[moses lawn (OP)]

Thousands of roads, millions of cars, trucks, lorries, buses etc., all with tyres, all of which are wearing down all the time.

So, many tons of rubber being worn off all those tyres every day, but where does it all go to?

Why aren't we knee deep in black rubbery stuff?

[neilep]

That's a good question Moses Lawn !!..I thought the tyre fairies come and clean the roads each night :-)..I suppose the same can be said for the tread of your shoes too....my guess is that it eventually becomes a component of roadside dust and eventually gets washed away by the rain and wind into virtually every corner of our environment....and that's what I think....after all...where else can it go ?

Hey !!..just found this :
http://www.rma.org/newsroom/release.cfm?ID=241...it's a study studying potential environmental and health impacts on tire materials and tire roadway particles !

Ahh !!..this is interesting too....I think it's the original page that my now replaced link linked to !...if you know what I mean ! http://www.goodyear.com/corporate/about/environment/03-ehs/hottopics.html  (edit July 2008)

[Exodus]

This is really interesting... am just moving it to the general science section

[chris]

Mmm, interesting, but the research was carried out by Goodyear themselves, so one must always raise the spectre of 'conflict of interest'. did you come across any independent analyses of the contribution of tyre-wear to environmental contamination Neil ?

Great topic though. Nice one.

C

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[neilep]

Hi Chris, Fraid not....I felt the same that an idependent study would suffice but all I found was Goodyear one...sorry.

'Men are the same as women...just inside out !'

[tweener]

I remember reading somewhere that the dust from tires is a major contributor to particulate air pollution over cities.  I don't remember where that came from.

----
John - The Eternal Pessimist.

[neilep]

The amount of research done by commercial enterprises, such as the petro-chemical industries, Electricity and tyre/rubber and many others etc is phenomenal.....though often their results (dependent on the industry) may be interpreted as biased, it goes without saying that their contribution to scientific study and knowledge must be enormous......

sorry, was just touching on a point Chris made by the study of tyre wear by Goodyear. I don't think for a minute that Chris was being critical, but the comment did make me think of the significant benefit made by commercial enterprises (as well as bad ones of course)...



'Men are the same as women...just inside out !'

[Ylide]

Incidentally, tire waste is one of the products that can be successfully recycled out of the environment with thermal depolymerization.  They can be broken down into elemental carbon (graphite), sulfuric acid, and natural gases.  The energy required to do this on each tire is less than what would be yielded in the chemical energy of the natural gas from each tire.  I really can't figure out why this technology is not taking off faster.  



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[roberth]

Recycling old tyres is fairly common. The process involves chopping the tyres into small bits, cryogenically freezing the rubber, smashing the crap out of it when frozen, screening it to remove the steel and running it through a sieve to get standard size rubber pellets. Our company uses these pellets in the manufacture of flexible cement based adhesives. Councils use it in parks, under the structures that kids play on, so when they fall, the concrete is rubberised and doesn't hurt. It's a lot more useful as rubber than broken down into it's elements. The main roads departments are the largest users of recycled rubber.

[Andy Thompson]

A lot ends up bound to road aggregates, where it gets washed down drains, into the sewers, adn around the wate water treatment works. There, road grit, probably containing a lot of rubber particles, is seperated into skips, and probably either used for construction or goes to landfill.

[Gareth Gilbert]

I've just had a new set of tyres. The originals lasted 30 000 km so we can calculate an average thickness of rubber worn off starting from a new tread depth of 7 mm: 7mm over 30 000 km gives 0.2 millionths of a mm per metre of road. Carbon atoms (the main components in a tyre) are about the same siz in diameter, so it looks as though individual carbon atoms are being removed from a tyre as it wears!

[rglater]

Tyre wear: tyre and particle composition

newbielink:http://vergina.eng.auth.gr/mech0/lat/PM10/Tyre%20wear-tyre%20and%20particle%20composition.htm [nonactive]

What Happens to the Rubber That Wears Off a Car's Tires? Bucknell University Chemistry Professor Investigates Environmental, Health Impacts of Tire Wear Particles

newbielink:http://www.collegenews.org/x1939.xml [nonactive]

Gah an latha,

[chris]

quote:Originally posted by Gareth Gilbert
so it looks as though individual carbon atoms are being removed from a tyre as it wears!

You obviously realise this Gareth, but just in case anyone is not clear about this, this result is an average. In reality the tyre will wear in fits and starts with larger chunks of material, containing hundreds or thousands of atoms, detaching periodically.

We actually answered a version of this question on a recent edition of the naked scientists radio show and podcast. Here's the link if you'd like to listen to it:

Naked Scientists Science Radio Show March 26th 2006

But if you'd just like to read, here's the answer I gave:

"I've just been doing a quick calculation. If a tyre lasts for about five years, I reckon it comes out at about 10 000 tonnes a year of rubber in the UK. Tyres are actually really bad polluters because they don't only contain rubber but also a lot of heavy metals too. That's why when people say let's just burn old tyres, it's really bad because the toxins go up into the atmosphere and drop out into the soil that animals eat. If we focus on the US, 300 million people live there. Let's assume that they all have two cars per family of four. A car has four wheels, which means that in the US at any given time there are probably roughly 600 million tyres in use in any given year. Let's assume that the tread on a rubber tyre is 10 centimetres wide, the circumference of the wheel is 3 metres, and the thickness of the tread is about a centimetre. That means that the volume of rubber on a wheel and rubbing out is about 3 litres. If there are 600 million tyres and you times that by 3 litres, and then convert that to metres cubed, that's a staggering 2 million metres cubed of rubber every single year just in America. The density of rubber is 1200 kilograms per metre cubed. That means that there are 2 billion kilograms of rubber in tyres in the US. If you assume that they last for four years, that means that roughly two billion kilos gets lost or worn out every four years. That's a staggering amount."

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[Monox D. I-Fly]

So... Since condoms are made of rubber, when one uses them, did the rubber particles get left in their sex partner? I've never had sex, so I have no one else to ask...

[evan_au]

condoms are made of rubber

Modern condoms are single-use, and are discarded before any appreciable wear or tear occurs.
- Condoms still need to be disposed of (usually ending up in landfill)...
- They are used in a considerably less abrasive environment than car tires, which means they don't need so many heavy metals in their construction; they could be made more ecologically friendly than car tires.