Environmental issues associated with recycling asphalt shingles
By Timothy Townsend, PH.D., P.E., and Jon Powell, I.L., and Chad Xu, PH.D.

Appeared in C&D World / CMRA January/February 2008

The practice of recycling waste asphalt shingles has gained momentum in recent years. Cited benefits of recycling asphalt shingles include the marketability of materials that can use processed asphalt shingles as a component and the conservation of landfill airspace. However, regulatory concerns over potential environmental impacts, particularly with regard to asbestos, have to some extent limited the widespread recycling of discarded post consumer asphalt shingles. A critical evaluation of data and information related to asphalt shingle recycling was conducted, including a review of available asphalt shingle manufacturer data, federal and state regulations, trade association literature, laboratory data, and data from asphalt shingle recycling facilities. This document reports the results of an effort to summarize relevant information pertaining to possible environmental issues associated with the recycling of discarded (post-manufacture and post-consumer or tear-off) asphalt shingles.

An extensive review found that the primary environmental concern linked to recycling asphalt shingles is the possible presence of asbestos. Asphalt shingles consist of a fiber mat that is impregnated with asphalt, along with other mineral additives. Asbestos is a naturally occurring mineral that, because of its fibrous nature and attributes such as strength and thermal resistively, made it a popular component of many construction products in much of the last century. A review of manufacturer sales literature found that several different types of asphalt roofing products contained asbestos (e.g., mastic, rolled roofing); relative to these other types of asphalt products, asphalt shingles were rarely encountered in the trade literature as containing asbestos. Detailed manufacturing data regarding the amount of asbestos used in asphalt shingles are not available, though anecdotal reports do suggest that asbestos was used in some asphalt shingles until the early 1980s. The expected lifetime of asphalt shingles and the somewhat limited use of asbestos in asphalt shingles suggest that the probability of encountering an asphalt shingle containing asbestos is small. Several shingle recyclers have tested for the presence of asbestos in their shingle supply. Data were compiled from many of these recyclers. Asbestos was detected in just over 1% of the samples (out of more than 27,000 samples). In many cases, the asbestos occurrence was attributed to other materials present in the sample.

Since asphalt shingles are a petroleum-derived product, some questions have been raised concerning the presence of polycyclic aromatic hydrocarbon (PAH), specifically whether ground up recycled asphalt shingles pose either a direct exposure or a leaching risk, or whether the use of recycled asphalt shingles in hot mix asphalt (HMA) production has an impact on PAH emissions. Asphalt does contain small amounts of PAHs, and if shingles themselves are compared to risk-based thresholds for clean soil, a few PAH concentrations may be greater. For applications where ground shingles have been land applied without encapsulation in pavement, this concern has been addressed by blending the shingles with other materials and requiring permitting prior to use of the mixture. The question of PAH emissions from HMA plants using shingles has been raised, but no data exists to suggest that such practices would result in any different PAH emissions relative to HMA using virgin asphalt sources.

The review of existing and available information suggests that recycling of asphalt shingles, especially into HMA, is technically feasible and is likely to offer economic and environmental benefits. The information gathered also suggests that the occurrence of asbestos in tear-off shingles from residential reproofing projects will be minimal, but that the recycling facility operator should expect to encounter asbestos-containing material on occasion and thus should be adequately prepared to monitor and manage such debris. Environmental risks associated with PAH migration appears to be small and comparable to that presented by any asphalt-containing material. Regulatory agencies are faced with the challenge of providing regulations, policies, and permit conditions that provide for protection of human health and the environment, and that are appropriate for the risk presented and not unnecessarily conservative (and thus inhibitory to recycling efforts).

Recommendations
The review of existing and available information conducted for the development of this white paper suggests that recycling of asphalt shingles, especially as a component of HMA, is technically feasibly and is likely to offer economic and environmental benefits. The information gathered also suggests that the occurrence of asbestos in tear-off shingles from residential reproofing projects will be limited, but that the recycling facility operator should expect to encounter asphalt-containing material (ACM) on occasion and thus should be adequately prepared to monitor and manage such debris. Environmental risks associated with PAH migration appear to be small and comparable to that presented by any asphalt-containing material. The data do not exist at the current time to suggest that post-consumer asphalt shingle recycling into HMA should be limited because of concerns of PAHs; for other recycling applications where the shingles are applied directly to the environment, PAH risk should be evaluated within the context of existing waste beneficial use programs.

Regulatory agencies are faced with the challenge of developing and administering regulation, policies, and permit conditions that provide for protection of human health and the environment at recycling facilities, and with respect to the use of the recycled products. Given the environmental benefit of recycling, these requirements should be adequate for the risk presented and not unnecessarily conservative, and thus inhibitory of the recycling enterprise.

