Monday, March 1, 2010

How to Incorporate Shingle Recycling

This article was originally published in the February 2010 issue of AsphaltPro magazine. To view sidebars, additional information, and other how-to articles from that issue, contact the circulation department to request a free subscription and copy of February at:
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By Sandy Lender
Not all European roofs use asphalt shingles, but our colleagues in the Eurobitume association could benefit greatly if they did. Asphalt shingles in Europe contain roughly 40 to 60 percent asphalt content. In the United States, newer shingles contain about 19 to 22 percent asphalt. How can an asphalt professional mine this black gold and use it to his or her benefit? Kent Hansen, the director of engineering for the National Asphalt Pavement Association (NAPA), spoke at length about the topic at the 55th annual meeting in Maui, Hawaii. Here are some good ideas he brought up to augment information you’ve found in the pages of AsphaltPro before. Also, please note that NAPA has a new publication titled Guidelines for the Use of Reclaimed Asphalt Shingles in Asphalt Pavements available.

First, bringing state departments of transportation (DOTs) and other agencies up to speed on the benefits of recycled asphalt shingle (RAS) use in asphalt mix design is a battle researchers have already begun. The Energy & Recycling Task Force reported during its Jan. 18 meeting that the NAPA strategic plan’s goal for increased recycled asphalt pavement (RAP) use in 2010 looks much the same as the plan for 2009 but now incorporates the use of RAS. Industry members in Iowa are taking part in a pooled fund study to test the benefits and use of RAS. Other states, mostly in the East, according to Hansen, bring their findings to the table as well. Hansen stated that it takes conversations and cooperation among regulators, DOT officials and contractors to bring good specifications for RAS use into agency documents.

Next, look at the way RAS can enhance your bottom line. As experts have pointed out, there’s a significant amount of asphalt in an asphalt shingle (see sidebar above). While not every state has manufacturers of asphalt shingles, those that do contribute to the approximately 1 million tons of manufacturers’ waste produced annually, according to Hansen. The other source of asphalt shingle material is in tear offs, which producers can find everywhere. That amounts to 10 million tons per year.

When roofing contractors and shingle manufacturers take waste to a landfill, they must pay a tipping fee to leave the waste there. If you can offer them a lower tipping fee, they should be interested in bringing that product to you. But Hansen suggested a variety of factors to consider before going into business collecting trash—even if it’s valuable trash.

Permits and licenses for accepting shingle material vary by state and county. You’ll be required to test for contaminants such as asbestos. While asbestos has been banned from shingle manufacturing since the early 1980s, there are old roofs out there with product that could find its way into your stockpile. There are some mastics and caulking that have trace amounts of asbestos, and you don’t want to accept those into your facility. You need to decide if you’ll accept tear offs with that looming—albeit miniscule—threat. If you choose only to accept manufacturers’ waste, you limit your sources and product availability, but also limit some of the processing worries that we’ll discuss next.

Accepting tear offs opens up your sources and product availability, but also opens up testing and processing challenges. You’ll need to make decisions regarding the condition tear offs must be in when you accept them, and make those conditions clear to suppliers. Will you accept material with flashing and wood attached? Or will you require roofers to remove this excess waste before delivering tear offs? You’ll never get shingles devoid of nails, so be prepared for that element of cleanup in your own facility.

Decide if you’ll restrict supply to only tear offs from private residential homes. This is another way to ensure the shingles you receive are of post-1980s manufacture. You can work with roofers to ensure you get clean material for your operation.

Tear offs must be certified free of hazardous substances and suppliers will arrive with some notice of certification from their testing. This won’t clear you of responsibility. In some states or counties, you’ll need to test the product when it arrives and again at various stages of your operation. For instance, the state of Maryland is reported to have three layers of testing for asbestos once shingles are at the asphalt facility.

It’s wise to pave the area where tear offs will be received and processed on your property, not just for aesthetic reasons, but also to make your job of clean-up easier if a hazardous substance is ever detected. For processing, the first thing to do with shingles is send them through a picking conveyor to remove obvious missed waste. Next is grinding, and the article in the August/September 2009 issue of AsphaltPro refers to a variety of grinding machines available at this time. After grinding, the material goes to a screen or may go back through for grinding again. Next it goes to a mix or a stockpile.

Asphalt shingle surface granules and fill are hard and abrasive on equipment; they wear grinding chamber equipment and create heat. Hansen reminded audience members to balance the amount of water used in cooling equipment. Also be sure you perform grinding in optimal conditions. When ambient conditions are too hot, you risk melting and chunking of material in the equipment.

This leads to thoughts on the stockpiles. As with RAP piles, you want to keep the RAS pile out of direct sunlight if possible to prevent re-agglomeration. An 80/20 blend of sand or RAP in the pile can also help keep re-agglomeration down. Cover the pile to protect it from the weather. When it’s time to make mix, pass the RAS material through a lump breaker or grind it again before feeding it into the plant. The goal is not to grind it further or resize it, but merely to break up any chunks and keep it at its proper size for mixing.

From the testing Hansen reported in January, getting density has proved easier with a RAS mix than expected while providing “a significantly stiffer binder.” Field emission testing has shown SO2 and Formaldehyde “to be non-issues,” although workers reported some odor. There are more tests to do and more to report on, but getting started is the first step. For contractors and producers ready to add RAS to their cost-savings arsenal, the news is good. With the decline in tear offs that contain asbestos, the industry sees another recycled product that can enhance the HMA or WMA mix while keeping waste out of landfills and materials costs under control.

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