Approximately 11 million tons of asphalt shingles are collected in landfills every year. What many people don’t realize is that asphalt is 100% recyclable. Recycling the asphalt-cement in shingles benefits asphalt producers by reducing AC costs and improving the quality of their product, as well as reduces the nation’s dependency on foreign sources of oil and clears up valuable landfill space for products that can’t be recycled and reused. Asphalt shingles can be recycled into a variety of products, including hot mix asphalt, cold patch, dust control on rural roads, temporary roads and driveways, aggregate road base, new shingles and fuel. With the rising cost of petroleum, the economic benefit of using recycled asphalt shingles (RAS) is also increasing. Using RAS reduces overall costs on projects in several industries, such as the overall cost of paving a road or roofing a house.
Hot-mix asphalt (HMA) is currently the largest market for RAS. Using recycled asphalt reduces the demand for virgin asphalt cement and aggregate, which economically benefits HMA producers. Cutbacks from shingle factories can be ground and added during the HMA process, and the ceramics in shingles serves as a source of aggregate in the mix, reducing the demand for mined aggregate. The addition of RAS has been proven to improve rutting and cracking resistance in asphalt pavement because the added mineral fillers and organic fibers help reinforce the matrix.
Various other industries see the benefit of use of RAS rather than other materials for certain applications. The fibers from the felts and fiberglass found in shingles give cold patches made from RAS a longer life compared to those made of other materials. Recycled shingles that are ground into gravel and used to cover unpaved roads have been proven to minimize dust, reduce the amount of gravel lost into side ditches and reduce vehicle noise on these roads. These roads also tend to have a longer life and require less maintenance; a study on Iowa roads showed little or no dust produces and high performance with minimal maintenance requirements for the duration of the two-year study. Also, the use of RAS to create new roofing shingles led to significant energy savings, and a U.S. Department of Energy study showed that the addition of up to 20% recycled shingles did not affect the production of new shingles.
Simplified, the groundwork of recycled shingle processing consists of a few basic steps. First the scrap shingles are collected at a processing plant. Next they are sent through a grinder to be taken down to be taken down to a size of ½” or smaller. From the grinder they are sent to a trommel screen that sifts out the pieces larger than ½”. The pieces larger than ½” are either sent back through the grinder to be ground again, or are collected as a base course blend. This process is repeated in a cycle until all material not being passed on as base course blend has been ground down to smaller than ½”. Those pieces small enough to pass through the screen are sent to an asphalt plant to be further processed through an HMA and prepared for reuse.
Grinders use abrasion and compression to pulverize materials to a reduced size, using a series of wheels, drums and plates to process the material. Material is passed through a wide feed hopper, falling into the grinding chamber. Often, grinders use a hammermill in the grinding chamber to process the shingles. In this case, the grinding chamber contains a rotating hammer rotor with swinging hammers that crush the shingles and drive them through a screen, thus using impact grinding to reduce the material into smaller scraps. Some grinders come equipped with a grapple for easy loading, if not some form of loader is often used in the shingle recycling process to transfer the shingles from the fill pile into the grinder. Grinders are available in high or low speed models. Grinders such as the Proto Grind Model 1200 Horizontal Grinder, the Rotochopper EC-156 Horizontal Grinder (Electric), the CMI Maxigrind Model 460G Horizontal Grinder, the Morbark Waste Recycler and the Diamond Z Model 140BL-11Tub Grinder with Grapple/ Loader are all great models for use in asphalt shingle recycling.
Trommel screens consist of a rotating cylinder maintained in a frame and are used for sifting work. As the screened cylinder rotates, it separates material by size, letting the smaller pieces pass through the openings while keeping the larger pieces inside. The pieces that are too big to fit through the screen are passed back to the grinder. This is repeated over and over in a loop until all of the material has been shredded down to a small enough size to fit through the trommel screen. Worldwide Recycling Equipment Sales, LLC manufactures new trommel screens in a variety of sizes, such as the Tuffman Model 722 Stationary Trommel Screen, Tuffman Model 618 Stationary Trommel Screen and the Tuffman Model 830 Stationary Trommel Screen.
As RAS rates increase, sales of these key pieces of equipment parallely increase. And, with a more than 148% increase in the amount of recycled shingles from 2009 to 2010, these numbers are only expected to grow.