Dutch Town Lays Air-Purifying Concrete

eldavojohn writes "In an effort to combat air pollution, a Dutch town has paved some of its streets with air-purifying concrete. It contains a titanium dioxide-based additive that utilizes sunlight to turn car exhaust into harmless nitrates. It was shown to do this in a lab and now the scientists are interested in just how much this will affect the air quality around the road. They will sample the air quality by a normal road and by this newly paved one."

Comments

Offset?

[Recovering Hater]

Because the purifying concrete offsets the pollution incurred from mining the titanium to create the concrete? Am I wrong in thinking I knew an old lady who swallowed a fly? Someone weigh in on this please. Thanks :P

Re:Offset?

[Anonymous Coward]

This one is obviously about enhancing the air in the city. It is not supposed to solve any large scale problems with the climate. Didn't RTFA.

Re:Offset?

[hardburn]

It might. If it works well enough, it would mean we could either remove catalytic converters from cars (which would increase engine efficiency), or promote the use of small diesels (which can be more fuel efficient but release a lot more NOx), and end up with a net win for smog pollution.

In other words, it doesn't directly do anything greenhouse gases, but it does allow us to produce less greenhouse gases by using techniques that produce more nitrates.

Re:Offset?

[rjhubs]

I supposed it could work because the cost of getting titanium is a one time cost, but the effects of the concrete will continue working over time.

Re:Offset?

[Born2bwire]

It would depend on whether or not the titanium dioxide is acting as a catalyst or component of the reaction.

Re:Offset?

[FireStormZ]

The Titanium is not consumed in this process (merely a catalyst) so it might very well be worth it in the long run..

Re:Offset?

[baldass_newbie]

You should have. They're only paving one side of the street with it. This way they can test the air quality on either side of the street and see if there's any difference.
It's an experiment.
Couldn't see anyone doing 'testing' in a town in the US without two very big teams of lawyers being involved.
Yeah innovation!

Re:Offset?

[mrchaotica]

Actually, there's a recurring cost for the concrete as well: it doesn't last forever, you know! It lasts longer than asphalt concrete, but it'll still need to be repaved after a few decades.

(At least, it doesn't last forever the way we use it -- if we built like the Romans did, it'd last forever but cost a heck of a lot more.)

Re:Offset?

[MillionthMonkey]

If it works well enough, it would mean we could either remove catalytic converters from cars (which would increase engine efficiency), or promote the use of small diesels (which can be more fuel efficient but release a lot more NOx), and end up with a net win for smog pollution.

An exhaust-eating road surface is never going to be as efficient as a guy just chasing your car down the street with a big vacuum cleaner hose. I think we're keeping our catalytic converters.

Re:Offset?

[Anonymous Coward]

How, exactly, is removing the catalytic converter (which acts on the engine's exhaust just before it is expelled to the atmosphere) supposed to help improve engine efficiency? Do you realize what you just said is the equivalent of claiming that a new computer monitor will give you better CPU performance?

Because it's a flow restriction and the engine has to work to pump through it. In fact, particulate filters and catalytic converters and mufflers on new US diesel trucks harm the efficiency so much that it can do as much as 4 mpg damage.

Re:Offset?

[Anpheus]

The catalytic converter isn't as efficient as a straight pipe. While not legal, cutouts that push exhaust straight outside the engine and bypass the exhaust system do improve horsepower.

It's more like bumping up the speed of your front side bus on your CPU. If you have a slower FSB, you might not ever notice it if you aren't racing your ca... CPU. But when you need that speed, it sure would be nice to remove the FSB limitation.

That said, the amount of good that catalytic converters do means we should probably keep them, as they aren't a huge drain on the power of a vehicle.

Re:Offset?

[KGIII]

Al? He's putting on his wizard hat and robe. He'll be unavailable for a while.

Re:Offset?

[lukas84]

Bonus points for using an IT analogy in a car discussion ;)

Re:Offset?

[e4g4]

How, exactly, is removing the catalytic converter (which acts on the engine's exhaust just before it is expelled to the atmosphere) supposed to help improve engine efficiency?

