Recently WUWT carried a story about “solar roads” which had a ridiculous premise with a big batch of “feel good” Eco-egineering that is technically and economically implausible. This idea for catalytic reduction of smog looks far more plausible and less expensive.
Students develop titanium dioxide roof tile coating that removes up to 97 percent of smog-causing nitrogen oxides
RIVERSIDE, Calif. (www.ucr.edu) — A team of University of California, Riverside’s Bourns College of Engineering students created a roof tile coating that when applied to an average-sized residential roof breaks down the same amount of smog-causing nitrogen oxides per year [produced by] as a car driven 11,000 miles.
They calculated 21 tons of nitrogen oxides would be eliminated daily if tiles on one million roofs were coated with their titanium dioxide mixture. They also calculated it would cost only about $5 for enough titanium dioxide to coat an average-sized residential roof.
That would have a significant impact in Southern California, where 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.
Last month, the research by the UC Riverside team – Carlos Espinoza, Louis Lancaster, Chun-Yu “Jimmy” Liang, Kelly McCoy, Jessica Moncayo and Edwin Rodriguez – received an honorable mention award for phase two of an Environmental Protection Agency student design competition.
A UC Riverside student team who worked on the project last year received $15,000 as a phase one winner of EPA’s P3 (People, Prosperity and the Planet) competition. That team consisted of William Lichtenberg, Duc Nguyen, Calvin Cao, Vincent Chen and Espinoza (an undergraduate then who is now a graduate student at UC Riverside).
Both teams were advised by David Cocker, a professor of chemical and environmental engineering, and Kawai Tam, a lecturer at the Bourns College of Engineering.
Nitrogen oxides are formed when certain fuels are burned at high temperatures. Nitrogen oxides then react with volatile organic compounds in the presence of sunlight to create smog.
Currently, there are other roofing tiles on the market that help reduce pollution from nitrogen oxides. However, there is little data about claims that they reduce smog.
The students set out to change that. They coated two identical off-the-shelf clay tiles with different amounts of titanium dioxide, a common compound found in everything from paint to food to cosmetics. The tiles were then placed inside a miniature atmospheric chamber that the students built out of wood, Teflon and PVC piping.
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.
They found the titanium dioxide coated tiles removed between 88 percent and 97 percent of the nitrogen oxides. They also found there wasn’t much of a difference in nitrogen oxide removal when different amounts of the coating were applied, despite one having about 12 times as much titanium dioxide coating. There wasn’t much of a difference because surface area, not the amount of coating, is the important factor.
The current team of students, all of whom are set to graduate in June, are hopeful a new team of students will continue with this project and test other variables.
For example, they want to see what happens when they add their titanium dioxide to exterior paint. They are also considering looking at applying the coating to concrete, walls or dividers along freeways. Other questions include how long the coating will last when applied and what impact changing the color of coating, which is currently white, would have.
“They also calculated it would cost only about $5 for enough titanium dioxide to coat an average-sized residential roof.”
Typical mistake of confusing raw material costs with total costs. Hiring a contractor to coat ANYTHING (be it water) on your roof will cost more than 2000$. It’s the same mistake that made nuclear power to be percieved ‘too cheap to meter’ in the 1960s
Nobody around here has tiles on their roof. We use shingles, ceramic or, more often, asphalt.
Since the vast majority of homes and other buildings are coated in paints containing serious amounts of titanium dioxide already, there probably is a strong anti-pollution effect going on already (assuming this paper is correct), and it would be hard to add enough paint to a modern building to increase the effect by more than a few percent.
If you can see the color of the paint, the surface probably isn’t “coated” enough from dirt and mold to reduce the supposed effect.
Of course, there’s always other things we could paint.
I know…
“TITANIUM DIOXIDE FREAKIN’ ROADWAYS!”
TiO2 is used in making paper and plastics in addition to paint. it’s quite a common chemical.
http://en.wikipedia.org/wiki/Titanium_dioxide
TiO2 is already used for NOx reduction in Selective Catalytic Reduction which uses NH3 (often from urea) to convert NOx to N2 and H2O. http://en.wikipedia.org/wiki/Selective_catalytic_reduction
Perhaps they are trying Non-selective catalytic reduction, such as is found in automotive 3-way catalysts. (NSCR in industrial settings uses ammonia).
