces Described Of As Furniture On Patrick's Are Smart The Cork Street City, Citytrees
Loud controversy erupted this week over five new high-tech structures filled with moss which were installed in Cork City to combat pollution while providing public seating.
The CityTrees, now known locally as ‘robot trees’, cost €350,000.
They were paid for through a €55m National Transport Authority fund announced under the July stimulus plan to support pedestrians and cyclists.
Both the cost and the concept exercised many people this week and the clamour of criticism somewhat clouded the fact that this week Cork City Council became the first local authority in Ireland to launch a Clean Air Strategy, containing many benefits other than the CityTrees.
CLIMATE & SUSTAINABILITY HUB
Air pollution kills up to 1,300 people in Ireland each year, according to the Environmental Protection Agency.
And the CityTrees aim to ultimately reduce this death toll and make cities safer places to live, Simon Dierks, marketing lead with Green City Solutions, the company that designs and manufactures CityTrees said.
CityTrees are designed to support, not replace, actual trees, he said.
“The idea is to support nature with technology. It’s a combination of biology — the mosses — and IOT [internet of things] to support the mosses to be capable of doing their magic, even in a habitat that is not their natural one.
“Like David Joyce from Cork City Council said, this is a site-specific solution. We are one part of the puzzle in Cork’s clean air strategy.
“The CityTrees are not ‘robot trees’, there are living organisms in there. These living mosses cool the air and clean the air with the great benefit that these biofilters are never full. So there’s great benefit and little waste. That’s why this is a sustainable solution.
He said that figures posted online which compared the pollution-sucking potential of one CityTree to 275 real trees were out of date, referring to an older model with a much larger surface area.
A €2m fund from the EU allowed Green Solutions to develop the CityTree product from 2018 to 2020. It now incorporates more technology to better manage the mosses and capture data.
"It’s not fair or accurate to use almost 300 trees as a comparison. We say that we can filter the amount of air in one hour that corresponds to the breathing volume of 7,000 people.
“I don’t really like the comparison to trees because people are afraid that this is the next evolutionary level of trees. That’s not the case and that’s not what we’re aiming for. We do not want to substitute trees. We actually help trees.
“A CityTree is not an artificial tree, it is not a robot tree. It is a biotech filter.
“Trees can do outstanding things and mosses can do outstanding things. The two live together in the forests.
“Trees in urban areas suffer from air pollution, they can’t grow well or purify the air. But a CityTree is made for installation in the city centre where there’s no soil, no place for the roots to expand, no light for the trees to grow.
“I heard people say you could plant 10,000 trees with the money, which is not true. You can’t plant 10,000 trees in the city centre. The infrastructure makes that not possible. So our idea is that CityTree works and functions in places where real trees can’t grow. And these places are the places where air pollution is high."
He said that CityTrees are now in London, Newcastle, Germany, and Portugal, as well as Cork, but they could be installed all over Europe.
The company was founded in 2014. It is based in Germany and currently employs some 35 people.
Studies conducted with the Institute for Air Handling and Refrigeration in Dresden and the Leibniz Institute for Tropospheric Research found a filter effect of 53% at 1m distance.
In addition, at a distance at 1m, the CityTree was measured with a cooling effect of 4C.
A filter effect on fine dust concentrations (PM1 to PM8) was also found to reach about 82% on average by a study conducted with ILK Dresden.
But Dr John Wenger, professor of chemistry at University College Cork, who specialises in atmospheric chemistry, air quality, and climate change, said that other independent studies found that CityTrees only lead to a 15% reduction in particulates in the immediate vicinity of the structure with no discernable benefits to air quality overall.
"And that fits in with expectations," he said. "The size of these walls of moss is not that large. So they’re never going to have a massive impact just because of the size.
“It’s a mistake to think that they can do anything to improve air quality except raise awareness," Dr Wenger said.
“The volume of air in the city just can’t be sucked through these things. It can only have a very local effect, you really need to be sitting underneath them to get the benefit of the clean air.
"So to pay €350,000 for that is really a bit of a waste of money. I think the money could have been spent more wisely on other ways to reduce air pollution."
He said that urgently reducing our reliance on vehicles and burning solid fuels is the most important way to clean up the air.
CSO figures show that 50% of people use cars to travel less than 2km — a distance that most people could easily walk or cycle.
"The best way to reduce pollution is to reduce emissions. That means less journeys by car, cleaner transport, more cycling, more walking.
"We know that air pollution in Cork during the winter months is worse when people are burning wood and peat and coal in fires. So there are things we can do to reduce air pollution but CityTrees are not one of them."
Dr Wenger said that despite this week's controversy, Cork City Council has been doing "the right things" to tackle air pollution.
"It has been investing in cycling and walking infrastructure, in the greenways, in protective cycle lanes to make cycling safer, creating pedestrianised zones.
"If you read the Cork City Air Quality Strategy, a lot of these good things are in there.
"They are the first local authority in Ireland to issue an air quality strategy. They are making good progress and they do have good plans."
Dr Wenger said that erecting more moss walls around the city, particularly by parklets, would be welcome to boost air quality but that these could be installed relatively cheaply.
"The problem with CityTrees is just that they’re so expensive. I think that’s the problem.
"The idea that they have the sensors and the screen is good to gather data and raise awareness.
“But I just think the cost is what appalled everyone. We could spend that money much more wisely I think."
CLIMATE & SUSTAINABILITY HUB