하와이, 재활용 플라스틱과 어망으로 만든 아스팔트 테스트

Hawaii tests asphalt made with recycled plastics and fishing nets for shedding Hawaii has a plastic problem. The island state faces economic and logistical challenges in recycling plastic waste, including marine debris that lingers in its ocean waters. Researchers in Hawaii are pioneering a method to recycle the islands' derelict fishing nets and residential plastic trash into asphalt roads. Early demonstrations show that these recycled materials may provide a viable end-of-life fate for the region's garbage. Jeremy Axworthy, a researcher at the Center for Marine Debris Research (CMDR) at Hawaiʻi Pacific University, will present the team's results at the spring meeting of the American Chemical Society (ACS). ACS Spring 2026 is being held March 22–26; it features nearly 11,000 presentations on a range of science topics. "This work investigates whether it's responsible to use recycled plastics in Hawaii's roads," shares Axworthy. "By reusing plastic waste that is already in Hawaii, we can reduce the environmental and economic impacts of transporting waste plastics from the islands, incinerating it or dumping it in Hawaii's overflowing landfills." Since 2020, Hawaii's roads have predominantly been paved with polymer-modified asphalt (PMA) to increase pavement strength and durability. Compared to standard asphalt pavement, PMA pavement is more elastic and more resistant to cracking, rutting and water damage—qualities that are especially important for the state's tropical climate. PMA pavement is made by first melting pellets of styrene-butadiene-styrene (SBS; a type of copolymer) into a sticky, petroleum-based asphalt binder. Then, the PMA binder is tumbled with heated aggregates (rocks and sand) in a mixing drum, causing the PMA binder to fully coat the aggregates. But why not see if discarded plastics could be incorporated into asphalt pavements as an environmentally friendly disposal option? How would modified pavements made with recycled plastics perform, and would they release microplastics or associated chemicals into the environment? These are the questions the Hawaii Department of Transportation (HDOT) aimed to answer when they reached out to environmental chemist Jennifer Lynch, CMDR director and team lead. HDOT asked Lynch's team for two things. The first was to provide derelict fishing nets removed from Hawaii's marine environment for the creation of recycled plastic-modified asphalt pavements. "Foreign plastic derelict fishing gear is the largest contributor of Hawaii's marine debris problem," shares Lynch. "To date, CMDR's Bounty Project, which pays a financial reward to licensed commercial fishers for marine debris removal, has removed 84 tons of large, derelict fishing gear from the Pacific Ocean." HDOT's second request was to measure possible microplastic shedding from pavements made with plastic waste versus that from standard SBS-modified pavement. "CMDR's laboratory is equipped with state-of-the-art chemical instrumentation for quantifying and characterizing microplastics in environmental samples," explains Lynch. "This capability is incredibly unique and impactful, especially when coupled with our marine debris-removal project and our mission to recycle the debris into long-term, locally necessary infrastructure products." Once a U.S.-based company converted the waste into products that could be incorporated into asphalt, HDOT took the experimental asphalt mixes to Hawaii's streets. A local paving company laid down sections of a residential road on the island of Oahu with asphalt pavement containing standard SBS, repurposed polyethylene from Honolulu's recycling containers and polyethylene from fishing nets. After about 11 months of regular traffic usage, Lynch's team stepped in to collect road dust samples from each section of pavement to test for microplastic shedding, which could contaminate the surrounding soil. The researchers processed the road dust using a method that separates different types of polymers from other materials in the dust, including microplastics, larger chunks of plastic and tire rubber. Using pyrolysis gas chromatography-mass spectrometry (Py-GC-MS), they identified and measured the source of the polymers: styrene and butadiene from the standard PMA, polyethylene from the plastic-waste and fishing-net PMA, and isoprene and butadiene rubber from tires. Initial tests showed that pavements made with recycled polyethylene did not release more polymers than the control pavement made with SBS. Lynch's team showed this was true during mechanical performance tests with pavement samples as well as in simulated stormwater collected from the experimental road sections. Microplastic-sized particles were detected, but very few of these were identified as polyethylene regardless of the pavement type tested. This is likely because the polymers are melted into the asphalt binder, meaning particles that break off are not plastic alone; they are a mixture of rock, binder and melted po