Mobile Moss Structures Can Filter Our Dirty City Air

A German startup says its CityTree technology is more efficient at purifying air pollution than 275 trees.

Think globally, scrub locally.

That could be the slogan for a new technology coming out of Europe that uses high-tech mobile moss structures to scrub pollutants from the air on the hyperlocal scale. Dubbed the CityTree, each mobile installation removes dust, nitrogen dioxide, ozone gases and other particular matter in its immediate vacinity.

The idea is to place CityTrees in urban outdoor areas where people tend to congregate the most — city parks or commercial plazas, for example — and let the specialized moss cultures do what they've been doing on their own for a few million years and counting.

The CityTree project is already gaining momentum in Europe and Asia, where clusters of CityTrees have been popping up in Brussels, Oslo, Paris, and Hong Kong. According to the German startup company behind the technology, Berlin-based Green City Solutions, each CityTree can demonstrably improve air quality within a radius of 50 meters (about 150 feet) around each individual installation.

Despite the name, the CityTree isn't really a tree at all. It's a rectangular platform of densely packed moss culture, vertically housed in a weatherproof casing around four meters tall, three meters wide, and about two meters deep. Optional park benches can be attached on either side. In an effort to make the structure financially viable for buyers, each CityTree can also be used as an analog billboard or commercial sign space. Just affix your ad or company name to the grid beneath, and you've got a living, breathing billboard.

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According to Green City Solutions, there's plenty of hard science behind the environmental efficacy of their technology. Internal studies suggest that each moss structure — with a total area of about 3.5 square meters (38 square feet) — filters an amount of airborne particulates that is the equivalent of 275 trees.

“The CityTree is based on a biotechnology, a special moss culture which has the ability to attract air pollution from its surroundings and to convert it into its own biomass,” Denes Honus, CEO and co-founder of Green City Solutions, says in a company video. “The moss literally eats air pollution.”

click to play video
Green City Solutions

Honus says the CityTree is an economical option for city planners and urban architects. Compared to planting and maintaining 275 trees, the CityTree is 95 percent more cost effective and requires 99 percent less space, according to company research. The moss also tends to cool the surrounding air in warmer environments.

Like any respectable 21st-century object, each CityTree is integrated with IoT technology – that's the emerging designation for the ever-growing network of physical objects known as the Internet of Things. Each CityTree has internal sensors that monitor the health of the moss as well as the environmental performance of each unit.

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The CityTree is designed to be adaptable and mobile. Property managers can plug the CityTree into existing water and electricity lines for automatic irrigation. Or you can add extra modules like solar panels and rainwater tanks that provide independent irrigation and power. Each installation can be moved and reassembled in about eight hours.

While pricing varies, CNN reports that each CityTree runs about $25,000. That cost includes installation and consultation on the optimum location to set up each CityTree. Green City Solutions is currently testing a peripheral ventilation system that would actually direct local air flow directly to the moss screen. So, for example, if an adjacent intersection is fuming up your corporate plaza, strategically placed fans and CityTrees could scrub the air before it wafts over an area where people gather.

There's no official word yet on when CityTrees might begin popping up in American cities, but the company is committed to bringing the system to cities in developing countries where air pollution is a significant problem.

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