Thursday, 21 November 2024

Economics and Markets for Recycling Asphalt Shingles

Markets

Recycling asphalt shingles has several environmental benefits and are known to have greenhouse gas savings when compared to landfilling (in terms of metric tons of CO2 per short ton of shingles). Recycling of asphalt shingles are estimated to have economic benefits as well.

The use of grounded recycled asphalt shingles (RAS) in hot mix asphalt (HMA) is by far the most popular method of recycling. This is in part due to the asphalt and aggregate content of RAS and state highway agencies including RAS use in mix specifications [1]. In their cost savings estimates, the National Asphalt Pavement Association (NAPA) assumes an asphalt cement content of 20% and an aggregate contribution of 50%. In 2015 and 2016 NAPA estimated RAS use in HMA contributed to $195 and $103 million in cost savings respectively, based on the tons of shingles recycled and the average cost of virgin asphalt and aggregate in the US [2]. Savings can vary from location to location and depend on factors such as shingle processing costs (e.g. grinding and moving on site), the cost of landfilling, and most importantly, the price of virgin asphalt cement.  A study from the Texas Transportation Institute in 2013 estimated a cost savings between $4.00 and $7.00 per ton of HMA assuming a 5% RAS mixture and $600 per ton of virgin AC [3]. The economic savings of recycling ashpalt shingles can be expected to increase as the cost of petroleum rises. 

Several potential markets exist for asphalt shingles. These include:

  • hot mix asphalt
  • warm mix asphalt
  • porous asphalt pavement
  • cold patch
  • dust control on rural roads
  • temporary roads or driveways
  • new roofing shingles
  • fuel
Listed below is a description of each market and some of the benefits that may be derived from using recycled asphalt shingles (RAS).
Hot-Mix Asphalt (HMA)
The use of RAS in HMA is by far the most popular recycling path with several state highway agencies researching and permitting its use in their mixes. The added asphalt decreases the demand for both virgin asphalt cement and aggregate, while improving the properties of HMA pavement. Cutbacks from shingle factories can be ground up and added to the HMA process or regenerated with rejuvenating chemicals prior to the HMA process. Though states are continuing to research and permit use, several are reducing or setting a more conservative value for the amount of RAS permitted in a mix. Research indicates that a finer grinding (e.g. material less than 3/8”) will create more efficient mixes. Rejuvenators (chemical additives used to rejuvenate properties of aged asphalt binders) are being investigated by states for use in mixes, and some are evaluating the effect of using rejuvenators with RAS. Recent research on use of RAS in combination with finer grinding sizes and rejuvenators has shown positive results on asphalt mix properties, but further research should be performed in this area. NAPA reported in 2016 that 42 states permitted use of RAS in at least some commercial and residential mixes, while 5 states do not permit use of RAS in any mixes [2].
The use of RAS in asphalt mixtures can have benefits aside from resource and greenhouse gas savings. Draindown in asphalt mixtures is when the asphalt binder material loses its binding with the aggregate during transportation or placement and drains down further into the mixture from the surface. The use of fibers in asphalt mixtures has been shown to reduce the level of draindown in mixtures and reinforce the matrix. Fiberglass or cellulose fibers contained in RAS can therefore aid in minimizing draindown in asphalt mixes [4].
 
The use of RAS in HMA can depend on the level of coordination between environmental and transportation agencies in the state. Illinois is one example where RAS is being responsibly used in the production of HMA. Shingle recyclers must be permitted by both the Illinois Environmental Protection Agency and the Illinois Department of Transportation (IDOT) before beginning operation and using the RAS they produce in IDOT mixes. In addition, pursuant to Section 22.54 of the Illinois Environmental Protection Act, landfills cannot accept shingle loads if they are located within a 25-mile radius of a permitted shingle recycling facility. Illinois’ success in roadways was extended to runways in 2014 when the state’s Chicago O’Hare International Airport runways became the first in the country to use RAS with the approval of the Federal Aviation Administration (FAA) [5]. This level of success points to the state’s coordination and responsible management of RAS in the HMA market.
 
On the national level, NAPA continues to survey asphalt pavement producers on the use RAS and summarize its use in their annual survey [2]. In addition to Illinois, other states continue to progress the use of RAS in HMA. The Vermont Agency of Transportation will be including specifications on the use of pre and post-consumer RAS in their mixes in their 2019 specifications [6]. The Wisconsin Department of Natural Resources currently requires recyclers to be approved before sending RAS to an asphalt plant and will be publishing guides for recyclers in the near future [7]. In New York, the State Department of Transportation moved out of trial use and issued specifications allowing RAS in their mixes in 2015 [8]. Finally, in terms of future use, the Delaware Department of Transportation is conducting a study in 2018 to analyze the properties of RAS mixes with and without the use of rejuvenators to find if their use may be beneficial to RAS mixes [9].
 
