Where Has All The Rubber Gone?

Makarand writes "We all recognize vehicle tailpipe emissions to be a source of pollution. But what happens to the castoff rubber from your tires that have lost tread? No one knew where this rubbber was going until recently. Allison Draper, a professor of environmental chemistry at Bucknell University, is conducting research to end all guess work on this topic and with the hope of finding ways to make tires less polluting. She found for every kilometer a car travels, about 90 milligrams of tread wears off in particles ranging in size 10-75 microns.Toxins in the larger suspended particles leach out when exposed to water and the run off harms plant and animal life. These toxins are still being identified."

Comments

New rubber composition

[Alethes]

I remember reading a while back about a guy that convinced Nike to remove a few of the toxins from their rubber soles so they would cause less problems for the environment. I wonder if the same thing could be done with tires.

Odd, I thought this had been resolved long ago

[MacAndrew]

I remember this question being posed 30 years ago. My rough recollection is that UV light was significant to the decomposition of the "rubber" bits (it's a petrol product) and that they were somehow biodegradable when washed away. It's noteworthy that the stuff doesn't pile up on the side of the road.

A figure I recall is that Americans use up 100 million tires a year.

The particulates causing asthma could be plausible. Another suspected culprit is diesel particulates or DEP. The particles may be more or less benign, but cause an irritation that might contribute the the rise in asthma and other respiratory problems.

Anyway ... what are the chances of a significant reformulation of tire rubber?

Re:Odd, I thought this had been resolved long ago

[antirename]

There has been research for years on using urethane tires to cut wear and rolling friction, but they have a bad habit of expanding from heat. In other words, drive at 60 mph for a few minutes and it comes off the rim. An old professor worked on this for years... although it seemed like his main dissapointment in the failure was that "it would have been really cool to make tires in whatever color you want". Scientists :)

Experimental Design

[Guppy]

It looks like Dr. Draper is taking a very direct method of testing this out -- grind up tires, expose to water, raise test organisms in water. Looks like a very empirical approach.

One thing about the rubber that comes off tires is that it's worn and weathered. Both the surface where the wear is directly, and the particles themselves have had time to oxidize, which is going to change the types of compounds that you'll leach from your samples. More accurate results might be obtained if she took her ground samples, and let them age a bit while exposed to air and sunlight. Some substances would break down or be altered, while other new ones might be formed during this time.

After leaching the particles, you might then pass it through soil samples. Larger particulates will settle out, while some organic substances will bind to clays or be degraded by microbes. The results might be more like what actually ends up in run-off.

If she wanted to take a more reductionist approach, she could obtain the individual substances used in tires, and test them individually against her organisms. Butadiene rubber, Carbon black, Silica (sometimes), Sulfur vulcanizing agents, etc. This ignores any reactions that may occur between the ingredients (probably minimal for some ingredients like carbon black, but extensive for the vulcanizing agents, for example), but gives some hints as to what exactly is causing your problems.

Runaway tires?

[phorm]

How about the effects of "retread" tires on the environment? Here in BC, we have a lot of big trucks going through. Since new tires are expensive, they get continuous retreads (basically old tires with new tread applied). You see a lot of "gators" on the side of the road, in the road, etc where large portions of the retread have simply come loose and spun away.

Granted, retreading a tire is probably nicer on the environment than bringing out a whole new tire, but not when these retreads are laying along roadsides polluting etc.

Not to mention that some of these suckers are quite large. When they come flying off of big-rig towards you, it would be somewhat of a safety hazard?

Re:Runaway tires?

[Anonymous Coward]

What makes you think it is a retread?

Tires ARE manufactured like this. The tread is not an integral part of the tire.

MILLIgrams?

[Gothmolly]

90 mg/km = 1 kg per 11111 km =
1 lb or rubber per 3080 miles?

I have 70,000 mile tires on my car, so does that mean that when they're old, my tires will be 22lbs lighter, EACH?

I find this suspect...

Re:MILLIgrams?

[BandwidthHog]

I myself was wondering if that statistic was per tire or per car, i.e. four tires. If it's per set of four, that would put 70,000 miles of wear at about seven pounds, which I could believe, if forced to.

Interesting. This means that in addition to balding tires give you a bit more dry traction, they now give you slightly better mileage through reduced weight. Science is just racking up reasons for me to put off a new tire purchase.

Re:Also depends on treadwear rating of tire

[antirename]

High performance tires don't "wear" as much as they "age" due to heat changing their chemistry and grip. Go to any roadracing course that is used by motorcycle racers and you will find a) racers selling R compound rubber with two races on it and plenty of tread, but no grip due to heat changing the rubber and b) plenty of street squids wanting to buy it to tell their fellow squids that they have R compound tires on their bike. As long as the wannabe never pushes the tire, he never knows the difference and it wears out in a couple of months anyway (most don't, so everyone wins). Really sticky tires just don't last long, for more than one reason.