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Hawaii has started testing asphalt with recycled plastic from household waste and fishing nets removed from the sea, in an experiment that evaluates performance, possible release of microplastics, and the local use of waste that today pressures landfills and challenges recycling on the islands
Researchers and authorities in Hawaii are testing a new use for plastic waste and abandoned fishing nets: transforming them into asphalt for street paving. The proposal aims to tackle both the recycling challenges in the archipelago and the accumulation of marine debris and residential plastic waste.
The initiative brings together the Marine Debris Research Center at the University of Hawaii Pacific and the Hawaii Department of Transportation, which has begun investigating whether utilizing this material in pavements could be a more environmentally and economically viable alternative. The team assesses both the performance of the mixture and the possible release of microplastics and other associated substances.
Jeremy Axworthy, a researcher at the center, will present the results of the work at the American Chemical Society’s spring meeting, held from March 22 to 26, 2026. The meeting features nearly 11,000 presentations on various scientific topics, and the group’s study examines whether the use of recycled plastics in the state’s roads can be done responsibly.
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According to Axworthy, the proposal stems from a concrete problem faced by the archipelago: the costs and logistical difficulties associated with the transportation, incineration, and final disposal of plastic waste. By repurposing the existing material on the islands, the project seeks to reduce the environmental and economic impacts caused by these alternatives, as well as the pressure on already overloaded landfills.
Asphalt, Hawaii, and the search for a local solution
Since 2020, Hawaii’s roads have been predominantly paved with polymer-modified asphalt, known as PMA. This type of pavement is adopted to enhance the resistance and durability of the surface, with characteristics considered important for the state’s tropical conditions.
Compared to conventional asphalt, PMA is more elastic and has greater resistance to cracking, deformation in wheel tracks, and water damage. The material is produced from the fusion of styrene-butadiene-styrene granules, SBS, in a petroleum-based asphalt binder, which is then mixed with heated aggregates, such as stones and sand.
From this model already used on local highways, the question arose that guided the new research: whether discarded plastics could be incorporated into the pavement as a more ecologically appropriate disposal method.
From this, the Hawaii Department of Transportation sought environmental chemist Jennifer Lynch, director and team leader at the Marine Debris Research Center, to investigate how these pavements would behave and whether they could release microplastics into the environment.
Fishing nets and plastic waste enter the project
The state agency made two central requests to the team led by Lynch. The first was to provide abandoned fishing nets, removed from the marine environment of Hawaii, for the creation of asphalt pavements with recycled plastic.
According to Lynch, plastic fishing gear abandoned by foreigners is among the main contributors to the marine debris problem in Hawaii. She states that, so far, the center’s Bounty Project, which pays financial rewards to licensed commercial fishermen for removing this material, has already removed 84 tons of large abandoned fishing gear from the Pacific Ocean.
The second request from the Department of Transportation was to measure the potential release of microplastics in pavements made with plastic waste, compared to the release observed in conventional pavements modified with SBS. Lynch highlighted that the center’s laboratory has state-of-the-art chemical instrumentation to quantify and characterize microplastics in environmental samples, a capability she describes as particularly relevant given the proposal to transform marine debris into long-term infrastructure products for local use.
After a company based in the United States converted the waste into products compatible with incorporation into asphalt, the Department of Transportation took the experimental mixtures to the state’s streets. Subsequently, a local paving company applied sections of a residential road on the island of Oahu with three types of pavement: one with standard SBS, another with polyethylene repurposed from recycling containers in Honolulu, and a third with polyethylene obtained from fishing nets.
What the tests showed about microplastics
After about 11 months of regular road use by traffic, the team began collecting dust samples from each paved section. The goal was to check for the presence of microplastics that could reach the soil around the road.
The researchers processed this material with a method capable of separating different types of polymers from other components present in the road dust, including microplastics, larger plastic fragments, and tire rubber. They then used pyrolysis gas chromatography coupled with mass spectrometry, the Py-GC-MS technique, to identify and quantify the origin of the polymers found.
With this, it was possible to distinguish styrene and butadiene associated with standard PMA, polyethylene from plastic waste and fishing nets, as well as isoprene and butadiene rubber from tires.
The initial tests indicated that pavements with recycled polyethylene did not release more polymers than the control pavement made with SBS.
According to the team, this finding appeared both in mechanical performance tests conducted with pavement samples and in simulations of rainwater collected from the experimental road sections. Although microplastic-sized particles were detected, very few of them were specifically identified as polyethylene, regardless of the type of pavement analyzed.
The researchers point out that this likely occurs because the polymers remain fused in the asphalt binder. Thus, the particles that detach would not be composed solely of plastic, but rather a combination of rock, binder, and fused polymer chains.
Tire wear dominated the observed signals
In addition to comparing the different types of pavement, the center’s team also began to evaluate how much of the polymers present in the road dust came from the asphalt itself and how much was generated by tire wear. In the initial data obtained by Py-GC-MS, the signal from the material released by the tires appeared much more intense than any indication of polyethylene associated with the pavement.
Lynch stated that tire wear overshadowed the polyethylene signal by several orders of magnitude, with peaks much higher than the others. According to her, it was necessary to examine the chromatogram carefully to locate traces of polyethylene among the results.
Although the team emphasizes that more research is still needed to assess the durability of the pavement, the initial results reinforce the possibility of using this material as a destination for plastic waste in the state. The researchers hope that, in the future, the reuse of plastics in paving will help reduce the volume of waste sent to landfills and the sea in Hawaii.
Lynch states that part of society views plastic recycling with skepticism, seeing it as difficult or ineffective. However, she believes that the study shows that recycling can work when sustainability is treated as a priority.
Study available at ACS.
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