Warm Mix Asphalt
Some studies have looked at the use of RAS in combination with Warm Mix Asphalt (WMA) technology. Similar to results seen with HMA, RAS is seen as a viable addition to WMA mixes and it helps to improve the rutting resistance of the pavement [10]. A study from Rutgers in 2017 looked directly at how use of WMA would aid with compaction of stiff asphalt mixes that contain RAS. The study concluded that WMA does appear to aid in the ability to compact the mix. Also, a “5 to 20 degrees Fahrenheit reduction in mixing and compaction temperatures can be achieved” for RAS mixes when using WMA [11].
 
Porous Asphalt Pavement
A study conducted in 2011 by researchers for the U.S. Green Building Council was one of the first to look at the use of RAS in porous asphalt pavement. The addition of RAS was believed to add stiffness to the otherwise soft porous asphalt pavement mixture. This property of RAS binder could offset the cost of using a more expensive and stiffer asphalt binder. The study found that mixtures containing RAS had better rutting performance than mixtures containing a higher grade asphalt binder. Brittleness of the RAS mixture at cold temperatures was not evaluated in the study [12].
Cold Patch
Use of RAS in cold patch has been shown to have a longer lifetime than cold patch without. Cold patch containing RAS has been reported in New Jersey, Washington, and California as well as the city of Chicago. The RAS cold patch mix does not “clump” compared to other cold patch mixes and can be applied without heavy equipment to patch potholes [13]. The patches have a longer life compared to other patch materials, likely due to the fibers from the felts or fiberglass in shingles.
Dust Control on Rural Roads
Rural unpaved roads can be sources of noise and dust. Incorporating RAS into the mixture used to cover roads can reduce both disturbances as well as reduce aggregate loss and increase lifetime and decrease maintenance requirements. A study conducted by the Iowa DOT noted that a rural roadway using RAS performed well for at least two years [13].

The use of RAS in rural roads is being studied in Vermont. Currently, Vermont requires recycling of "architectural waste," which includes asphalt shingles, if a project produces more than 40 cubic yards of this waste and is within 20 miles of a facility that recycles it. The Vermont Agency of Transportation (VTrans) and the Vermont Department of Environmental Conservation (VDEC) are partnering on a pilot project which will look at the use of RAS in unpaved roads. The organizations are subsidizing the cost of 3,300 tons of 20% RAS and 80% natural aggregate to be distributed to three municipalities for use as a driving course on unpaved town roads. If the roads are shown to be feasible and beneficial compared to current unpaved conditions, VTrans and VDEC will promote increased shingle recycling and use of RAS/gravel in the future [13].
Temporary Roads or Driveways
RAS has been used in temporary roads, driveways, or parking lot surfaces. RAS is typically ground to 1/4 inch and passed under a magnetic separator in order to sufficiently remove all nails. The processed shingles are spread and compacted for an easily installed surface. In Altus, OK, RAS was mixed with RAP to create a parking lot surface [14].
Aggregate Base
Little research has been conducted into this market, but shingles have been used as part of the sub-base in road construction. Processed shingles may be blended with recycled asphalt pavement and concrete. It is suspected that the addition of RAS may improve the compaction of the sub-base [CIWMB ].
New Roofing Shingles
Using RAS in new shingle production would close the loop on shingle recycling, however, this application is not being heavily pursued. A research project conducted by the Department of Energy and Owens Corning looked at the feasibility of using RAS in different components of new shingle production. One application was applying RAS to the headlap (the half of the shingle tab that is covered during application) with a 15% RAS and 85% virgin mixture. Although the resulting shingles met quality standards, additional costs for transportation and handling are incurred due to the need to mix RAS with raw granules to prevent re-agglomeration of the recycled material increasing the cost of manufacturing [15]. Additionally, a report prepared for the U.S. Department of Energy showed that the addition of up to 20% of recycled shingles did not affect the production of new shingles. They also showed significant energy savings in using RAS.[See Technical Reports]
Fuel
Fiberglass mat asphalt shingles are estimated to have a BTU value between 3,800 and 4,400 BTU/lb making it a good candidate for combustion. The recovery of the BTU value of waste shingles is an established market in Europe but has limited applications in the US [1,16].

 

 

Last Updated: ( Sunday, 10 June 2018 )