From smog-sucking bikes to electric taxis and paint made of car exhaust, designers and architects are stepping up to address air pollution—the world’s single largest health risk. But a new air filter making the rounds in Oslo, Paris, Brussels, and Hong Kong shows that nature may be our best ally in this battle.
Essentially a moss-covered wall, each CityTree removes CO2, nitrogen oxides, and particulate matter from the air while also producing oxygen. A single tree is able to absorb 250 grams of particulate matter a day and remove 240 metric tons of CO2 each year—a level roughly on par with the air purification impact of 275 urban trees. Thirteen feet tall, with a metal frame, the CityTrees are easily installed in a public space, and they even have built-in seating at their base.
"Moss cultures have a much larger leaf surface area than any other plant. That means we can capture more pollutants," said Zhengliang Wu, co-founder of Green City Solutions—the makers of CityTree—in an interview with CNN.
They’re also relatively self-sustaining and tech-forward. The frame has built-in sensors to monitor soil humidity, temperature, water quality, and air quality. Solar panels power up the sensors, while rainwater is collected and later pumped into the soil.
Each CityTree costs about $25,000, and so far about 20 of the “trees” have been deployed.