Solid Waste & Recycling

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Bringing Down the Roof

Unlike the Brother's Grimm story involving a stranger's ability to spin straw into gold, the potential of tear-off-shingles (TOS) to be converted into a valuable commodity is anything but a fairy tale...


Unlike the Brother’s Grimm story involving a stranger’s ability to spin straw into gold, the potential of tear-off-shingles (TOS) to be converted into a valuable commodity is anything but a fairy tale.

More than one million tonnes of roofing waste goes into Canada’s landfills each year. Studies show, however, that transforming asphalt shingles into a fuel source could virtually eliminate that waste and cut greenhouse gas emissions significantly.

“At present, construction and demolition (C&D) recycling operators consider TOS to have very little worth, valued only for their density and ease of handling,” explains Doug Robinson, consultant for Halifax C&D Recycling.

“The perception that TOS are of low value is conventional wisdom in the waste management business because the components, namely bitumen, have traditionally been a low cost energy source,” continues Robinson.

Convention, however, must sometimes give way to reality.

Economics

As the price of oil dramatically rises, the call for alternates to oil intensifies. Tear off shingles may be part of the answer to this supply vs. demand fuel challenge as potential end-users of TOS realize the energy embodied within shingles.

“TOS fuel potential is boundless,” explains Robinson. “The bitumen content of shingles is typically thirty per cent by weight that of new shingles. In comparison, the bitumen content of the Alberta Tar Sands (the largest deposit of oil in North America, and the largest supplier to the U.S.) is approximately 12 per cent by weight per tonne of sand.”

This means a tonne of TOS has more than twice the bitumen content as the Alberta Oil Sands.

Certain attributes make TOS fuel a very attractive alternative to coal as it will reduce sulphur and mercury emissions.

“Independent tests indicate fibre fuel made from TOS has the same average energy value of coal at 11,400 BTU/lb, but with less than two per cent sulphur and no mercury,” explains Robinson.

Furthermore, estimated reductions in greenhouse gasses will be realized since processing a tonne of shingles into fuel produces one tonne of carbon dioxide, compared to 60 tonnes of carbon dioxide for one tonne of coal.

“High energy users, such as cement kilns, coal-fired generating stations and many other applications where coal is the prime fuel may be part of the equation,” says Robinson.

“Already, the two cement kilns in Quebec are burning tires as alternate fuel but they still need more alternative energy to lessen the impact of the new carbon tax recently imposed by the province. TOS may be the answer.”

Halifax C&D Recycling is currently having great success using a technology that upgrades TOS into two new materials; fuel fibre and asphalt sand. The sand is sold to a local paving company, while the flake — a fibrous material covered in asphalt — goes to Lafarge’s NA cement kiln located in Brookfield, Nova Scotia.

“The bitumen content of the sand averages 18 to 20 per cent of the weight of the sand,” says Robinson. “With the current market value of asphalt bitumen hovering over the $400 per tonne mark, the sand becomes a cost-effective supplement to asphalt pavement for paving contractors.”

Harnessing the potential within TOS means altering the way we handle shingle disposal. This will affect many stakeholders, from homeowners and builders to roofing companies and landfill and recycling operators. Most importantly, we must consider the end users: the energy consumers.

“Potentially, we will be able to offer high volumes of fuel and asphalt supplement while conserving ever diminishing landfill capacity,” explains Robinson.

According to Robinson, up to 90,000 tonnes of carbon dioxide could be cut each year by adding five per cent of shingle sand to hot mix asphalt.

Canadian hot-mix asphalt plants produce about 30 million tonnes of material each year. Substituting just five percent of the virgin material — about 1.5 million tonnes — in the hot mix asphalt would eliminate all roofing scrap generated annually.

Robinson predicts that the end-uses for TOS will continue to expand beyond the current low-profit applications as knowledge of the inherent fuel capabilities of TOS increases.

“However, government regulators need to re-think the definition of TOS from a waste product to a recycled oil commodity, much like they view recycled plastic,” says Robinson.

Debra Wells-Hopey is a freelance writer living in Halifax, Nova Scotia. Contact Debra at gowrite@eastlink.ca


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