The NOx in the air has to be on the surface and likely in a certain temp range and/or, as it looks in the picture, with lots of UV light, if they are not just heating the tile. You have to have a pretty good air exchange at the surface to get all this to happen.
arthur4563 says:
June 5, 2014 at 4:34 am
“Nobody around here has tiles on their roof. We use shingles, ceramic or, more often, asphalt”
Perhaps the government should mandate everyone have tile roofs, seems the green thing to do.
I would also hope that hurricane prone states get a waiver as heavy roof tiles can be very destructive when torn off and flying around in 100 mph winds.
Let’s see, on topic it is worth remembering that nitrogen oxides, produced naturally by lightning, are the original source of nitrates in soil, and nitrogen in the soil is the chemical raw material used by plants to make protein, and that we are protein, not cellulose. So this isn’t an idea for the rural masses, this is strictly a big-city idea as only in places like Los Angeles are automotive N+O compounds overt pollution instead of fertilizer. And yes, Titanium Dioxide has long been the basis for very white paint. This is a good thing. Titanium is extremely abundant (as is oxygen), and as far as I know is not toxic. Indeed, I recall that its oxide is extremely stable.
The more interesting question is what it does to e.g. SO_2. Sulphates in the air are not fertilizer, they are the source of acid rain in the bad sense (unbalanced by being fertilizer). Of course, they are also aerosols, and hence supposedly lead to increased cooling. It is also interesting to compare a TiO_2 tile or painted rooftop to the pollution-reduction capacity of one single tree:
http://urbanforestrynetwork.org/benefits/air%20quality.htm
I don’t think people realize that a significant fraction of the increased carbon dioxide in the air comes not from human activity, but from the fact that we’ve cut down the world’s forests and turned them into farmland, houses, tables, charcoal, etc. This has created a huge alteration in the natural carbon cycle, as growing trees are a very significant carbon sink. To quote from the article above:
I don’t know how seriously to take this, but if taken at face value then the cheapest way to achieve global carbon neutrality isn’t to spend a gazillion dollars on renewable energy, it is for every American family to fund the planting of 20 trees. Since planting a tree costs nothing at all — trees kindly provide us with any number of seeds and nuts for the cost of picking them up off of the ground — the real cost of this is land. But even if this is exaggerated, there is little doubt that deforestation is a major anthropogenic cause of the increase in CO_2 worldwide, and that reforestation is a few million times more efficient than solar cells or windmills as a means to combat increased CO_2 than trying to starve civilization of energy (and has numerous side benefits as well, as trees do indeed eliminate a lot of actual toxic pollution on an annual basis).
Finally, when I saw the article and Anthony’s lead in comments, I thought that he was going to suggest that we paint all the roadways with TiO_2, thereby increasing the mean albedo of what is (believe it or not, I worked this out with a pencil) a nontrivial fraction of the surface area of the US, especially around major urban centers, to substantially reduce the UHI effect. Of course, painted on roadways and rooftops, it would have an even larger effect. There is an enormous difference between the surface temperature above thick grass or trees (which use some of the incident sunlight to make sugars, evaporates water with some of it to maintain transpiration), black asphalt (which gets so hot one cannot walk on it in the summer daytimes), comparatively white concrete (which one can barely walk on) and the white lines drawn on the asphalt. I learned as a kid that when I walked in bare feet to the Skaneateles Lake swimming aspect in summer (which is not at all “hot” in upstate New York:-) that to cross the roads you either walked on the white lines marking the crossing or you burned the hell out of your feet.
If we (as a society) simply added enough TiO_2 to concrete mix to cause it to come out bright white we would reduce the solar heating of all upward facing surfaces made with it by (I’m estimating) 40 to 50C compared to asphalt, 25 to 30C compared to ordinary concrete. Similar cooling would be obtained if all asphalt roof shingles were white. By “cooling”, I also mean “reduction in air conditioning bills”. I don’t know if people have any idea what the true cost of putting that cute (but dark) forest green shingle all over their roof is. Amortized over a 20 year lifetime, I’ll bet that it triples their cost relative to a bright white shingle in increased AC costs, at least in the south where I live. Ditto dark cars with black upholstery (I recently rode in one of those and its air conditioner couldn’t even keep up with the heat generated by the sun on the front dashboard as we drove — I quietly cooked).
