Public Works Officials Warm Up to Cold in-Place Asphalt Recycling

When it comes to battling global warming, any technique with “cold” and “recycling” in its name is bound to be beneficial. So when MTC teamed up with the city of Napa to stage a demonstration of “cold in-place recycling” of asphalt pavement in mid-October, Bay Area public works officials were all ears. The process involves just what its name implies: digging up old asphalt and recycling it on the spot, at relatively ambient temperatures.

A series of three units on wheels — which are linked together to form a 142-foot asphalt recycling  “train”  — do the job of removing the asphalt to the specified depth, grinding it up and mixing it with an emulsion that rejuvenates the mixture in a portable asphalt recycling plant, then repaving the roadway in a single pass.  

“It takes the agency’s old, distressed asphalt and recycles it into new asphalt base that’s ready for a surface treatment,” said James Emerson, a representative of Pavement Recycling Systems, Inc. of Mira Loma, California, which performed the Napa demonstration.

Under the conventional hot-mix asphalt system, jurisdictions need to remove the old asphalt and haul it away, pay to dump it (and in the process use up precious land fill), then pay for the new asphalt to be processed, trucked back and installed, according to Emerson. “For one mile of roadway at 12.5-feet wide and at a depth of three inches, you would require 83 truck loads, exporting and importing the material. For cold in-place recycling you would use two truck loads to bring in the engineered emulsion for the recycling process, thereby saving 81 truck trips for the same one-mile stretch,” Emerson said.

While new to the Bay Area, cold in-place recycling has enjoyed success in Europe and Canada as well as in Southern California and most other states across the U.S., according to Emerson.

In addition to eliminating back and forth truck traffic, the process reduces energy inputs into the manufacturing process and eliminates the need for mining and production of virgin materials. MTC staff have calculated that the region could cut carbon dioxide emissions by 354 million pounds over the next five years by applying the technique to appropriate roadways — equivalent to taking 29,172 cars off the road for one year. The technique not only is better for the environment, but also is faster and easier on city coffers, costing 40 to 50 percent less than traditional paving methods and stretching impacted city budgets further.

Public works officials from around the region descended on the city of Napa on October 13 to witness the demonstration, which was funded with $2 million in federal money provided through MTC’s Innovative Climate Grants Program. Also benefiting from the grant is Sonoma County, which staged a demo in a more rural setting earlier in the month. A portion of the grant will go toward educating local public works departments about the method. 

 – Brenda Kahn