The same way removing your muffler does - both the muffler and the catalytic converter restrict the flow of exhaust in the car (thereby restricting the intake, and subsequently reducing the amount of power the car can generate). NASCAR teams remove the mufflers and catalytic converters from cars - adding about 50HP to the car in the process.

Re:Offset?

[Bruiser80]

Titanium Dioxide is not a rare compound, just like Aluminum Dioxide isn't. Pure Aluminum or Titanium are rare.

The original Crown Jewels contained Aluminum because it was a precious metal at the time. A chemical process was developed by Reynold around the 19th/20th century to convert a lot of Aluminum Dioxide into pure Aluminum using a small amount of pure Aluminum.

Re:Offset?

[infolib]

the pollution incurred from mining the titanium

This is not titanium, it's titanium dioxide which can be mined from the ground in some places. Wikipedia says that "The relatively high market value of titanium is mainly due to its processing" from oxide. Besides that, it's only needed in the surface, no need to fill the whole concret slab, just the layer that'll wear.

Re:Offset?

[howdoesth]

It's more like bumping up the speed of your front side bus on your CPU. If you have a slower FSB, you might not ever notice it if you aren't racing your ca... CPU. But when you need that speed, it sure would be nice to remove the FSB limitation.

Did you just use a computer analogy to explain a car problem?

Re:Offset?

[dgatwood]

Aha! The foot is on the other shoe now!

Wait... what?

:-D

Re:Offset?

[DigiShaman]

While not legal, cutouts that push exhaust straight outside the engine and bypass the exhaust system do improve horsepower.

Not necessarily.

While you will get more torque at the low-end of the RPM range, you might actually be losing overall HP. By having a proper diameter and length of pipe, you can take advantage of the "exhaust savaging" effect.

BTW, my 99 Miata is properly tuned with the right exhaust system.

Re:Offset?

[WebCowboy]

Am I wrong in thinking I knew an old lady who swallowed a fly? Someone weigh in on this please.

No you're quite right, but not quite for the same reason. Concrete and asphalt already used in the roads are the result of intensive mining, drilling and refining processes already, and titanium can be recoverer/reused, so I'd venture to say that though there would be an added environmental impact to include this "air scrubber" additive that it isn't the biggest factor offseting the benefits to air quality.

I'd say a more immediate concern is that this doesn't reduce pollution--it only converts it into anouther type of pollution. Smog-causing Nitrous oxides are certainly bad for our health, but nitrates are far from "harmless". I'd like to know what is done with the nitrates. Can they be recovered and used in a more controlled way (to fertilise crops and what not) or are they just left to be absorbed by the environment (dissolved in runoff, etc)?

Though proper amounts of nitrates are natural and beneficial in ecosystems, excess nitrates in the environment can destroy wetlands and other bodies of water by causing excess algae growth. Nitrates are also bad for animal life, from fish and amphibians to livestock. Nitrates can infiltrate well-basede drinking water supplies as well, creating health problems in people ranging from thyroid problems and vitamin deficiencies to low birth weights.

If there is some way to contain the nitrates as well as enjoy less smog I'd say it is promising, but we still have to work on more efficiently using fuels and not driving personal vehicles as much when there isn't a need to.

Re:Offset?

[paanta]

Government agencies like the DOT does testing all the time. Ever pass a sign on the highway saying you're going to be on experimental pavement for the next 500'?

Re:Offset?

[DerekLyons]

The Titanium is not consumed in this process (merely a catalyst) so it might very well be worth it in the long run..

Assuming the catalyst isn't poisoned by reaction byproducts, or removed by weathering, or sealed under oil etc., or otherwise rendered inactive by environmental effects.

Re:Offset?

[Amouth]

no but i do see signs every day that read "DOT road sign test in progress" - it is there everyday.. for about 4 years now... wonder if i should give them acall and see how the test is going

Re:Offset?

