The Northeast Recycling Council estimates that more than 11 million tons of asphalt shingles are scrapped in the U.S. each year; 10 million from installation tear-offs and re-roofing jobs and another one million discarded as waste by asphalt shingle manufacturers. The U.S. Environmental Protection Agency estimates that shingle waste makes up eight percent of the total building-related waste stream and one to 10 percent of annual construction and demolition debris, representing a tremendous burden to landfills across the country.
Due to their material composition (asphalt versus wood, metal and other construction materials), shingles are usually separated from other construction-related waste debris, making the discarded roof protectors a prime candidate for the recycling stream.
Recycling facilities have responded, and new technology has created some money-saving opportunities for recycled shingle markets - most notably as an additive to asphalt paving preparations. Using hot mix asphalt with only 5 percent recycled shingle material can save $1 to nearly $3 per ton of hot mix asphalt (HMA), as well as improve the quality of HMA used in paving.
Concerned by the quantity of discarded construction debris that was ending up in the country's landfills and knowing that a lot of it could be put to good use, Mark Pahl saw an opportunity and founded Dem-Con Shingle Processing.
Dem-Con is born
Dem-Con Companies, LLC, based in Shakopee, MN, was founded in 1985 and, at first, its business was mainly a construction and demolition debris landfill. Over the years, the landfill has evolved to not only demolition and construction debris, but also certain types of industrial wastes and impacted soils.
"Basically, we handle all non-hazardous waste, with the exception of household trash," Pahl says. "Construction and demolition material is still the primary focus and the largest portion of our business. We encompass an area that includes the Minneapolis/St. Paul metro along with surrounding rural communities. We process a lot of different types of construction debris before it enters the landfill, which includes pulling out wood, metal, cardboard, concrete, asphalt, etc. There is a lot of value in removing those materials prior to landfilling."
Researchers have found that using recycled asphalt shingles in HMA can actually improve the pavement's performance by increasing its resistance to wear and moisture, and decreasing deformation, rutting and thermal fatigue and cracking. Currently a substantial portion of asphalt shingle recycling involves mixing five percent ground up shingles with HMA used in road paving and cold patch applications. Pahl is excited by not having to landfill shingles anymore.
"From our local level each year we process about 10,000 tons of manufacturing scrap," Pahl says. "That material that comes right from the shingle manufacturer as factory rejects or end runs. Add to that additional scraps from reroofing existing homes, hailstorms, demolition, etc., and the amount increases to somewhere between 25,000 up to 40,000 tons that used to go directly into the landfill. And that's just at our Shakopee location. Imagine the effect nationwide."
Enlisting a wood-processing trommel for assistance
According to Pahl, the material that Dem-Con receives as factory rejects is ready to be processed without any special preparation because the material is void of any contaminants or construction debris.
Shingles originating from reroof projects create a bit more of a problem and necessitate some cleaning and filtering of other materials since this debris often arrives at his facility mixed with a variety of other substances, including tin, metal, roof vents, boards, etc.
"We remove all the debris that doesn't contain asphalt on a sorting line," Pahl explains. "Essentially the material is spread out on a conveyer belt and we have laborers that manually remove all non-asphalt containing materials as they move along the sort line. From there, the shingles are ready to be ground. Generally the grinder then directly feeds the material to a trommel screen to create the desired end product used for the asphalt hot mix."