By Chris Giles
It causes seven million premature deaths each year, making it the single largest environmental risk factor for individual health, according to the World Health Organization (WHO).
In urban areas, air quality is particularly problematic. More than 80% of people living in areas where pollution is monitored are exposed to air quality levels that exceed WHO limits. And given that two-thirds of the global population is expected to be urban by 2050, cleaning the air in our cities is an urgent matter.
An established way to reduce air pollutants is to plant trees, as their leaves capture and absorb harmful particles.
But planting new trees is not always a viable option.
For this reason, in several cities around the world, such as Oslo, Paris, Brussels and Hong Kong, theCityTree, a mobile installation that removes pollutants from the air.
The moss is in the air
EachCityTree It is just under 4 meters high, 3 meters wide and 2.19 meters deep, and is available in two versions: with or without a bench. Includes a screen with information or advertisements.
Berlin-based company Green City Solutions says its invention has the same environmental benefits as 275 real trees.
ButCityTree it is not, in fact, a tree: it is a moss crop.
“Moss crops have a much larger leaf surface area than any other plant. That means they can retain a lot more pollutants, ”says Zhengliang Wu, co-founder of Green City Solutions.
The huge areas of moss that are installed on each tree can remove dust, nitrogen dioxide and ozone gases from the air. The installation is autonomous and requires very little maintenance: solar panels provide electricity, while rainwater is collected in a tank and then pumped to the ground.
To monitor moss health, theCityTree It has sensors that measure the humidity and temperature of the soil and the quality of the air.
"We also have pollution sensors within each facility, which help monitor local air quality and tell us how efficient the tree is," adds Wu.
Its creators say that eachCityTree It can absorb about 250 grams of particulate matter per day and contributes to capturing greenhouse gases by removing 240 metric tons of CO2 annually.
A story of four friends
The history of CityTree dates back to 2006
While studying at the Dresden University of Technology in Germany, Wu met Victor Splittgerber, a mechanical engineer, and Dénes Honus, an architect. Upon graduation, they led a university workshop on sustainable urban design focused on new ways of tackling environmental problems in cities.
Four years ago, the trio met Peter Sänger, a graduate in horticulture production management, and the idea for the project was born. CityTree.
Today, the biggest obstacles they face are bureaucratic ones.
"We were installing them in Modena (Italy) and everything was planned and coordinated, but now the city is doubting the places where they can be installed for security reasons," explains Wu.
The team also plans to introduce theCityTree in cities in low-income countries like India, which tend to have high levels of pollutants.
So far, about 20 trees have been successfully installedCityTree, each of them at a cost of about $ 25,000.
Does this really fight pollution?
Gary Fuller, an air pollution expert at King’s College London, thinks the concept of an urban air purifier can be very ambitious.
"Even if you have a perfect air purifier, getting ambient air into contact with it is really difficult," he told CNN. Pollution from a car's exhaust, for example, spreads vertically a few kilometers into the air.
“It would be better to put efforts first in stopping the formation of pollution, perhaps cleaning up a city's bus fleet,” he adds.
The inventors ofCityTree they say they are aware of this and that is why they choose the location of each ‘tree’ very carefully.
“We intentionally choose places where pollution is high due to traffic and where air flow is limited. We are also testing a ventilation system to create our own air flow and thus be able to bring the contamination to the tree, ”they say.
Wu also says that theCityTree it is just one piece of a huge puzzle.
“Our ultimate goal is to incorporate the technology of theCityTree in buildings that already exist ”, he says. "We dream of creating a climate infrastructure to regulate what type of air and also what type of temperature we have in a city."