Millions of tons of roofing waste end up in landfills each year, with tear-off asphalt shingles representing a significant portion. However, a growing body of evidence demonstrates that these Roofing Shingles can be diverted from disposal and recycled into hot mix asphalt (HMA) pavement. Companies in Minnesota and across the United States have invested in sorting, grinding and cleaning equipment to turn this waste into a valuable resource for road construction. This article examines the technology, economics and regulatory framework behind recycling tear-off asphalt shingles into HMA pavements.
The Case for Recycling Tear-Off Shingles
The volume of roofing waste is staggering. A single Minnesota landfill receives approximately 50,000 tons per year, according to Dem-Con Recovery and Recycling, which has invested heavily in shingle recycling infrastructure. One study indicated statewide tear-off shingles recovery could reach at least 156,000 tons per year, and current volumes are likely higher given continued population growth and roof replacement cycles.
Why Asphalt Shingles Are Suitable for Pavement
Tear-off asphalt shingles contain at least 20 percent asphalt cement binder by weight, making them an attractive substitute for virgin liquid asphalt in HMA production. They also contain aggregate and mineral filler that can contribute to the pavement mix. Unlike manufacturers’ scrap shingles, which have been permitted for HMA use since 1996 in Minnesota, tear-off shingles require additional sorting to remove contaminants such as nails, wood, plastic and paper accumulated during installation and removal.
Environmental and Landfill Benefits
The environmental benefits of recycling tear-off shingles include:
- Reduction of landfill space consumption, extending the operational life of existing disposal facilities
- Conservation of virgin asphalt binder, a petroleum-derived product with a significant carbon footprint
- Energy savings equivalent to approximately 200 kilowatt hours of electricity for every ton of tear-off asphalt shingles recycled
- Lower greenhouse gas emissions compared to producing and transporting virgin asphalt materials
- Reduced demand for aggregate mining and quarrying operations
Jason Haus, vice president of Dem-Con, framed the opportunity clearly when he stated that recycling tear-off shingles represents a significant new step forward in abating the need for landfilling shingles. The company has invested in a new shingle grinder and a sorting and cleaning system specifically to meet material specifications that HMA producers require.
From Roof Waste to Road Material: The Processing Journey
Converting tear-off asphalt shingles into a usable recycled product for HMA involves several distinct stages. Each stage is critical to producing a consistent, high-quality material that can meet the demanding specifications of modern pavement construction. The quality and cleanliness of the recycled asphalt shingles (RAS) will differentiate companies that are looking to enter this market, according to industry professionals involved in the Shakopee, Minnesota demonstration project.
Collection and Sorting
The first step in the recycling process is collecting tear-off shingles from roofing contractors and bringing them to a dedicated processing facility. The material arrives mixed with various contaminants that must be removed before grinding can proceed.
- Manual presorting: Large debris items such as lumber, metal flashing and whole rolls of underlayment are removed by hand or with mechanical equipment
- Magnetic separation: Steel nails and other ferrous metals are extracted using powerful overhead magnets
- Air classification: Lightweight materials such as paper, plastic and wood particles are removed with air knives and vacuum systems
- Final inspection: Quality control personnel verify that the cleaned material meets contaminant thresholds before it moves to grinding
Grinding and Sizing
Once cleaned, the shingles are fed into a specialized grinder designed to reduce the material to a fine, uniform consistency. Rotochopper Inc., the equipment manufacturer that supplied Dem-Con with its RG1 grinder, has demonstrated that their machine can produce a high-quality, finely ground RAS product in a single pass. This is an important efficiency advantage because it reduces processing time and operating costs.
The ground RAS must meet particle size specifications that HMA producers require. Typical specifications call for the majority of particles to pass through a certain sieve size, ensuring that the recycled material blends uniformly with virgin aggregate and binder during mix production.
Quality Control and Material Testing
Producing a consistent RAS product requires ongoing quality control testing. Key parameters that must be monitored include:
| Parameter | Importance | Typical Specification |
|---|---|---|
| Asphalt cement content | Determines binder contribution to HMA mix | 18-22% minimum |
| Moisture content | Affects plant production rate and fuel consumption | Less than 5% |
| Particle size distribution | Ensures uniform blending in HMA | 100% passing 3/8 inch sieve |
| Contaminant level | Prevents pavement performance issues | Less than 1% by weight |
| Fiber content | Can affect mix workability and compaction | Varies by specification |
Vince Hundt, vice president of Rotochopper, noted that recyclers like Dem-Con will be able to sell a valuable recycled product to HMA producers once they consistently meet these material quality standards. The cleaning and sorting process to eliminate foreign debris is critical in producing a high quality RAS.
Performance Testing and Real-World Demonstrations
Before tear-off shingle recycling could be considered for mainstream use, the material needed to prove itself in real pavement applications. Minnesota has been at the forefront of this effort, with the Minnesota Department of Transportation (MnDOT) participating in five separate demonstration projects that successfully incorporated tear-off shingles into HMA pavements. These demonstrations provided critical data on mix performance, workability and long-term durability.
