As countries from India to Ethiopia plant millions of trees to combat global warming, one German company has a much smaller idea.
Berlin-based Green City Solutions plans to clean the air of local emissions from gasoline and diesel engines, by planting millions of tiny mossy trees in cities.
Moss works similarly to trees in filtering pollutants out of the air very effectively. To speed up that process in specific neighborhoods, Green City Solutions has developed a giant park bench topped by a mossy structure with remote-controlled fans that can accelerate the airflow through the moss in particularly smoggy sections of cities.
Two of the City Trees are already operating in Oslo, Norway. as well as in six different train stations in Germany. The company plans to install 15 of its new City Trees in Berlin next year with funding from the European Commission.
Green City Solutions City Trees use moss to filter air
Green City Solutions City Trees use moss to filter air
While moss is particularly effective at filtering out the types of nitrogen oxides and particulate matter produced by urban buses and delivery and sanitation trucks—and diesel passenger vehicles—it is also particularly sensitive to water and light conditions.
By connecting its City Tree benches to the Internet, Green City Solutions can remotely control watering, for example on particularly warm days. Sensors on the City Tree monitor the condition of the moss and call for what is needed to make it grow.
Before installing the City Trees, the company conducts extensive site analysis to balance the locations between heavily polluted areas and those with enough shade for moss to thrive. Urban canyons on streets between tall buildings are ideal environments.
In addition to cleaning the air, the moss City Trees provide a very localized cooling effect for those on the benches when the fans are on, by drawing air through the cool moss. The effect can address localized "heat islands" in cities.
The moss trees can also be used inside buildings, such as the Berlin train station, where 300,000 people transit and shop every day, alongside indoor railroad tracks.