Based on our review of the existing information, and how some regulatory agencies and recycling facility operators are managing the risks and benefits associated with this process, the following technical guidelines are recommended for consideration as components in a facility’s operations permit.

An Operations Plan
The operations plan should include the following elements:
- Drawings showing the layout of the facility, including locations of staging and storage areas and equipment. Limitations of the size of unprocessed and processed material piles should be identified.

- A description of how clean asphalt shingle will be sourced. This may include the steps taken to communicate to haulers/contractors that loads with contaminants will not be accepted. Additionally, the plan should include steps that will be taken to communicate with haulers/contractors if they bring unacceptable materials to the facility to prevent future delivery of unacceptable materials.

- A description of the waste screening and identification plan. There should be a demonstration that personnel inspecting the loads will be trained to identify asbestos and asbestos-containing materials, and that this inspector will be on-site at all times that waste is received if the facility is accepting or processing asphalt shingles.

- A health and safety plan that includes an element of asbestos training for all employees (along with training on other appropriate risks as part of operations).

- A description of methods to control storm water run-on and run-off.

- A description of methods to control dust.

- A description of how the asphalt shingles will be processed. This will include providing drawings of the process train, separation equipment, location(s) of waste screeners or spotters, and processing equipment.

- A procedure for maintaining all documentation of incoming materials (tonnage and source), inspection records, sampling history, analytical results, and outgoing finished product (tonnage and end user) to allow review during inspections.

- Identification of routine reporting frequency of asbestos testing results to the regulatory agency. Some states (e.g., Wisconsin) have required annual reporting of asbestos testing results.

A Monitoring and Production Quality Assurance Plan
This plan should include the following elements;
- The methods used by the facility to check incoming asphalt shingle-containing loads.

- The frequency for sampling loads. Loads that have suspected ACM (as identified by the trained asbestos inspector) should be either turned away or segregated and sampled. The load should not be processed until the laboratory results come back, and should only be processed if the material contains <1% ACM.

- The protocol for determining the number of samples once a load has been identified as potentially having ACM. The sampling protocol should follow standard, established procedures (e.g., ASTM standards D 6009-96; D6044-96; D 6051-96; D 4687). At a minimum, one sample of each type of roofing material in the load should be taken.

- Identifications of a certified laboratory that will conduct the asbestos measurement in accordance with the appropriate analytical method (e.g., PLM or TEM).

- A protocol for random sampling of incoming asphalt shingle waste loads. The protocol should identify the sampling frequency and the number of samples taken during each sampling event. Sampling frequency may need to be periodically adjusted based on sample analysis results; the adjustment in sampling frequency may be recommended by the facility owner/operator of the regulatory agency.

- A protocol for random sampling of the processed or finished asphalt shingle product prior to end use. Guidance on finished product sampling frequency has been provided elsewhere (Krivit and Associates 2007).

- Identification of a protocol for managing the load if the laboratory analysis results indicate ACM >1%. If the laboratory results show that ACM is <1%, then the load may be processed as usual.

- Provisions for materials acceptance in the event that a contractor conducted asbestos sampling of a load of asphalt shingles or roofing materials prior to delivery of the load to the processing facility. The sampling and analysis conducted by the contractor must be in accordance with the appropriate ASTM and EPA methods described above, and the asphalt shingle recycler must obtain documentation demonstrating this from the contractor.

- If the processing facility desires to conduct asbestos analysis on site, the facility owner/operator should provide documentation for properly establishing an on-site laboratory that meets the requirements for PLM or TEM analysis.

An End Use Plan
As part of the operations plan, the operator must identify what the final use of the processed product will be, including:
- If the material will be used in an asphalt matrix (e.g., in HMA), the processed asphalt shingle material should be sent to a facility that is permitted to accept such a material. No additional restrictions are recommended.

- If the material will be used in a non-asphalt matrix, the operator should go through their state’s beneficial use determination guidelines (or equivelant) for asphalt shingles to assess the potential exposure risk of the material.

If the beneficial use determination rules specific to asphalt shingles do not exist in the state, seek guidance from the regulatory agency’s contact for beneficial use determinations to evaluate the appropriate beneficial use guidelines that should be followed.

About the Authors
Dr. Timothy Townsend, PE, is a professor of Environmental Engineering Sciences at the University of Florida. Jon Powell and Dr. Chad Xu are environmental engineers with Innovative Waste Consulting Services, LLC in Gainesville, Fla.

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