“I sat on the roof and kicked off the moss …”

                                ~ Elton John, Your Song

When I’ve been in downtown areas, particularly in the summer, I try to walk on the side of the street in the shade, since the temperature on the sunny side rises considerably. On the other hand, in the winter the sunny side is warmer, usually snow- or ice-free and where all the street people hang out — in the relative warmth.

Unfortunately, this accumulation of undispersed heat isn’t just uncomfortable, but adds to global warming. According to the EPA, “’Urban heat islands’ occur when cities replace natural land cover with dense concentrations of pavement, buildings, and other surfaces that absorb and retain heat. This effect increases energy costs (e.g., for air conditioning), air pollution levels, and heat-related illness and mortality.”

In nature, rock walls will accumulate a growth of lichen, per Wikipedia, “… a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship …” The lichen capture and use the solar rays to grow and produce oxygen like other plants do, thus combating global warming.

I often wondered why we couldn’t coat the walls of our buildings with something that would reduce the temperature and create oxygen, like lichen does. Well, apparently, others had the same thought. Journalist Emilie Chalcraft reports, “Scientists at a Spanish university are developing a new type of concrete that captures rainwater to create living walls of moss and fungi … Unlike existing vertical garden systems which require complex supporting structures, the new ‘biological concrete’ supports the growth of organisms on its own surface, according to researchers … The concrete contains a biological layer that collects and stores rainwater, providing a moist growing environment where microalgae, fungi, lichens and mosses can thrive … A waterproof layer separates the organisms from the inner structural part of the concrete, while an outer layer acts in reverse, allowing rainwater in and preventing it from escaping … The concrete also absorbs carbon dioxide in the atmosphere and acts as an insulating material and a thermal regulator, say the researchers.”

 Journalist Matthew Burgos describes the work of Dutch company Respyre, “… a living city is a healthy city. By creating space for nature — in an otherwise barren environment — and integrating self-sustaining vegetation in an efficient, sustainable, and functional way, we want to bring cities to life. with bio-receptive concrete and moss facades, Respyre empowers cities to breathe … Moss is incredibly well-suited for green facades as moss has rhizoids instead of roots. Rhizoids are nondestructive. they mainly function as an adhesive, leaving the facade in perfect condition, whereas roots are very invasive and demand a lot from the substance they grow in. Our bio-receptive concrete creates a substrate that suits the rhizoids’ wishes perfectly.”

I imagine a city center with canyons of green moss-covered walls keeping the temperatures down and the humidity up. The softer walls could even reduce ambient noise levels, making things more pleasant for pedestrians and others on the streets.

I think the concept of adding more moss puts a new spin on the concept of “going green!”

Additional information:

Emilie Chalcraft , Researchers Develop “Biological Concrete” For Moss-Covered Walls, January 3, 2013, DeZeen

Matthew Burgos, Moss Concrete, designboom, February 15, 2022

US Environmental Protection Agency, Reduce Urban Heat Island Effect, March 23, 2022