Air

Clean air is something we usually take for granted, and yet of course, we can't live without it.

Mexico City, for example, has some of the worst air pollution in the world, yet people continue to live there, in fact in greater numbers than ever, with the current population at over 8.6 million, larger than that of New York City.

And there are other issues in addition to urban smog and other obvious pollution. In fact, even if outside air is relatively clean, interior air in buildings can still be rather hazardous to humans.


The U.S. Environmental Protection Agency has found that certain types of air pollution can be from two to five times higher inside buildings than outside, even in rural areas. The EPA's studies have shown that indoor environments can contain harmful volatile organic compounds (VOCs) due to off-gassing from a wide variety of building materials, furniture and carpeting, electronic equipment, dry-cleaned clothing, cigarette smoke, and even personal hygiene products used by building inhabitants. The presence of these VOCs, especially in combination, seems highly likely to have some deleterious effect on human health, and is probably related to what’s become known as “sick building syndrome.”

But progress toward a solution has been made by two Canadian scientists. Dr. Alan Darlington of the University of Guelph has created the concept of the “biowall.” He has done this by building on the work of another scientist there, Dr. Mike Dixon. Dixon’s specialty is the use of plants within closed systems, such as would be the case in a space ship, a greenhouse on Mars, or beneath the Moon’s surface.

While there are unrelated products also known as biowalls, Darlington’s “living-breathing-wall” inside the Robertson Building in Ontario is a mesh-like structure that contains fans and water-recirculating pipes. Thickly festooned along this interior wall are lush tropical plants, such as bromeliads, ferns, orchids and peace lilies, which provide both natural beauty as well as filtration of the air inside the building. Water is pumped over the plants at the top and then drains down into reservoirs at the bottom, to be recirculated. The flowing water is said to provide a pleasing sound, enjoyed by the building’s occupants. At the same time, fans draw air across the plants and then blow it back into the room.

Even larger than the installation at the Robertson Building is the four-storey, 150 square-meter biowall installed in the atrium of the University of Guelph-Humber Building in Toronto. But both (basically a vertical application of hydroponics) work the same way, removing VOCs as well as carbon dioxide.

Once gasses have been drawn into the plants, bacteria in their root systems break down the volatile organic compounds, thus cleaning the air.


If you’ve ever entered an actual rainforest, you’ve experienced the almost indescribable freshness of the air within. That air often has an amazingly invigorating, almost “living” quality. The biowall is a step toward providing air of that quality in an interior setting.

And it seems that biowall-like structures could easily be built into private homes, for example in bathroom shower areas with skylights above them (perhaps augmented by grow-lights). The requisite plumbing and fans would be easy to add, or perhaps considerable benefit could even be gotten without them, just watering the plants when one showers and relying on already-existing bathroom fans to circulate the air.

At our own home in Florida, we have a secluded outdoor shower area laden with lush plants, and even there, the air has a remarkably fresh quality.


Another concept gaining popularity in urban areas is that of the green roof. Green roofs are flat, urban roofs that have been planted with grasses and other plants. They can provide many benefits, including the provision of wildlife habitat, cooling of the structure below, and retention of rainwater that would otherwise be lost down storm drains to pollute waterways. Instead, the water is absorbed by plants or returned in large part to the atmosphere through evapotranspiration from the plants’ leaves (which can also create a cooling effect). On top of this, green roofs reduce reflection of the sun’s heat into a city’s air, and (like biowalls) absorb carbon dioxide and VOCs.

In addition, when flying over a city covered with green roofs, the effect would be much more pleasing to the eye than just a vista of stark, bare building tops. It could be more like flying over a series of individual gardens.

And food crops can even be grown on city roofs, using hydroponic techniques if the roofs can’t support the weight of actual soil. Another way to keep the weight of soil down is by adding aluminum cans to the soil, increasing the volume of area in which roots can grow.

Using similarly innovative techniques, William McDonough has proposed that an entire city in China use its roofs to grow crops, thus making the top of the city into a huge farm! And Mayor Daley in Chicago has made a major move toward equipping his city with green roofs, with the stated goal of making it the “greenest,” most environmentally-friendly city in the United States, if not the world.

Although perhaps reminiscent of the sod roofs used in early American pioneer days, green roofs are more sophisticated and attractive, and promise to provide myriad benefits in urban and suburban settings.

I know that I, for one, have always disliked the absence of trees and other greenery in many urban environments. However, places like New Orleans and Key West, with their lush balconies and finely landscaped courtyards, have always been appealing to me.

But I also know that many urban residents don’t share my aesthetic viewpoint. Nonetheless, the use of such approaches as the biowall and green roof have much more than just aesthetic advantages, and can benefit anyone living in a city, even those who don’t care about being “Green.”

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