Recycled Asphalt

Nearly 11 million tons of asphalt shingles are scrapped each year; 10 million from installation tear-offs and re-roofing jobs and another one million discarded as waste by asphalt shingle manufacturers. The Environmental Protection Agency estimates that shingle waste makes up 8 percent of the total building-related waste stream and 1 to 10 percent of annual construction and demolition debris, representing a tremendous burden to landfills across the country.

Asphalt, compared to other construction materials is a prime candidate for recycling, recycling facilities have responded and started developing new ways that could save money and recycle the discarded asphalt. If only 5% of recycled asphalt was put into hot mix asphalt used to pave roads it is estimated that $1 to $3 per tonne could be saved, not to mention that the quality of the mix would improve.

Seeing the amount of shingles, and asphalt being dumped in landfills that could be re-used, Mark Pahl founded Dem-Con Shingle Processing. The company was founded in 1985 and at first the business was mainly a construction and demolition debris landfill. Over the years, the landfill reclamation and recycling 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.”

By using a percentage of recycled shingles in hot mix, it can improve the quality of the pavement by increasing its resistance to wear and moisture, and decreasing deformation, rutting and thermal fatigue and cracking. “From our local level each year we process about 10,000 tons (8928.6 tonne) 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 (22,321.4 to 35,714.3 tonne) that used to go directly into the landfill. And that’s just at our Shakopee location. Imagine the effect nationwide.” Pahl is excited that shingles can now be used for good use instead of just ending up in the landfills.

When recycling shingles, they must be pure asphalt. “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.”

In many of the States recycling shingles is becoming better known, the Department of Transportation (DOT) in many states has decided to change “When we were getting this started a lot of state DOTs didn’t have a hot-mix spec using shingles, but more and more are coming online,” Pahl says. “Whatever the DOT spec is, we are able to meet it. We’re competing with virgin asphalt because that’s what the asphalt recovered from the shingles replace. Using shingles in the mix allows the hot mix producer to lower the use of the high-price virgin asphalt. So it’s really a cost savings to them and this is what enables this process to be economically viable.”

Not only do using recycled shingles help the pavement, it helps save money and also helps the environment.

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