Here’s something that, if it works, would be great to use to line the streets of smoggy cities. The University of Twente has possibly figured out a way to get paving stones to scrub the air, turning nitrogen oxide into a harmless nitrate that can wash away with rain.

The secret is in the sauce, so to speak – titanium dioxide is mixed with the concrete which catalyzes chemical reactions with light exposure. So when sun hits the bricks, the nitrogen oxide (mainly from car exhaust) is turned into nitrates. And then when the rain comes down, the nitrates are washed away with the dust. The university claims the nitrates are harmless, so we wouldn’t run the risk of having just another form of toxin like we do with nitrates from heavy fertilization.

Testing will be going on this year with some preliminary results by next year that will show the effectiveness of the paving stones. Should the stones pull the trick, this could be a pretty cool breakthrough in green construction materials. Especially if cleaner methods of concrete manufacturing is used, since concrete is pretty CO2 intensive to create. Perhaps we’ll even see them in more green housing communities.

Via cnet, photo via University of Twente

Comments (11)

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Nitrates?
written by Clinch , August 11, 2008

If it's nitrate (NO3-), then it's just as toxic if comes from bricks, or fertiliser, there are not different types of nitrate, it's one molecule, regardless of the source.

There are problems with Nitrate
written by youme , August 11, 2008

Please don't believe that all you hear is truly green.

Orwell will be pleased
written by jim , August 11, 2008

Surely there is a trick of language going on here. Nitrates aren't toxic. They cause environmental damage due eutrophication, but that doesn't mean it is toxic.

...
written by Clinch , August 11, 2008

No, they're still toxic.

...
written by Matt , August 11, 2008

Nitrate rain = algae bloom, doesn't it?

lifespan?
written by Mumia , August 12, 2008

If the stones reacts with nitrogen oxide and sunlight, wont that mean they degrade a lot faster than ordinary stones, and hence needs to be replaced a lot quicker, with a lot more polution as a result?
Besides, isnt this like putting a band aid on the guy that has had his leg bitten off by a tiger, while the tiger is busy eating the other leg?
Get those nonpolutant cars to the public please, no more band aids, treat the illness not the symptoms.

...
written by Bob Wallace , August 12, 2008

We're most likely to solve the energy/climate change problem via a million little solutions, a death of a thousand cuts, rather than one great big silver bullet.

Celebrate every little 'fix'. Don't put stuff down simply because it isn't big.

@lifespan
written by Clinch , August 12, 2008

The brick doesn't get used up in the reaction, it acts as a catalyst (the titanium keeps being used to help the reaction, but isn't used up itself).

Also, people aren't putting this down because it's a 'little fix' they're putting it down because it's not a fix at all, as it produces a toxic chemical.

I also think that with increasingly efficient, and less polluting vehicles, and catalytic converters, the problem doesn't seem to be high enough to warrant the extra pollution from production of these bricks.

Excellant Environmental Blogs
written by Sandy , August 14, 2008

Wonderful environmental concerned posts on SU and on Blog! Bravo, and keep up the good work.
Sandy

nitrates
written by chris brandow , August 17, 2008

This is an interesting case of perhaps lesser of two evils. the nitrous oxides are definitely bad, and the nitrates are less toxic. But they definitely are a nutrient that leads to greater algae growth. This is probably useful in certain areas like Los Angeles where the air quality is a much bigger deal than algae blooms, but probably not such a good solution for larger cities along the Mississippi. However, again, it would be interesting to see how much nitrate would be produced by this compared to the tremendous amount of nitrate leached from over-fertilized fields.

eutrophication
written by Marcel , August 19, 2008

Nitrate is indeed a nutrient. It might cause the grass next to the road to grow quicker or ditches filling up with algae and other aquatic plants more rapidly. On the other side, it will hopefully help in cleaning up pollution in the sky, which causes respitory problems.

To understand why certain research is done in a country, look into the problems there; over here in the Netherlands, NOx is becoming an ever increasing problem, caused by very high amounts of traffic. Stating it's not a problem by just replacing all polluters is something that is set in motion by imposing restrictions on NEW cars. With the long lifetime of current vehicles, it will take time before that actually solves the problem. Till then, inventions like these help mitigate the problem.

Oh and by the way, grass can be cut you know.

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