Sustainable Pavement Technologies

Sustainable Pavement Technologies (SPT) is a green technology firm specializing in asphalt roofing shingle recycling and other beneficial reuse programs for the road construction and power generation industries. Recycled asphalt shingles are used in the following applications;

• In asphalt pavement to replace virgin asphalt binder

• In power plants and cement kilns as an alternative fuel source to replace coal and fuel oil

SPT currently has processing centers and shingle drop-off locations in the Midwest and Southwest where area roofing contractors can dump their shingles instead of taking them to the landfill. This will allow roofers and home owners to ensure this oil-based product does not end up in our landfills and significantly saves on disposal costs. Please see the Locations section of our website for updated maps of our shingle drop-off sites!

Background on Shingle Recycling

SHINGLE COMPOSITION

Asphalt roofing shingles are made of a felt mat saturated with asphalt, with small rock granules added, and are described as follows:

Asphalt cement: 19 to 36 percent by weight. Asphalt used in shingles is considerably harder than asphalts used in pavement.

• bullet Organic shingles contain 30 to 36 percent asphalt.

• Fiberglass shingles contain 19 to 22 percent asphalt.

Mineral filler/stabilizer (limestone, silica, dolomite, etc.): 8 to 40 percent (90 percent is smaller than .15 mm, 70 percent is smaller than .08 mm.)

Mineral granules (ceramic-coated natural rock, sand-sized): 20 to 38 percent.

Felt backing (mat): 2 to 15 percent. There are two types of mats:

• Organic felt, made with paper (cellulose).

• Fiberglass felt.

WASTE STREAM COMPOSITION

Shingles in the waste stream can be either old or new.

OLD SHINGLES

The majority of waste shingles are tear-offs from re-roof jobs or demolition debris. The load may contain contaminants, such as nails, and wood if the underlying plywood is also replaced. Roofs are replaced roughly every 20 years. Old roofs are often overlaid with new shingles, so some tear-offs contain a 20-year-old layer plus a 40-year-old layer. Twenty to forty years ago, most shingles contained organic mats.

NEW SHINGLES

After most shingles are manufactured, tabs are cut out to shape the shingles for assembly. These tabs contain fresh asphalt. Also discarded are new shingles that did not meet quality standards. Today, most new shingles contain fiberglass mat.

PROCESSING STEPS

To prepare shingles for use in asphalt pavement, the shingles need to be processed according to end use specifications and for state projects according to specific state Department of Transporation specifications. This typically includes removing non-shingle debris and properly sizing the material for each end use application.

GRINDING

Typically grinders are used to size the shingles initially.

SIZING

Depending on the equipment used, primary grinding may yield 2" or 3"-minus size pieces. Secondary grinding may be required to make smaller pieces if needed; for example, aggregate base may require 3/4"-minus, and asphalt pavement may require 1/2"-minus or 1/4"-minus.

GRADING

Depending on the use, the shingles may have to be sieved after grinding, to conform to grading requirements.

ASBESTOS

Asbestos is no longer used in the manufacture of asphalt roofing shingles. The incidence of asbestos-containing shingles in roof tear-offs today is extremely low. The total asbestos content of asphalt shingles manufactured in 1963 is only 0.02 percent; in 1977, it dropped to 0.00016 percent. The average life of a roof is between 15-25 years, so it is unlikely that there will be asbestos in the current shingle waste stream. SPT still has a rigorous asbestos testing protocol which includes testing the shingles using polarized light microscopy before grinding. Any shingles found to contain asbestos are taken to an approved disposal facility.