Shingle Recycling

Polk County implements an innovative program to recycle asphalt shingles

Construction and demolition debris represents a substantial fraction of the waste disposed of in Florida, typically comprising about 9 million tons per year. Recent estimates indicate about 7% of the total C&D debris generated in Florida consists of asphalt shingles—the quantity generated from year to year can vary (sometimes substantially) based on the amount of building activity and impacts from major storm events such as hurricanes. The majority of asphalt shingle waste generated consists of materials removed from roofs (referred to as tear-offs), and this material has been identified as a highly underused component from a recycling standpoint in Florida, despite the fact that many states in the U.S. have successfully recycled asphalt shingles for years. A common recycling end use for asphalt shingles is integration into hot mix asphalt (HMA). This practice can decrease the amount of liquid asphalt needed by a HMA facility (representing a cost savings, depending on the price of liquid asphalt) while increasing the amount of recycled materials and extending the life of disposal facilities. A potential benefit to roofing contractors that generate tear-off shingle waste is a reduction in waste management costs. Many programs that successfully recycle asphalt shingles in the U.S. incentivize the practice by offering lower tipping fees.

Anecdotal evidence suggests that post-manufacturer asphalt shingles (which represent about 10% to 20% of the total asphalt roofing waste generated) are recycled at some HMA facilities in Florida for use in private paving jobs, but the recycling of tear-off asphalt shingles is rarely practiced. Discussions with local regulatory agencies and waste handling facilities suggests the major hurdles to wide-scale implementation of the recycling of tear-off asphalt shingles in Florida relate to concerns with the potential presence of asbestos-containing materials in roofing loads, economics (e.g., cost to permit, stockpile and process tear-off shingles), as well as the lack of a specification to allow processed tear-off shingles on most county and state road projects. This study aimed to investigate some of these issues further and develop a plan that can be used as a guide by solid waste management facilities, roofing contractors and HMA facilities to identify and address the technical and economic considerations associated with asphalt shingles recycling. The Polk County Waste Resource Management Division, Jones Edmunds & Associates, Inc. and Innovative Waste Consulting Services, LLC were awarded an Innovative Recycling Grant from the Florida Department of Environmental Protection to carry out the study in 2009 and 2010.

A detailed plan of execution was developed to recycle asphalt shingles at the Polk County North Central Landfill (PCNCLF) located in Winter Haven, Fla. The execution plan included (1) visiting a previously-existing asphalt shingles recycling operation to understand the benefits and challenges faced by the facility, (2) identifying a stockpiling area on site based on expected material volumes, (3) creating a specification to require the haulers to bring only clean loads (i.e., exclusively shingles), (4) creating an economic incentive (a waived tipping fee) for haulers that complied with the specification, (5) developing a protocol to sample accepted loads for asbestos, (6) identifying equipment to process the stockpiled asphalt shingles, (7) identifying an end user that would use the processed materials, and (8) selecting target areas at the PCNCLF to be paved so the performance of the asphalt shingle-amended HMA could be assessed over time.

Approximately 100 tons of clean asphalt shingles were delivered to the stockpile area at the PCNCLF (located in an area of intermediate cover at one of the facility’s active, lined landfill cells) during the nine month stockpiling period. This material quantity was lower than expected, and the low tonnage was mostly attributed to the low level of on-going re-roofing activity in Polk County, lack of contractor participation despite the incentives that were extended, and the inability of some contractors to meet incoming material quality specifications on smaller re-roofing jobs.