[hardburn]

From Wiki:

These three reactions occur most efficiently when the catalytic converter receives exhaust from an engine running slightly above the stoichiometric point. This is between 14.8 and 14.9 parts air to 1 part fuel, by weight, for gasoline (the ratio for LPG, natural gas and ethanol fuels is slightly different, requiring modified fuel system settings when using those fuels). When there is more oxygen than required, then the system is said to be running lean, and the system is in oxidizing condition. In that case, the converter's two oxidizing reactions (oxidation of CO and hydrocarbons) are favoured, at the expense of the reducing reaction. When there is excessive fuel, then the engine is running rich. The reduction of NOx is favoured, at the expense of CO and HC oxidation. If an engine could be operated with infinitesimally small oscillations[citation needed] about the stoichiometric point for the fuel used, it is theoretically possible to reach 100% conversion efficiencies.

Re:Offset?

[Oktober Sunset]

My asplode just headed.

Re:Offset?

[today]

Just because you pass static emissions tests does not mean your car would pass a full-dyno emission test like they do when the car is under development. The bi-annual test usually only tests the car at a couple of load points, and they assume if it passes those, it is in working condition. You car should not pass a California inspection because they are supposed to check that the CAT actually exists (unless you've simply cored it out or welded a CAT shell around the exhaust pipe to fake it).

My guess since you are tuned for performance is that you are emitting a lot more HC and CO than you would be if you had a CAT installed.

Re:Offset?

[MrKaos]

They're only paving one side of the street with it. This way they can test the air quality on either side of the street and see if there's any difference.

Now we know why the chicken crossed the road!

bad-duum-tish!!!

TFA interesting but light on details

[dedazo]

All passive filters I know require replacement because they get clogged, or the active elements eventually decay. Beyond making jokes about swapping the church bricks five years from now, TFA was a bit light on the details. Does anyone know how does this works, from a chemical perspective?

Re:TFA interesting but light on details

[Rob T Firefly]

I'm also a bit curious about the "harmless nitrates" that will be washed into the ground every time it rains.

Re:TFA interesting but light on details

[Anonymous Coward]

I would imagine that active elements would decay, and that in a number of years, the concrete wouldn't do anything.

But by then, the road would need to be repaved anyways, so that's not really a problem. As long as it remains chemically active for a longer timespan than the life of the road, we're good.

Re:TFA interesting but light on details

[Andy Dodd]

http://en.wikipedia.org/wiki/Photocatalysis
http://en.wikipedia.org/wiki/Titanium_dioxide

TiO2 can catalyze a wide variety of chemical reactions in the presence of ultraviolet light (such as sunlight).

Re:TFA interesting but light on details

[gnuman99]

Nitrate is also known as a fertilizer.

Maybe that will cause people to think twice before,

    1. laying down fertilizer on their lawn, and shipping cut grass to landfills - leaving grass where it is provides the new grass with its own fertilizer.

    2. writing that nitrates can be worse than NOx (NO, NO2 and others)

NO3 is completely harmless compared to the more volatile cousins NOx that come out of tail pipes.

http://en.wikipedia.org/wiki/NOx

Nitrates?

[ArcherB]

Nitrates? Aren't those bad in their own right? I'm thinking along the lines of fertilizer run-off and the affect it has on algae in oceans. Could this solution create worse problems?

Re:Nitrates?

[jascha.cohen]

As i recall from my "environmental studies" class, it's not that nitrates are bad in-and-of-themselves, it's that when they accumulate in an area they can unbalance the system and create problems. Wikipedia has a decent article/overview on the topic. http://en.wikipedia.org/wiki/Nitrogen_cycle

Re:Nitrates?

[AKAImBatman]

Plants need Nitrates to grow. (Nitrates == Nitrogen based chemicals.) So it should actually be positive for the soil rather than negative. I stress *should* because without knowing the exact chemical composition, it's hard to understand if there are any hidden problems with this technique.