Covering your roof with solar cells can be an (unsubsidized) winner in terms of cost-benefit, especially in parts of the country where electricity is comparatively expensive. Obama and the EPA have just taken measures to ensure that this is basically “everywhere” in a future coming to you soon, so expect the long-awaited boom in solarization to start (ready or not) this year. A great time to invest in the technology, and you can buy the stock from Al Gore and the many, many people who have been quietly buying it up already while pushing for precisely this legislation to force it to have value. However, it takes over a decade to win the amortization of cost war, and quite a long time to win the energy war as well, as one has to pay back the energy cost of mining, smelting, making the cells, transporting them, and installing them before showing an energy “profit”. A bright white roof, OTOH, is an instant winner. Pigment is cheap, both dollar cheap and energy cheap. If there were some way of turning black asphalt (cheaply) white that would be a huge winner. Planting more trees is cheapest of all, and trees are themselves often economically valuable as a renewable resource for wood, non-commercial fuel, and food or just habitat for other things we find valuable.
The thing is, I (like many skeptics) am sympathetic to a lot of the “Green” agenda. Reducing actual toxic pollution in our highly anthropogenically toxic environment is a super idea — one cannot eat fish from the Great Lakes more than once a month because of lead, mercury and PCBs dumped into the “great sewer” of the midwest industrial belt, and it will take a century or so before it “flushes” enough that one can. Giant bare asphalt parking lots lit at night with mercury vapor lamps that will inevitably release some of their mercury into the environment and that burn energy utterly pointlessly all night long while heating to broiling temperatures every sunny day are as offensive to my sight as to anyone’s. There is so much that we could do here — legislate a requirement that massive parking lots retain enough greenway to support both trees and watershed, paint or pigment the pavement of those parking lots white, and turn off the lights at night (or at least, but the lights on a motion detector so that they are on only on demand when humans are there to see or use the light). That alone would reduce the UHI effect of those parking lots on local temperatures, while shading the cars and sequestering all of that carbon and detoxifying all that pollution. The point is, it isn’t really about the carbon. Mankind’s largest anthropogenic effect on the climate might well not be the burning of carbon at all.
rgb
I’ve read the literature and researched photocatalysts for 2 decades. It’s a passion of mine. Some info
” They are also considering looking at applying the coating to concrete, walls or dividers along freeways”
Ten years ago I submitted a proposal to the DC Council of Governments to do this. Didn’t go anywhere. I was focused on dividers and sound walls b/c of the wear on road surfaces AND because TiO2 can have the property of superhydrophilicity, which I didn’t think would do well for traction.
I will also point out that researchers at Lamar University published results of auto exhaust breakdown after coating asphalt w/ TiO2 (c. 2007).
TiO2 paint in paint is actually encapsulated in SiO2 in order to eliminate it’s catalytic effects. It is my hunch that TiO2 breakdown of the binder is why paint peeled so readily in the early 20th C, and why companies switched to Pb as a pigment.
Even is it works as claimed it has no chance as that setup also catalyzes hydrocarbons to CO2 and H2O so the EPA will prevent its use.
You can also coat your shingles with Titanium dioxide, or acyclovir. 😛
So, you can reactivate the catalyst by peeing on the roof. :P:P:P
PhilCP says:
June 5, 2014 at 4:20 am
“They also calculated it would cost only about $5 for enough titanium dioxide to coat an average-sized residential roof.”
Typical mistake of confusing raw material costs with total costs. Hiring a contractor to coat ANYTHING (be it water) on your roof will cost more than 2000$. It’s the same mistake that made nuclear power to be percieved ‘too cheap to meter’ in the 1960s
_______________________
Nope. Bubba would see his opportunity to have plenty of work and undercut the other guys. The first Mom and Pop that gritched to the local news “Gotcha” team about paying $2000 for a contractor who arrived, completed the spray job and left within 1 hour would smarten up the customer base.
Good bait. They should hook a green grant in fairly short order.
Beethoven
Thanks for that Nature link. Another quote from that article that could easily be shifted to the climate debate:
“The BICEP2 incident has also revealed a truth about inflationary theory. The common view is that it is a highly predictive theory. If that was the case and the detection of gravitational waves was the ‘smoking gun’ proof of inflation, one would think that non-detection means that the theory fails. Such is the nature of normal science. Yet some proponents of inflation who celebrated the BICEP2 announcement already insist that the theory is equally valid whether or not gravitational waves are detected. How is this possible?
