CityTree: A Mossy Wall That Has The Same Air-Purifying Effect As 250 Trees

Germany is installing “mossy walls” called CityTree – the world’s first bio-tech filter to quantifiably improve air quality – around their cities, mainly Berlin. A variety of mosses are capable of binding environmental toxins such as particulate matter and nitrogen oxides while producing oxygen at the same time. These CityTree’s contain nearly 2,000 pots of moss so imagine how much environmental toxins it binds!

The organic particles polluting the air get eaten (digested) by bacteria on the moss, according to the German makers of the wall. The purifying work of the 2,000 pots of moss along with their particle eating bacteria is equal to about 250 trees! A trial wall went up off Piccadilly Circus in London and it indicated that a single CityTree could remove the particulate pollution of 42 diesel cars every month.

Mossy wall eats as much pollution as 250 trees

  • Solar panels to power fans for a controllable ventilation technology that allows airflow to be intensified (meaning that the filter effect can be increased as required.)
  • A rainwater catchment system to supply a fully automated irrigation system for watering the moss.
  • IoT technology which delivers comprehensive information on performance and status as well as environmental data on the CityTree’s surroundings.

Mossy wall eats as much pollution as 250 trees

These 4-meter tall slabs can improve human health by consuming ultra-fine airborne particles that can travel deep into the lungs and pass into the bloodstream, posing a serious risk to health. Research suggests that particulate pollution is linked to higher death rates from respiratory illnesses and there are numerous studies that link dirty air to higher risk of mental disorders such as dementia, bipolar disorder, severe depression, and schizophrenia. One study even found that breathing polluted city air is the same as smoking a pack of cigarettes a day!

A dozen CityTrees are going up in Berlin for this reason. However, Ian Colbeck, of the University of Essex argues that “the ability of moss to collect air pollutants, especially heavy metals, had been known for some time but that given the scale of the problem it would be better not to emit pollutants.”

It’s clear that it would be better if no pollution was emitted in the first place. But because the complete elimination of everything in the world that emits pollution is not going to happen any time in the near future, it’s good to see solutions popping up that can help clean the air for people in the meantime.

Mossy wall eats as much pollution as 250 trees

Regardless, the mossy walls create a very pleasant ambiance and they also provide a pleasant cooling effect. Mosses store large quantities of moisture. That, combined with the considerably increased evaporation surface of the wall creates an immense cooling effect for the people around it.

The European Commission are funding Green City Solutions to install 12 CityTrees in Berlin with €1.5 million from the EU’s Horizon 2020 science fund. The initial 12 CityWalls in Berlin will serve as a pilot project to prove their effectiveness and could later be expanded throughout Germany and other EU nations.

Andrea D Steffen, 3 October 2019