One thing I am worried about, though, is the color of these sidewalks. If they're using titanium dioxide, shouldn't they be a nice brown color? (Think: Coffee, cola, and other brown liquids.) I don't know about anyone else, but a brown sidewalk or street is not my idea of "attractive". (I presume the "green" bricks used in this trial have been painted or stained with an even more powerful pigment.) Of course, given the natural color of titanium dioxide, perhaps this technique is intended for use with blacktop rather than concrete as suggested by the article? In which case the brown would be unnoticeable. That would also jive with the replacement time for these roadways as any passive chemical solution is going to become less effective after a few years of use.

It would be nice if the article had more of these details.

Re:Nitrates?

[bcattwoo]

"One thing I am worried about, though, is the color of these sidewalks. If they're using titanium dioxide, shouldn't they be a nice brown color?"

Actually titanium dioxide is quite white. It is used as pigment for white base paint.

Re:Nitrates?

[hey!]

Anything is harmful in the wrong place and in the wrong concentrations. Nitrates are, for example harmful to fish in high concentrations.

Most systems have processes that are limited by the supply of some resource. Ocean ecosystems are nitrogen limited, whereas fresh water systems tend to be phosphorous limited. Thus if the nitrates are washed off into fresh water, they'll cause relatively little immediate damage unless the concentrations are high enough to be toxic. However, if that nitrate is carried downstream to the ocean, the plume of nitrogen rich water entering the ocean can cause blooms of organisms that use up so much oxygen that fin fish suffocate. This happens where the Mississippi enters the gulf.

So, how and where something like this is used makes a difference. If you imagine all the US cities along the Mississippi and its tributaries using it, and if there is a mechanism by which the nitrates make it into the rivers, then this could make the situation in the Gulf much worse. If you use it in a coastal city and only the runoff from that city affects the local ocean, the amount of nitrogen entering the ocean might or might not have any measurable effect.

Re:Nitrates?

[edittard]

The nitrates can't run off into the oceans, because Holland is below sea level.

Re:Nitrates?

[Hal_Porter]

Nitrates? Aren't those bad in their own right? I'm thinking along the lines of fertilizer run-off and the affect it has on algae in oceans. Could this solution create worse problems?

Well they make plants grow and that cuts down on the CO2.

Re:Nitrates?

[bryce4president]

I knew somebody would say this... Its not the nitrates that do the harm, its the phosphates... Just a couple weeks ago this was reinforced... Source

Re:Nitrates?

[clone53421]

Of
  course
  nitrates
  are
  harmless!

Re:Nitrates?

[JohnsonJohnson]

a) Not all of Holland is below sea level, 75% of it is above sea level.

b) Nitrates can still pollute the ground water then diffuse into the ocean and rivers

Re:Nitrates?

[TheLink]

The recent conclusion of a 37 year experiment is it's phosphorus not nitrogen that's the problem:

http://www.canada.com/victoriatimescolonist/news/story.html?id=381d4ce5-89a2-4901-864e-34239419bf67

Schindler's latest series of long-term experiments shows that nitrogen removal completely fails to control blue-green algae blooms. He proved this by manipulating nitrogen and phosphorus levels on Lake 227 for 37 years. Nitrogen control, he found, only encouraged algae blooms.

How green?

[Smivs]

This sounds like a great idea if it works, but surely producing concrete is a far from 'green' process. I wonder how long the concrete has to be in place to neutralise the polluting effect of manufacturing it in the first place.

Re:How green?

[ArcherB]

This sounds like a great idea if it works, but surely producing concrete is a far from 'green' process. I wonder how long the concrete has to be in place to neutralise the polluting effect of manufacturing it in the first place.

But we are producing concrete anyway, so we'll still be ahead as long as this process does not produce more pollution than the pollution from standard concrete + whatever it absorbs.

Re:How green?

[Blakey Rat]

What do you suggest paving the road with? Grass? Good intentions?

Re:How green?

[MightyYar]

Everyone knows that hubris is the best paving material, duh.

Re:How green?

[meldex]

"What do you suggest paving the road with? Grass? Good intentions?"

Well it worked for the road to hell, and I am told that road handles a lot of traffic.

Exact location

[oever]

The road is here according to a Dutch source.

