THREE mines in Limpopo province are undertaking trials aimed at proving the feasibility of replacing wooden underground cocopan rail sleepers with products made from recycled plastic. The trials have been going on for the last four months, and a senior employee at the firm supplying the new rail sleepers says preliminary results have been encouraging.

The mines do not wish to be identified at this stage.

If the new sleepers pass muster, they will offer the South African mining industry significant benefits, says Mark Gibson, manager of Timber Plastics’ plastic-recycling and fabrication factory in Alberton, on Gauteng’s East Rand.

Currently, the company fabricates recycled-plastic dustbins, manhole covers, fire-hydrant covers, drains, duck-boards for ablution blocks, and outdoor benches at the Alberton plant and at others in several towns and cities throughout the country.

According to Gibson, at one of the mines where the trials are being carried out, 30 recycled-plastic sleepers were used on a section of an underground rail next to 30 wooden sleepers.

While the results have yet to be confirmed officially, Gibson says the wooden cocopan sleepers are starting to show signs of wear. The plastic sleepers’ greater ability to maintain their shape under the weight of laden cocopans and other underground mining vehicles is one of the reasons why they are being considered as possible replacements for wooden sleepers imported from Australia.

They also don’t crack or splinter and the fact that they do not absorb water – which is abundant in most underground mining environments – and rot would make them preferable to wooden sleepers.

They burn less easily than timber, and when they do, the only products they release are water vapour and carbon dioxide, both of which are not hazardous.

Wood also produces carbon monoxide – a hazardous gas – when it burns, according to Gibson and Ian Barnard, the director of a Johannesburg-based waste-plastic-collection company which is one of Timber Plastics’ several suppliers in the city.

“The recycled-plastic sleepers do not sustain combustion; they stop burning once they are removed from a flame or whatever would have caused them to burn,” says Gibson.

Another advantage the new sleepers will offer is that, if they break, Timber Plastics – or any recycler with co-extrusion machines – will buy them for reprocessing.

This is not the case with their wooden counterparts, which are discarded once they bend or break.

The wooden sleepers, imported from Australia, which has more hardwood resources than South Africa, cost 10% to 15% less than plastic ones. But Gibson points out that the longer service life of the recycled-plastic cocopan sleepers and the other advantages they offer more than compensate for their initial higher cost.

And the fact that they can be sold back for reprocessing further makes them a good proposition.

Gibson is confident that, should the trials succeed and many mines switch to the new rail sleepers, Timber Plastics will be prepared for the demand. It is estimated that an average-sized mine will require between 50 000 and 100 000 rail sleepers a year.

The company’s Alberton plant currently produces 70 t of recycled plastic a month, but this can be increased to 140 t within months.

“One can also say that there are environmental benefits to be derived: based on the current rate of production we are preventing 70 t of plastic waste from going to landfill sites every month and going up to 140 t a month will obviously mean that the savings will increase,” he says.

The rail sleepers are not the only recycled-plastic products that Timber Plastics is looking to supply to the mining industry.

The company has made ventilation doors which are now being tested.

It has also made limited quantities of blasting barricades that are also to be tested. Its existing range of products, including outdoor tables and benches, drains, manhole and fire-hydrant covers and dustbins, are particularly popular with municipalities.

This is because, unlike products made of steel, cast iron or timber, they cannot be stolen for resale to scrap-metal dealers or for use as firewood and do not require maintenance.