Waste Management Update #2: Asphalt Roofing Shingles

by NAHB Research Center

The asphalt shingle is the most common type of roofing material used in both new home construction and reroofing, accounting for over 60% of the residential roofing market. Asphalt roofs generally last from 12 to 20 years and then require replacement or recovering. Reroofing generates an estimated 6.8 million tons of waste asphalt shingles each year--equivalent to nearly 3% of municipal solid waste. Wastes which shingle reroofing generates include

• Asphalt shingles (90+% of the waste stream)
• Miscellaneous packaging, fasteners, & roof trim

ALTERNATIVES TO DISPOSAL

Some attempts have been made to recycle shingles into new shingles, but problems persist in reprocessing shingles to conform to feedstock requirements. Recycling involves the use of heavy equipment (tailored for processing shingles and minimizing dust) to grind or shred shingle waste to a size useful in paving materials

• Parking lots or temporary roadways
• Aggregate base course
• Hot mix asphalt wear course
• Pothole/road patch material
• Granular base stabilization layer
• Expansion joints
• Moisture barrier under base course (unground)

Many players are involved in the diversion of asphalt shingles from landfills

• Roofers generate tear-off waste
• Manufacturers generate manufacturing scrap
• Haulers transport waste to the recycler
• Recyclers process the waste, creating a value-added product
• Governments sanction the use(s) of recycled shingles
• Pavers use the waste in paving applications

ISSUES

Roofing waste lends itself to recycling because

• It is usually generated separately from other wastes
• Recycling and paving technologies currently exist

The primary limiting factors of recycling include

• Department of Transportation (DOT) paving specifications
• DOT requirements for field tests
• Roofers' interest in simple, easy disposal
• Logistics and economics of collection
• Capital expense of setting up a recycling operation
• Marketing of the recycled product

Asbestos
Asbestos was formerly an acceptable ingredient in residential three-tab shingles, but asbestos-content shingles were not used in all areas of the U.S.. Grinding asbestos-containing roofing material (ACRM) generates dust containing friable asbestos, making all present and future uses of the ground shingles hazardous. To prevent this, recyclers must examine and may need to test incoming roofing materials to keep ACRM from being processed. Tests cost from $15 to $25 per sample and can take up to 24 hours for results.

Paving
Shingle waste's asphalt content replaces some of the virgin asphalt used in paving materials (shingles' granular content may replace some of the aggregate components).

Manufacturer Scrap vs Reroof Waste. Because asphalt shingles are manufactured with varying amounts of asphalt, fiberglass, cellulose, and granular materials, the composition of waste shingles varies from roof to roof. Reroof waste may also contain contamination (metals, paper, or misc. trash). Manufacturing scrap is uniform in composition and condition and comes from one source, resulting in a pure recycled material. These qualities and the lack of contamination allow paving manufacturers to better predict the impact that manufacturing scrap will have on the performance of paving materials.

Performance. Each state's DOT writes a pavement specification designed for road durability based on local climatic conditions. The specification prescribes the composition of paving materials, approved additives, and field applications. Recycled shingles' beneficial effect on performance must be demonstrated to the local DOT's satisfaction (in field tests) in order to be incorporated into the specification. DOTs are also concerned about the long-term recyclability of roads and the stiffening of asphalt with time (stiffness negatively affects pavement durability in colder climates).

STEPS TO TAKE NOW

• Ask your state DOT about shingle-content paving.
• Call your local (city or county) recycling office to locate businesses that will recycle shingles.

Many of these issues are being investigated under a pilot waste management project being conducted by the Research Center in Maryland. Results of this project will be available in Fall 1997.

Copyright © 1996 NAHB Research Center, Inc. This work is used with the permission of the copyright owner for publication on the Smart Growth Network web site. Any copies of this work shall include this copyright notice.