The results are in

[Anonymous Coward]

The scientists driving around to check their air sampling monitors negates any positive effect produced by the concrete.

harmless nitrates ?

[cinnamon colbert]

not to mention all the side products that are produced, msot of which i am willing to bet havenot even been identified, much less studied

J Environ Qual. 2008 Feb 11;37(2):291-5. Print 2008 Mar-Apr.Click here to read Links
        When does nitrate become a risk for humans?
        Powlson DS, Addiscott TM, Benjamin N, Cassman KG, de Kok TM, van Grinsven H, L'Hirondel JL, Avery AA, van Kessel C.

        Soil Science Dep, Rothamsted Research, Harpenden, Herts, UK.

        Is nitrate harmful to humans? Are the current limits for nitrate concentration in drinking water justified by science? There is substantial disagreement among scientists over the interpretation of evidence on the issue. There are two main health issues: the linkage between nitrate and (i) infant methaemoglobinaemia, also known as blue baby syndrome, and (ii) cancers of the digestive tract. The evidence for nitrate as a cause of these serious diseases remains controversial. On one hand there is evidence that shows there is no clear association between nitrate in drinking water and the two main health issues with which it has been linked, and there is even evidence emerging of a possible benefit of nitrate in cardiovascular health. There is also evidence of nitrate intake giving protection against infections such as gastroenteritis. Some scientists suggest that there is sufficient evidence for increasing the permitted concentration of nitrate in drinking water without increasing risks to human health. However, subgroups within a population may be more susceptible than others to the adverse health effects of nitrate. Moreover, individuals with increased rates of endogenous formation of carcinogenic N-nitroso compounds are likely to be susceptible to the development of cancers in the digestive system. Given the lack of consensus, there is an urgent need for a comprehensive, independent study to determine whether the current nitrate limit for drinking water is scientifically justified or whether it could safely

Two problems

[snarfies]

1) From TFA: "'With one rain shower everything is washed clean,' the institution said in a statement." Ah, but exactly WHAT is washed to WHERE, eh? Are we just trading off air pollution for water pollution?

2) How durable is this new substance? How much pollution can the road suck up before it wears out? Will it need to be resurfaced and/or replaced every year? Two years?

This isn't that new

[Devon Dan]

This stuff isn't that new. It definately has been sold for quite a while under the name TX Active [ http://www.italcementigroup.com/ENG/Media+and+Communication/News/Corporate+events/20060228.htm ]. They used it to make the Air France head quarters at Charles de Gaulle Airport a few years back. http://www.physorg.com/news67012896.html

Wow, cool idea!

[bill_kress]

Maybe we could do even better.

Hmm, since we're being green anyway, lets eliminate some of the cars--then perhaps we could make the concrete softer to walk on.

We could use some other color but grey--yuck. Maybe green to represent the fact that it purifies the air.

Being softer, it would be nice if it had some kind of self-patching mechanism...

As long as it's going to be self-patching, let's get really sci-fi and have it create itself using some kind of a system involving materials from underneath itself in some kind of a synthesis process.

Damn, I'm thinking way too far ahead--our science will never get to the point where it can do this stuff. Guess I'll have to be happy with air-purifying concrete.

Meh...

[Thelasko]

Chicago is putting in water purifying concrete.

Hong Kong Polytechnic

[quanminoan]

I did some research for school over in Hong Kong for a few months and worked with the Hong Kong Polytechnic University Civil Engineering Dep. They used titanium dioxide coatings on bricks and highway noise barriers - actually in use in Hong Kong. They also have attached titanium dioxide nanoparticles to textiles to make filtering clothing:

http://www.polyu.edu.hk/cpa/polyu/hotnews/details_et.php?year=all&news_id=255

http://www1.polyu.edu.hk/hotnews/details_e.php?year=all&news_id=964

It's great to see it catching on...

Don't worry, though. It's completely harmless.

[clone53421]

Harmless...

