Hennepin County Recycles rooftops into road surfaces

Hennepin County is grinding up and recycling asphalt shingles in more road paving, saving money in the process.

In Hennepin County, the roof that was once over your head increasingly is becoming the road under your tires.

The county's new solid waste master plan calls for increased use of shredded asphalt shingles in the mix of material that's used to repave roads. The county has been using recycled shingles in asphalt mixes since 2002, with good results.

The goal is to keep the shingles out of landfills, because they contain chemicals and they don't decay for a very long time, if at all.

"Whether it's cardboard, plastic, paper or shingles and building materials, our No. 1 goal is to divert as much waste as possible," said Dave McNary, the county's assistant director of environmental services.

No numerical goal for shredded asphalt use is included in the plan, but the county's Chris Sagsveen said the county uses the material when it can. Sagsveen, division manager for road and bridge operations, said asphalt with 5 percent shredded shingle content is cheaper than virgin asphalt.

With oil prices spiking, the savings from using the shingle mix add up. When part of Franklin Avenue in Minneapolis was resurfaced last year, the bituminous mix that was used contained recycled shingles and cost $39 per ton, about $3 less than conventional mix. That saved more than $13,000.

"It appears to be as durable as our regular mixes," said Steve Peterson, technical coordinator for county road and bridge operations. "It's very compatible; it has oil and grit in it but adds a recycled component."

State Department of Transportation standards dictate that no more than 5 percent of a bituminous mix be made up of recycled shingles, partly because the shredded shingles are so fine. Peterson said the product resembles sand, and paving materials need a mix of big, medium-sized and fine fragments to bind properly.

While MnDOT used to require that only shingles that were manufacturer scrap be used in paving mixes, since 2010 it has accepted tear-off material as well. Processors screen old roofing for nails, wood and other debris before it is shredded.

According to MnDOT, mixes containing shredded shingles wear as well as regular paving materials. Because recycled asphalt also is acceptable, some bituminous mixes contain as much as 30 percent recycled material, Peterson said.

The county's main challenge in using more of the shingle mix may be the competition for the material. Companies that process the recycled shingles are finding demand high.

McNary said transfer stations that accept construction materials now report that they recycle about 75 percent of that material, including shingles.

"Before, you had a hard time convincing people that you could use shingles for this," McNary said. "Now there is more demand than the supply of shingles."

Mary Jane Smetanka • 612-673-7380 Twitter: @smetan

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