For big problems, I'm a big fan of big solutions. After all, the sheer scale of systemic issues all but demands concerted efforts when it comes to fixing them. Even so, we can build in small developments that distribute the burden of change over a wider area. In the case of air pollution, where causes and effects are both diverse and widespread, it makes sense to hit it from both angles. This month saw a noteworthy development for long-tail environmentalism: students at University of California, Riverside have positively tested smog-eating roof tiles. Students at the University's Bourns College of Engineering developed a titanium dioxide coating that, when applied to the roof tiles of an average sized home, "breaks down the same amount of smog-causing nitrogen oxides per year as a car driven 11,000 miles [produces]." Not a small claim.
To put it in context, they calculated that if tiles on one million roofs were coated with their titanium dioxide mixture, 21 tons of nitrogen oxides would be eliminated daily. Particularly impressive if you consider their report that "500 tons of nitrogen oxides are emitted daily in the South Coast Air Quality Management District coverage area, which includes all of Orange County and the urban portions of Los Angeles, Riverside and San Bernardino counties." Nitrogen oxides are produced by burning certain fuels at high temperatures, and when exposed to sunlight and volatile organic compounds they form the cozy city blanket known as smog. Not known for its rejuvenating effects, smog has a growing bad rap sheet and efforts to dock it are vital to urban health.
There are pollution-absorbing or -neutralizing tiles on the market already, and several proposals using titanium dioxide, but few have sufficient data to qualify their claims. Although their work hasn't been peer reviewed yet, the finding is promising. Additionally, the students anticipated that their coating could be applied to existing roofs for as little as $5 per roof. With an adoption cost that low, large scale implementation could be feasible. Impressive enough work that it got an honorable mention in the EPA's recent P3 Awards.
The study compared identical off the shelf roofing tiles coated in different amounts of titanium dioxide. The tiles were placed in an enclosure connected to a source of nitrogen oxides along with a device that reads concentrations of nitrogen oxides. Ultraviolet light was used to simulate sunlight, to activate the titanium dioxide and allow it to break down the nitrogen oxides. The glaring upshot was that the titanium dioxide coated tiles removed between 88 percent and 97 percent of the nitrogen oxides in the chamber. However, in my humble opinion, the exciting part is this: They also found there wasn't much of a difference in nitrogen oxide removal when different amounts of the coating were applied. Surface area, not the amount of coating, is the important factor. The tile with 1/12 the amount of titanium dioxide pulled almost as much from the atmosphere, suggesting that a relatively small amount of the material will be sufficient for effective use.
A cheap retroactive treatment like this looks particularly attractive when compared with the hulking but questionable mega-solutions proposed by architects, artists and insane people for generations. "Smog-killing" concrete-based structures are typically so energy inefficient or high in emissions to create that their green claims come across as unsatisfying lip service. With a low enough adoption cost, a mid-scale effort like roof treatment could be a vital part of a more comprehensive (read: preventive policy-driven) effort. For thematic example, cities faced by drought have had reasonable success by distributing high efficiency adapters for taps and showers. Implementing recycling and green waste programs has been similarly effective at waste reduction.
All of the students involved with the study will be graduating this June, but the program intends to keep the study going, so if you're in a city like LA... keep holding your breath.