In freshwater or estuarine systems close to land, nitrate can reach high levels that can potentially cause the death of fish. While nitrate is much less toxic than ammonia or nitrite, levels over 30 ppm of nitrate can inhibit growth, impair the immune system and cause stress in some aquatic species.[citation needed] However, in light of inherent problems with past protocols on acute nitrate toxicity experiments, the extent of nitrate toxicity has been the subject of recent debate.

In most cases of excess nitrate concentrations in aquatic systems, the primary source is surface runoff from agricultural or landscaped areas which have received excess nitrate fertilizer. These levels of nitrate can also lead to algae blooms, and when nutrients become limiting (such as potassium, phosphate or nitrate) then eutrophication can occur. As well as leading to water anoxia, these blooms may cause other changes to ecosystem function, favouring some groups of organisms over others. Consequently, as nitrates form a component of total dissolved solids, they are widely used as an indicator of water quality.

What could possibly go wrong, though? It's not like roadways are "surfaces" that might "runoff" into storm sewers or waterways.

air treatment

[FudRucker]

why not get some crop dusters and fit them to release a fine powder of this air cleaning agent at high altitude above cities that have smog & air pollution problems?

what will it do to ground water and lakes & rivers? maybe clean them too?

Re:Human Problems?

[MightyYar]

Even if the nitrates DO wash into the local drinking water and there is a demonstrably bad effect, it still might be a good idea; the health effects of breathing smog might still be worse.

Re:Offset may be ideal

[sm62704]

I doubt this takes the asbestos from brakes out of the air though

They haven't used asbestos in brake linings for a long time.

Nitrates not so harmless! But it won't work anyway

[GPS Pilot]

the additive binds the nitrogen oxide particles emitted by car exhausts and turns them into harmless nitrates. "With one rain shower everything is washed clean," the institution said

Hmm... the New York Times says nitrates are "a dangerous and increasingly widespread pollutant... reaching dangerous levels in groundwater".

It seems environmentalists hold wildly diverging opinions on this.

If the NYT is correct, it's fortunate that this "air purifying concrete" is not likely to be very effective. You see, only a small percentage of the NOx molecules are going to come in contact with the road surface (which makes them eligible for conversion to nitrates). The titanium dioxide in the concrete is not able to reach out and grab NOx molecules floating one meter or even one millimeter above the road. I predict the air quality measurements will show very little difference, and the media will never report on this idea again.

For the system to be effective...

[SamP2]

Nitrates don't need to be harmless, nor there needs to be zero side effects. All that's needed is that the combined damage produced by any side effects must be less than the damage produced by the excess carbon dioxide in lieu of said concrete.

Funny how any time there is a proposed innovation to solve a problem, there are always nitpickers who point out side effects without considering their proportion compared to the original problem being solved. A solution either offers a net benefit, or it doesn't.

Re:Human Problems?

[AshtangiMan]

1. Pave road with this stuff.
2. Drive diesel cars on roads.
3. Nitrates -> algae blooms in marshes just off road sids.
4. Harvest algae and press to make bio-diesel.
5. Profit.

Wouldn't it make more sense too...

[Dex5791]

Put this titanium dioxide-based additive in the exhaust systems?

Re:Dumb comments about nitrates

[avandesande]

These nitrogen oxides will eventually end up as nitrates anyway, the TIO catalysts just speed this up. Or would you rather that people and wildlife breath them into their lungs first?

Stupid.

old news.

[nimbius]

this has been around since 2002. westminster and japan had it first. its called a noxer block http://en.wikipedia.org/wiki/Noxer_block

Re:Eutrophication

[Gat0r30y]

I thought we discussed this - Phosphorus is the limiting agent in algal blooms.

old news

[Goldsmith]

In 1972 it was discovered that titanium dioxide is a strong oxidizer when exposed to light. The following years saw this applied to paints used in hospitals, coatings on windows and building concrete.

This is old technology which has been in use in Japan for many years. Yes, it does work.

Re:Rendering

[xerxesVII]

Rendering them... what exactly?

Or did you mean to suggest that buildings we can't see don't get rendered even though they exist?

Re:Interesting...

[orclevegam]

Seems to be rather widespread usage already according to this wikipedia article.