Hawaii Paved a Road With 195,000 Recycled Plastic Bottles and Fishing Nets

Thousands of drivers on West Oahu's Fort Weaver Road have been rolling over a stretch of pavement made partly from plastic equivalent to 195,000 recycled bottles without knowing it, and scientists are now scrutinizing every inch of it.

The Hawaii Department of Transportation, working with researchers at the National Institute of Standards and Technology and Hawai'i Pacific University, has been running what Building Industry Hawaii called the state's first hot mix asphalt plastics project. The pilot road, split into three distinct sections, incorporates polyethylene recovered from discarded Pacific fishing nets and plastic pulled from Honolulu's residential recycling containers, blended into standard asphalt mixes. Despite the striking origin of the materials, the recycled plastic content amounts to just one-tenth of one percent of the total asphalt product by weight.

The three test sections each use a different formulation. The first serves as a control, using traditional asphalt with a styrene-butadiene-styrene polymer binder, the type already common on Hawaiian roads for decades. The second adds a top coat of recycled plastic over the same SBS-modified base. The third uses recycled plastic without any additional modified binder. After approximately 11 months of regular traffic, NIST biologist Jennifer Lynch led a team, including students from Hawai'i Pacific University, to collect road dust samples from each section to test for microplastic shedding that could contaminate surrounding soil. A separate University of Hawai'i at Mānoa group is conducting mechanical testing to assess how each section holds up to traffic and weather. All samples have been collected but results are still being analyzed.

The project grew directly from Hawaii's struggle to manage the ocean plastic washing onto its shores. HDOT Director Ed Sniffen explained the thinking in an appearance on the AASHTO podcast. "We pull tons of trash and plastic waste out of our oceans annually. A lot of fishing nets come through and we started looking at those materials," Sniffen said. "We wanted to see how we could repurpose them rather than burn them or bury them at our landfills. How could we repurpose them to make our pavements better?"

The logistics behind the pilot reveal a broader infrastructure taking shape. Hawai'i Pacific University's Center for Marine Debris Research, which describes itself as operating the state's first marine debris Plastic Recycling Research Facility, collects debris from partner sites on Kaua'i, Maui, and Hawai'i Island, ships it to a Honolulu warehouse twice yearly, and sorts it by type and polymer. For the road project, a U.S.-based company, not publicly named in the research materials, converted the collected marine and residential plastics into a form suitable for incorporation into asphalt. Debris that cannot be recycled is routed to a separate Nets-to-Energy program, incinerated through a partnership with Radius Recycling, POP Fishing and Marine Supply, and Covanta's H-Power facility to generate electricity for the City and County of Honolulu.

Early assessments, while not yet quantified, suggest the approach has merit. Researchers described the results so far as showing these recycled materials may provide a viable end-of-life path for the region's plastic waste. NIST has flagged that future projects could include test roads built specifically from derelict fishing nets and gear removed from the ocean and Hawaii's shorelines, depending on what the current analyses reveal.

The stakes extend well beyond road performance. If the pavement holds and the microplastic data comes back clean, Hawaii could have a replicable model for turning one of its most persistent environmental problems into the ground beneath its feet.