Air pollution is a widespread problem that has affected every area of our lives areas since the dawn of industrialization. But even as far back as the 13th century, the burning of sea coal in England filled the air with such sulfurous smoke that King Edward I decreed the burning or selling of bituminous coal punishable by torture and death.

Today, regulations in the battle for cleaner air are not as harsh, but the problem remains the same. In large urban centers and in Chinese mega-cities in particular, the issue is more pressing than ever before. We have all seen the images of cities engulfed by smog whose inhabitants can only brave the streets equipped with facemasks.

Not all air pollution is created equal, though. It can have a range of different sources – such as smoke, gasses, aerosols, fumes and odorants released through burning as a consequence of industrial production. 

In European countries alone, the number of deaths attributed to air pollution is thought to be many times higher than the number of people killed in traffic accidents. Globally the WHO estimates the death toll at an incredible 8 million – each and every year. And while increasing numbers of cities are kicking off clean air initiatives, no really effective approach has been found so far. Yet we all learned something in kindergarten that could help: Plants filter the air and release oxygen as a by-product of photosynthesis. Plant life is very limited in the concrete jungle though, where dense construction leaves little space to grow enough vegetation that could truly improve air quality. 

The Green City Solutions start up might have found the cure that would allow us to gain the upper hand over this global problem fairly easily. A team of four young men from Dresden, Dénes Honus, Victor Spittgerber, Liang Wu and Peter Sänger, brought together a wide range of skills from architecture and urban design to mechanical engineering and biology. Together they have created a product that is not just useful, but also extremely attractive. 

Their brain child is the CityTree, a verdant vertical wall covered with actual greenery. It filters the same amount of particulate matter as 275 trees but takes up 99% less space. Since the firm was founded in spring of 2014, the young entrepreneurs’ concept has garnered numerous prizes and awards. 

Vertical greenery with WIFI

“We take advantage of the very latest in biofiltration,” Peter tells us. He is the team‘s biology and gardening expert. “The CityTree is green on both sides. We use very special moss cultures not usually found in an urban setting and combine them with what are known as vascular plants. This combination is what makes the CityTree so efficient.” Ferns number among the vascular plants, as do some spices and herbs. These serve as the covering vegetation, the part of the CityTree passers-by actually see. City Tree owners can choose from a range of vascular plants that offer different features – green, flowering, or fragrant. 

At 4 meters tall and 3 meters wide, there is much more to CityTree than just the plants. The system also incorporates solar cells and an intelligent irrigation system. “We designed it to be easy to maintain – the integrated water tank does not need to be hooked up to the water supply, so you can set up a CityTree pretty much anywhere. It is outfitted with sensors that constantly monitor the plants’ water needs and determine whether the pumps should be switched on. The system can also communicate with the outside world. It sends out a message requesting a refill when the tank is empty, so you don’t need to monitor it at all. We do recommend checking on the Tree around once a month to make sure the plants still look good. That is pretty much it though.”

You can set up a CityTree pretty much anywhere.

The CityTree is much more than just a green eye catcher. It uses Internet of Things technology (IoT) for a whole host of other applications besides sending out an email asking for more water. The CityTree can also generate profit by displaying content – from the classic analog poster to a digital screen. The system allows for integrated iBeacons, serves as a WIFI hotspot, and can be used as an e-bike charging station. “Living” QR codes are also possible – the surface of the CityTree can be planted with a mix of illuminated pixels and plants to create the characteristic code pattern. And it is a nice place to sit and cools the surrounding air – making a CityTree a very attractive spot for pedestrians, especially during the dog days of summer. 

It's all about the moss

The first prototype took Peter and his partners around 18 months to complete. Given that they had to select the ideal moss from among the 11,200 existing species, this seems like an amazingly short time span. The perfect moss had to filter the air effectively, grow well on a vertical surface, and survive the direct rays of the sun. “We selected for the traits we needed bit by bit until we had identified a few ideal types of moss. We are now growing them ourselves under optimal conditions. The moss we use is extremely robust and can be used in urban environments and at temperatures ranging from -4o°C to + 5o°C. We have patented or are in the process of patenting our technologies. We also wanted to make sure producing CityTrees was sustainable. So they are primarily made of recyclable materials. The moss and vascular plants compost quite easily, and the aluminum and steel can be reused. The pots are made of “bioplastic”. All the components can be easily integrated into recycling processes.”

And while making a City Tree releases 4 tons of CO2, this is quickly recouped as a City Tree in operation absorbs almost 240 tons of CO2 per year. 

Despite the relatively brief development period, the team needed financial support to survive. All four founders invested their entire life savings in the project. In the first year they received funding from a start-up grant, 72,000€ that allowed them to focus solely on getting CityTree off the ground. “When the grant ran out, we went to a normal bank and took out a loan we are still living off of. We didn’t want to give up our independence in the very early phases of the venture by getting investors involved. We have continued to fund the project ourselves from initial sales and prize money,” Peter explains.