The Shakopee Demonstration Project
The most recent demonstration, held in Shakopee, Minnesota on October 21, was sponsored by Dem-Con Recovery and Recycling and Commercial Asphalt Company. Plehal Blacktopping installed the asphalt pavement at Dem-Con’s Shakopee plant. Jack Van Remortel, president of Plehal Blacktopping, reported that his paving crew did not notice any difference when working with the RAS-modified mix. The bituminous mixture was installed using normal equipment and procedures.
This finding is significant because it demonstrates that tear-off shingle recycling does not require specialized paving equipment, additional training or modified construction techniques. The material can be handled exactly like conventional HMA, which lowers the barrier to adoption for paving contractors.
Mix Design Considerations
Commercial Asphalt Company, a subsidiary of Tiller Corp., has used reclaimed asphalt pavement (RAP) for over 20 years. This experience positioned them well to evaluate RAS in HMA mixes. Robert Kuehborn, manager of Product Design and Quality Control, confirmed that recycling tear-off shingles is a proven, feasible technology that can conserve asphalt cement and save money.
Key mix design considerations when incorporating RAS include:
- Adjusting the virgin binder content to account for the aged binder contributed by the RAS
- Verifying that the combined aggregate gradation meets the target mix design
- Testing for moisture susceptibility and rutting resistance
- Ensuring adequate compaction characteristics for the intended pavement layer
Comparing RAS with Other Recycled Materials
The asphalt industry already has extensive experience with recycled materials, particularly reclaimed asphalt pavement (RAP). The successful track record with RAP provides a template for integrating RAS into standard practice. For contractors and producers looking to expand their sustainable material options, understanding the differences between various recycled products is essential. Resources such as Solar Shingles a Comprehensive Overview and Solar Panels Vs Solar Shingles provide useful context on how different roofing and energy technologies intersect with sustainable construction practices.
Specifications, Economics and the Path Forward
The single largest barrier to widespread adoption of tear-off shingle recycling in HMA is the absence of a permissive materials specification from state departments of transportation. Without such a specification, HMA producers cannot use RAS in certified mixes that are purchased for state-funded road projects, which represent the bulk of the market.
The Role of MnDOT Specifications
MnDOT has been a national leader in recycled material specifications. In 1996, the department adopted a specification for the use of manufacturers’ shingle scrap in HMA, becoming one of the first state DOTs in the country to do so. This “new” shingle scrap comes from the three shingle manufacturers located in Minnesota and has been used successfully in HMA for years.
Jason Haus of Dem-Con explained that the next needed step for large scale recovery of tear-off shingles is a permissive MnDOT specification similar to the one granted for manufactured scrap shingles. Without this specification, valuable tear-off shingles will continue to be landfilled even though the processing infrastructure is ready and willing to supply HMA producers.
MnDOT is currently considering how best to write requirements for an updated materials specification that would allow tear-off shingles in HMA. The department has already participated in five successful demonstrations, providing a strong evidence base for the specification development process.
Economic Analysis of Shingle Recycling
The economics of tear-off shingle recycling are compelling when examined at scale:
- At least 156,000 tons of tear-off shingles could be recovered per year on a statewide basis
- With an oil content of at least 20 percent, recycling shingles could conserve approximately 32,000 tons per year of binder
- Using a conservative price estimate of $400 per ton of liquid virgin binder, the savings is equivalent to about $12.5 million per year
- Additional savings come from reduced landfill tipping fees paid by roofing contractors
- Energy savings of approximately 200 kilowatt hours for every ton of shingles recycled further strengthens the economic case
Kuehborn noted that part of these savings can be passed to the driving public, meaning taxpayers funding road projects benefit directly. He emphasized that tear-off shingles should be accepted as a standard recycled material in HMA, similar to how RAP and manufacturers’ shingle scrap are treated by MnDOT today.
Industry Readiness and Capacity
The recycling industry has already demonstrated its readiness to handle large volumes of tear-off shingles. Dem-Con invested in a new shingle grinder and a sorting and cleaning system specifically to meet the quality standards that HMA producers require. Rotochopper’s RG1 grinder has proven capable of producing a finely ground RAS product in a single pass, and the equipment is commercially available for other recyclers to deploy.
Commercial Asphalt Co. has confirmed they have the capacity to incorporate RAS into production at full scale. The combination of ready processing infrastructure, proven production capability and willing paving contractors means the supply chain is essentially complete, awaiting only the permissive specification to unlock the market.
Looking Ahead: The Future of Shingle Recycling
As more states develop specifications for tear-off shingle use in HMA, the RAS market is expected to grow. Contractors interested in sustainable paving practices should monitor specification developments and consider investments needed to participate. Understanding the full range of sustainable Roof Shingles options, from recycling to solar-integrated products, helps professionals make informed decisions about material selection and waste management.
Haus predicted that once the permissive specification is in place and virgin asphalt prices remain high, land disposal of shingle material will become rare. The industry is prepared to provide RAS on a large scale, turning a waste problem into a sustainable solution benefiting the environment, the economy and the driving public alike.