The answer given by proponents is alarming: the inflationary paradigm is so flexible that it is immune to experimental and observational tests. “
Ironically, titanium dioxide mineral is called rutile! Time to install new ruftiles.
More white roofs would also reduce UHI. If I recall Obama’s first head of Dept. of Energy, Dr. Chu, wanted us to paint roofs and roads white to offset AGW.
I do question how long long the roof coating could stay effective as an air cleaaner or as a reflector. If it requires an annual recoating, I doubt if it will be practical. But Tio2 is an interesting compound that is getting attention:
An interesting side note is the ISS uses a TiO2 coated air filtration system utilizing UV lights to clean the air on the space station.
http://spinoff.nasa.gov/ISSspin.html
TiO2 coated surfaces are also used on earth to purify air and kill microbes:
http://www.nature.com/srep/2014/140219/srep04134/full/srep04134.html
TiO2 is well-known for use as a delustering agent in fibers, paints and other materials. It also is a great UV blocker. So, it is not new to use TiO2 in paints and coatings (eg., sun screens, until recently). Most of the basic chemistry is already known. One question is how to efficiently get the NOx in the air to contact the panels. You won’t be working with a closed, pumped system.
This is an intriguing idea, but what about the rest of the nation that does not use tiles for roofing? Can it be built into traditional shingles? What about metal roofs? Wolfman’s also got a great point, how well will it work in the actual atmosphere? The bench scale testing is done, now they need something to simulate more realistic conditions, like the same test rig in a barn filled with NOx, with a couple of box fans that cycle on and off during the “day” and “night”.
i seem to recall reading somewhere, likely here, that having large numbers of white roofs results in less rainfall, which is the last thing we need here in #Failifornia…
if it will still w*rk if it isn’t white, they may be on to something.
Lighten up, folks, these are just kids! Universities SHOULD be giving their students the opportunities to work on creative solutions to real-world problems (and yes, oxides of nitrogen do constitute a real health threat, as they contribute to atmospheric ozone concentrations proven to contribute to mortality and morbidity).
Not everything that every student team accomplishes will change the world, but that isn’t the point. I congratulate them for their creativity and hard work on this project.
Are your collective memories that short? TiO2 struck with sunlight is self cleaning due to ozone formation when activated with UV. So, if all of your roof receives sunlight, it should stay quite clean and moss free. I thought this was already covered here on WUWT, but I seem to be mistaken.
http://www.greenoptimistic.com/2013/06/14/self-cleaning-compound-increases-the-levels-of-air-pollution-instead-of-removing-it/
https://www.peakpureair.com/how-tio2-uv-photocatalytic-oxidation-pco-works
rgb:
In theory, your suggestions seem plausible (white roof/concrete vs dark asphalt), but there is one place on earth that it is put into practice and it does not work nearly as well as one would think – the Middle East. Ask any serviceman/woman who has served in AOR and they will tell you: Simply put – everything over there is white or lightly colored and it is still HOT AS HADES IN LATE AUGUST over there.
On paper is one thing, in practice is something else entirely.
Here is another use of TiO2 that claims that the photocatalyst converts the NOx into nitrate.
Dang, I just need some of these blocks set at grade level scattered about the yard for free fertilizer.
http://en.wikipedia.org/wiki/Noxer
“up to 97 percent …”
Ah, it’s that number again!
Does it have some mystical significance in the field of climastrology?
If this idea gains traction, it will be BITTERLY fought by the “Solar Industrial Complex,” who have other ideas for what people should be putting on their roofs.
une toiture végétale –
http://midex.ca/fr/pourquoi-toits-verts/
grass and clay –
http://en.wikipedia.org/wiki/Green_roof
http://www.chaumiers.com/toit-de-chaume.htm
http://en.wikipedia.org/wiki/Thatching
Bonsoir
This is old stuff, PPG makes self-cleaning glass using the same photocatalytic TiO nanoparticle process and ultraviolet (UV) light, the dirt literaly oxidises and washes off in the next rain. If I can get sqeeking clean windows by garden hose and it burns off some nitrogen oxides along the way I’m a happy camper.
One or more of the US automakers back in the 1970’s proposed to the EPA using a heat-activated coating on vehicle radiators to destroy air pollutants, probably ozone, in southern California. The EPA refused to give the automakers any emission reduction credits, so the idea was dropped.