Public Works: Building Infrastructure That Cleans the Air
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Public Works: Building Infrastructure That Cleans the Air

Barcelona is building a traffic bridge out of pollution-neutralizing concrete. Chicago has paved a road with it. Could Toronto adopt the trend?

Public Works looks at public space, urban design, and city-building innovations from around the world, and considers what Toronto might learn from them.

Rendering courtesy of BCQ Architects.

The City of Barcelona has commissioned a local architecture firm to redesign the Sarajevo Bridge, a drab concrete span over a drab concrete roadway.

The bridge will include pedestrian lanes and benches, and will be partially enclosed by a framework of hanging plants. It will be lit by a combination of low-energy LED lights and a photo-luminescent pavement.

But the real prize of this thing is its basic building material, photocatalytic concrete. The principal of photocatylitics is that ultraviolet light naturally breaks down dirt, both natural and synthetic. It’s that old adage about sunlight being the best disinfectant. Photocatalytic concrete is used with titanium dioxide, which helps accelerate the natural UV-breakdown process, turning the pollution into carbon dioxide, and oxygen and substances that actually belong in the atmosphere.

The actual process has to do with semiconductors and electrons and other things that you may or may not care to read about. (At any rate, the Concrete Society of the United Kingdom does a better job of explaining it.)

An air-cleaning bridge makes for a neat news story and a sci-fi-ish novelty that environmentalists can blog about. But the important point is that Barcelona has taken a piece of infrastructure that exists solely to accommodate car culture, and re-invented it to partially offset the effects of car pollution.

Some North American cities have adopted the same philosophy—and the same building materials. Back in 2008, Minneapolis, Minnesota, inaugurated a highway bridge over the Mississippi River that was decorated by photocatalytic cement sculptures at each end.

In 2012, the City of Chicago upped the ante, unveiling the “Greenest Street in America”–3.2 kilometres of roadways paved with photocatalytic concrete, built primarily from locally sourced materials and dotted with wind and solar-powered pedestrian crossing lights.

Here in Toronto, environmentally friendly development is gathering steam. The Toronto and Region Conservation Authority has released a guide to “climate change mitigation” aimed at municipalities. “Climate change management needs to become systemic in city planning,” reads the TRCA literature.

Toronto continues to grow, evolve, and change. The waterfront is being developed. Developers are building condos across the city. Even already-bustling communities are being reworked to create a better, more modern city—just look at the Eglinton Connects project.

As this city moves forward, it’s worth considering not only the potential of green building materials, but the philosophy behind them—that even the seemingly environmentally unfriendly facets of a city can pull their weight in the campaign to build a greener society.

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