The project execution plan, which was submitted to and approved by the Florida Department of Environmental Protection’s Southwest District Solid Waste office, called for the collection of one asphalt shingle sample per 25 tons received for asbestos analysis. However, more frequent sampling (one sample per 6 tons) was conducted to gather additional research data and add a factor of safety to the project. None of the 16 samples collected during the project resulted in a detection of asbestos. This falls in line with an existing assessment of more than 28,000 analytical sample results from asphalt shingles recyclers and recycling projects throughout the U.S. finding that asbestos was detected in approximately 1% of roofing samples, with the majority of the detections resulting from mastic or other non-asphalt shingle material. Because of the historical use of asbestos in other roofing products, an asbestos sampling protocol should be required as part of any asphalt shingles recycling project and the sampling frequency (once per 25 tons) used in this study may be an appropriate starting point for facilities that propose to recycle tear-off shingles in Florida in the future.

Contractors that delivered asphalt shingles to the PCNCLF during the project adhered closely to the required specifications, thus demonstrating the method of communicating the project specifications (routine phone calls and e-mailed specification sheets) was effective. Roofing contractors surveyed after the project indicated the act of separating asphalt shingles from other non-shingle debris at the job site was not a limitation to participation; however, multiple contractors indicated that if the re-roofing job size was too small (less than 20 squares or 2,000 sq ft), the economic incentives at the disposal site were not enough to justify the additional expense of extra containers needed at the job site or the extra hauling trips needed as a result of separating asphalt shingles and non-shingle debris.

Processing the asphalt shingles at PCNCLF was completed through the use of an outside contractor (Dem-Con Companies, Shakopee, Minn.) in less than a day, with a material processing rate of about 33 tons per hour. The processed material, which met the specification required by the HMA facility (General Asphalt, Lakeland, Fla.) in a single pass, was hauled on the day of processing to a HMA facility located 7 miles from PCNCLF. The HMA was created using several ingredients including 5.5% ground asphalt shingles by weight, which resulted in a liquid asphalt cost savings of approximately $5 per ton for the HMA facility.

Approximately 320 tons of HMA was used to pave approximately 1,700 sq yd. in two areas at the PCNCLF. The selected paving areas included one that experiences a light amount of vehicle traffic (a portion of an access road near a lift station) and one that experiences a heavy amount of vehicle traffic (a parking lots adjacent to a new operations building). No issues (e.g., raveling) were noted during the installation of the asphalt, which was completed in one work day. Through 12 months there has been no visible degradation of the two paved areas and the pavement has performed at least equivalently to other paved asphalt areas at the site.

The major technical and economic considerations for solid waste management facilities, roofing contractors and HMA facilities were investigated as part of the project, and a variety of asphalt tear-off shingle recycling approaches were presented, which included varying levels of job-site shingles separation, stockpiling and processing at the solid waste management facility, and stockpiling, processing, and use at the HMA facility. While one or more of the tear-off asphalt shingles recycling approaches presented in this report could be cost effective in different areas in Florida, it appears that the absence of a local or state-level specification to allow processed tear-off shingles in HMA may limit wide-scale implementation of recycling asphalt shingles in this manner. The immediately available market for HMA producers appears to be paving jobs that include neighborhoods, driveways, parking lots and other private road uses. Although no specification exists in Florida for the use of tear-off asphalt shingles in HMA, several neighboring states including Alabama, Georgia and South Carolina were found to have specifications that allowed tear-offs. These specifications were found to be variable with respect to asbestos testing frequency requirements, gradation requirements and use limits within the asphalt mix.

The project team’s next steps will include working with the state and local level road departments or departments of transportation to assess potential research or informational needs to develop a specification that allows the inclusion of tear-off shingles. Through this project, the project team was able to use the collected data and its research to begin an important dialogue with the Florida Department of Transporta-tion. Furthermore, the lessons learned in this project will be used to create a long-term tear-off asphalt shingles recycling program in Polk County and elsewhere in the state.

Powell is operations manager, Innovative Waste Consulting Services, LLC, Gainesville, Fla.; Woolsey is project manager, Jones Edmunds & Associates, Inc., Gainesville, Fla.; Stayer is division director, Waste Resource Management Division,

Polk County, Fla.; and Townsend is professor, University of Florida, Gainesville, Fla., and manager, Innovative Waste Consulting Services, LLC.

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