Tyres hang around

December 11, 2006 at 11:35 pm 1 comment

There are only so many kids’ swings or white garden swans that you can build from discarded tyres. Worn out tyre disposal is a world-wide problem, so you are not alone with those secondhand tyres you’ve stored in the garage for a rainy day, which you will probably never use. What to do with them? Where do they go when you load them on the trailer for a trip to the tip, and find out that the tip won’t take them. That’s why they figure so prominently in the news after every “Clean Up Australia Day”. Don’t add to the problem!

Australia discards around 12 million, plus or minus a million, every year. U.S.A. probably 70-100 million. Outside L.A., there is a mountain of tyres one mile square, and last seen over 200 metres high. An absolute haven for snakes, rats, vermin, and mosquitoes. The owner of the site charges tyre services which flock to his site, for the privilege of dumping them there. He is convinced that one day, some entrepreneur will find a use for them. Meanwhile, it’s a huge fire risk. The bureaucrats of the European Common Market have just awakened to the fact that they have an even bigger problem. One enterprising truckie in N.S.W. established his own dump in the bush on the Central Coast, and was sprung when that caught fire, which took months to extinguish at his expense.

Recently, dumping of a poisonous European petrochemical refinery by-product in Niger in Africa, highlighted the trade in by-products that no-one wants. Cardboard and paper, and all the recyclable plastics, find a ready trade, mostly to China, where they are sorted and recycled. Unfortunately, there is no major source of disposal for old tyres, and the problem grows apace.

Another promising disposal tried was as a marine reef, offshore, to break up wave action, and provide a harbour, or lessen erosion. Great efforts were made to lock the tyres together with concrete blocks, chains, anchors, and anything heavy. However, the power of the sea cannot be denied. After a few years, the reefs broke up, and tyres ad infinitum were dumped on the beach, to be picked up again. Geelong in Victoria, Australia was one such trial, another you might like to read is about a reef established with the best intentions in Florida.
It’s the shape of tyres that causes one of the problems. They contain a high volume for their weight. The other reason is that the chemicals used in rubber to prevent it perishing in sunlight and weather, also are very persistent, and prevent marine organisms from attaching themselves to the rubber.
I well remember being asked to identify a tyre dredged up from Darwin harbour in 1976, as a curiosity. It was still inflated, and attached to an artillery piece. The romance of the story fell in a heap when the serial number disclosed that the tyre had been made two months after the war ended. The tyres and the gun had made it to Darwin just in time to be dumped in the harbour, having no further use. The point of the story is that the serial number was still quite readable 30 years later, no decomposition having occurred.

Let’s look at the possibilities.
Because of their shape, tyres are difficult to dispose in land fill. They don’t rot, and trap air inside the casing, so that it is difficult to consolidate the ground. After a few years, they tend to work their way to the top again. When split into two halves circumferentially, and the two halves laid on top of each other, this objection is removed. However, it requires a special machine which has to be capable of cutting through two layers of steel under the tread. You can fit a lot more tyres on the truck for the trip to the tip, though.

A better approach is to cut the tyre up into chips of rubber if they are to be used for landfill. This is slow, and takes a lot of power in a heavy, robust machine. Once chipped however, other processes can be applied to recover the steel, to chop it up even finer for use as playground surfaces, bowling green surfaces, in road asphalt, and the like. It makes asphalt more flexible, less likely to crack in snow country. But the outtake volume is just not there.

It’s a terrific fuel. Rubber tyres burn beautifully, hot, and smokily, which can be corrected by furnace design. But rubber is cured using sulphur. There is a huge push to clean up power station and diesel engine emissions of sulphur, by cleaning up their fuel. Oxides of sulphur emitted from their exhausts combine with elements in the atmosphere, to cause “acid rain”. So that’s out. Experiments have been done on distilling the tyres in retorts to recover the oil. The economics aren’t there either, particularly if you can’t heat the retort with old tyres- a Catch 22 situation.

Tyres can be retreaded if they pass stringent inspections to ensure their reliability. It is entirely dictated by economics. To retread a tyre for a second tread life is not unusual. Consider however, that the modern steel belted radial has already done twice the tread life of a bias ply tyre, when retreading of bias was commonplace. Retread it, and you expect four times the casing life of the old bias ply tyre, with 100% reliability. You are ‘stretching the envelope”. Realistically all you are doing is delaying the day when eventually the casing has to be disposed of, though you have reduced the demand for a new tyre.

So your tyre dealer will ask you for an “Environment Fee” to take your old tyres off your hands. A truck calls round to his tyre service, sorts the retreadable casings” from the scrap, and drives away, bound for a municipal tip that still takes tyres. Their number is reducing too. You could ask which tip he uses, if you want to dispose of them yourself.

So arise all you entrepreneurs, and put your thinking caps on. It’s not only Houston that has a problem of monumental proportions.

Entry filed under: Environment. Tags: , , , , , , , , , , .

Tyre Bursts Original Equipment

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