Sunday, 20 October 2024

Overview

Overview of Asphalt Shingle Recycling 
William Turley
Executive Director
Construction Materials Recycling Association
 Introduction
Asphalt shingle recycling is a growing, dynamic, and environmentally friendly industry that promises to divert millions of tons of materials from landfills while providing businesses an opportunity to make a profit and employ people. But how to get the shingles, how to process them once you have them, what problems will be encountered when processing them, and most importantly, what markets are available for the finished products are among the questions regarding the practice. There is no definitive tome on the subject, which is why the Construction Materials Recycling Association, with funding from the U.S. EPA Region 5, developed this site. Here you will find a tremendous amount of information about the recycling of asphalt shingles.

Asphalt shingle recycling has been called the next big thing in C&D recycling. An estimated 11 million tons of waste shingles are generated every year in the United States. The overwhelming majority of them are post-consumer, mostly from tear-offs. There is a limited amount of asphalt shingle recycling going on in North America at this time, for a variety of reasons including:

  • Resistance in the marketplace. Some potential markets do not want to try the material, or say it is not economical;
  • Lack of specifications for those markets. Some work has been done in that area, and more is being undertaken now;
  • Fear of hazardous contaminants in post-consumer shingles. The largest concern centers on asbestos.
  • Governmental regulations. Some of these are related to contaminants, some caused by regulator perceptions
Markets
Large-scale recycling of asphalt shingles is a relatively new industry to North America. The shingles have been recycled for years in Europe where several markets are active, including the following, which are also in the United States:
Hot mix asphalt (HMA)
This is considered by many to be the best potential market for recycled asphalt shingles. When asphalt shingles are new they contain anywhere from about 20% to 36% liquid asphalt. Recycling waste generated by the shingle manufacturing process can yield that valuable, petroleum-based product back when used as an additive for hot-mix asphalt. In addition, the small aggregate pieces used for shingles tend to be cubical, a superior shape for binding in road surfaces.
A few official, state-DOT sponsored studies have shown the benefits of using as much as 5% or more recycled manufacturers’ waste back into new HMA (see research section for these studies). According to the National Association of Home Builders (NAHB), 10 states allow for the material to be used on DOT jobs (list resource).The advantages of using manufacturers' waste shingles, rather than post-consumer, in hot mix asphalt is that the infeed has a more uniform level of emulsion and aggregate, making it easier to provide consistent mixes, the kind best suited for highway jobs.  
An example of this concept is done by a shingle recycling and asphalt paving company near Minneapolis. Manufacturers’ waste is ground to 1/4 in. and usually fed at a rate of 5% by volume, sometimes 10%, into the hot-mix plant. The product is used for commercial jobs and in St. Paul, where the city street commissioner allows its use on city streets. The only problem the company has had was when it only ground the shingles to 3/8 inch before feeding theminto the hot mix, and sometimes tabs would slip through and stick up in the pavement. The company now grinds itto 1/4 inch, and nobody can tell the difference between regular asphalt and the recycled shingle one, neither the graders, nor the paving crew.  
Tear-off shingle waste has been used successfully for hot mix asphalt. A paving company in San Jose, CA, used the material in its hot-mix plants. A company representative said, “We did several tests, some with just shingles added, some with shingles and RAP. All the passes we paved with them are still holding up, and they have been in place for several years.”  
Some hot-mix plant operators are still resistant to adding shingles to their mixes, report some recyclers. They say they have enough recycled asphalt pavement (RAP) in there already, or that it is not economically feasible. Also, older plants often are not equipped to properly handle the shingles safely.
Temporary roads, parking lots, driveways
Under these related applications, recycled shingles are processed to a certain size and spread over a designated area to provide a surface on which to drive. Because the specifications are less strict than hot-mix asphalt, this is a common market for post-consumer shingle waste.
Temporary roads, etc., have been done several times, in several ways. One interesting application in Harvard, IL involved a manure spreader for farming that was used to lay down tabs of manufacturers’ waste, followed by a roller to tamp them down. It worked well with the tabs, and requires no grinding. But that is unique. Most of the time, some type of grinding needs to be done in order to get the material to a good size to lay down and compact. Commonly this has been a coarse grind, about to 2 in. minus or so. Caution is advised, however, especially with post-consumer shingles as they contain nails and other metals. One large mixed C&D waste recycler that contracted out shingle grinding, was not told by the subcontractor that the magnet on the grinder was not working that day. The processed material was laid down as dust control on a gravel road near some ballparks. The result was about 20 tire punctures and some sensationalist stories on local television.  
Usually the waste shingle is put through either a tub or horizontal feed grinder, as impact crushers have been tried and found lacking for the application. One exception to that was developed by the late Kenneth Pixley in Altus, OK, where he put a load of shingles in an impactor, along with a load of RAP (Construction Materials Recycling, Vol 1, No. 20). The final product made a great parking lot material, and this practice is being continued today by a few recyclers around the country.
Roadbase
Not commonly used by itself as base, processed shingles are blended in with RAP and concrete by some recyclers to make a roadbase product. The material does provide some added bonding to the product.  
Fuel
The recovery of the fuel value of waste shingles is a well-established market in Europe. Only recently has the concept been tried in the United States, reportedly under controversy because of concern over emissions. Yet the technology exists to make it safe, and with fuel prices going up, this may become a more lucrative market.  
Cold patch mix
Ground shingles can be used alone or mixed with virgin asphalt or other materials as a patch material on roads. Some recyclers report they have had success developing the product.  
Molded products
Examples include parking blocks and stepping stones. These are small markets that probably will just stay niches, but could provide another outletto shingle recyclers.
Specifications
As stated, several states have developed specifications for shingle use in HMA mixes. And some hot-mix plant operators have created their own mix designs using the material, mostly for off-spec work. But, like recycled concrete, there is no one size and performance specification for recycled shingle use in HMA, either size or performance.
Contaminants
A main stumbling block for increased shingle recycling in the United States is the perception that shingles may contain contaminants such as asbestos at levels that are of regulatory concern. There is a lack of understanding by state and local regulatory officials of waste shingles’ properties.
It is acknowledged by the asphalt shingle manufacturers that between 1963 and the mid 1970s, some of them did use asbestos in the fiber mat of their shingles. How many batches of asbestos-tainted shingles were sold as a fire-retardant product and where they were used is information the manufacturers will not divulge, for the obvious reasons of potential asbestos litigation. But the amount of asbestos used in shingles was between 0.02% and 0.00016%, and it was only in a small portion of the manufacturers’ production (NAHB).		  
Thousands of test results of incoming asphalt shingle loads to recycling centersare available from several asphalt shingle recyclers across the country. We have compiled those tests in the section on the presence of asbestos in asphalt shingles on this website. Overwhelmingly, they show the incidence of contaminated loads to be minimal. Most sites testing report no hot loads, and some are no longer even are required to check for the material. Others that do find it are reaping small amounts.

 

Last Updated: ( Monday, 08 March 2010 )