With about $5 and a few hours of work, the roof on a typical house could start eating smog.
A recent study from the University of California-Riverside found that in a single year, a low-cost tile coating can remove the same amount of nitrogen oxides as a car emits when driving 11,000 miles.
It isn’t the first time someone has plastered building parts with a smog-eating coating, but this might be the cheapest application. In some existing products, like a concrete roof tile that cleans the air, the coating is already built in–so it’s more complicated and expensive to make the switch, and less likely that many people actually will.
“When the titanium dioxide is mixed into the tile, you have to buy the tile whole,” says Jessica Moncayo, one of the students who worked on a team to test the new coating. “The cost to re-roof your house with the tile is about $22,000. That’s kind of hard, especially if you want to target the Los Angeles community like we do. We wanted to pick the same technology, but instead create a coating that you could apply on existing roofs.”
The coating is made from titanium dioxide, which breaks down an ingredient of smog when it’s exposed to sunlight and turns it into a harmless byproduct. When it washes off a roof, it can actually help fertilize plants or a lawn below.
It can also be painted on other surfaces. “One of the new places it could be applied is on rails next to freeways, or anywhere near the emission sources,” says Moncayo. “A lot of emissions are coming from tailpipes near vehicles, so it’s better to put the coating closer to that–especially in places like downtown L.A. where there are fewer rooftops and a lot of cars.”
Though more testing is needed in the real world–the students were only able to test the coating in the lab–the technology might last about five to ten years, the same amount of time as a coat of typical paint. In that time, the coating could gobble up as much as 97% of the nitrogen oxides that pass over it. Because the coating is white, it could also help save energy used for air conditioning by reflecting heat away from buildings.
“We were trying to find an incentive for customers, because it’s hard otherwise without an immediate result,” says Montoya. “That’s why it’s white, so people can save energy costs.”
If implemented at a large scale, the researchers say the technology could make a true difference: A million coated roofs could suck up 21 tons of nitrogen oxides in a single day.