A team of American students has developed a titanium dioxide coating for roof tiles which has been proved to eliminate the nitrogen oxides that cause smog.

A Roof Tile Coating that Can Help Eliminate Smog

Vehicle traffic is one of the chief causes of air pollution and Spanish researchers have come up with an infrared detection system which identifies excess pollutants on motorways in real time and can help the authorities to take the necessary ad hoc action. However, roads are not the only places where major sources of air pollution can be reduced. A team of students from the Bourns College of Engineering at the University of California (UC), Riverside has now developed a type of coating for roof tiles which breaks down the nitrogen oxides that are the basis of smog.

Treated tiles helping to combat pollution

Nitrogen oxides are formed when certain fuels are burned at high temperatures. These oxides then react with volatile organic compounds in the presence of sunlight to create smog. The solution developed by the students is a titanium dioxide coating for roof tiles on residential buildings, which acts as a catalyst to help break down nitrogen oxides before they collect in quantity in the air. To test their approach, the students coated normal clay tiles with various thicknesses of the titanium dioxide mixture and placed them in a mini atmosphere chamber they had built for their experiments. The chamber was connected to a source of nitrogen oxides and a device that reads concentrations of nitrogen oxides. They used ultraviolet light to simulate sunlight, which activates the titanium dioxide and allows it to break down the nitrogen oxides. The team found the titanium dioxide coated tiles removed between 88% and 97% of the nitrogen oxides. They also discovered that there was not much variance in nitrogen oxide removal when different amounts of the coating were applied. They concluded that the surface area covered, not the thickness of the coating, is the most important factor.

Further applications

Currently, there are other roofing tiles on the market that help to reduce pollution from nitrogen oxides. However, there little data has as yet been collected to substantiate the manufacturers’ claims that they reduce smog. The team has calculated that 21 tons of nitrogen oxides would be eliminated daily if tiles on one million roofs were coated with their titanium dioxide mixture. They also worked out that it would cost only about $5 for enough titanium dioxide to coat the roof of an average-sized residential building. The UC Riverside team’s research received an honourable mention during phase two of a US Environmental Protection Agency student design competition. The researchers are now thinking about other applications of this approach, such as applying the coating to concrete, walls, or dividers along motorways, and also about the impact of using colours other than the current white.  

By Eliane HONG