Plastic from the ocean turned into roads? Hawaii is testing a surprising idea

An ambitious project by engineers working in Hawaii shows that environmental pollution can be reduced in ways that also benefit the economy, and that no material has to go to waste. The new concept aims to ease the burden on the oceans while reducing the pressure on increasingly overcrowded landfills.

Plastic waste is flooding the islands

The problem of plastic waste accumulating in the oceans and washing up on popular beaches is not unique to Hawaii. An increasing number of island nations are reporting growing marine litter, and in many cases the pollution is imported. Ocean currents carry bottles, packaging and abandoned fishing nets across thousands of kilometres.

Local communities, tourists and, above all, marine wildlife are suffering. Animals become entangled in plastic bags and ropes, and often ingest both large and tiny pieces of plastic, putting their health and survival at risk. Plastic debris also accumulates on coral reefs, blocking sunlight and transporting harmful disease-causing pathogens. The problem continues to grow as plastic breaks down into smaller fragments, spreading even deeper and farther throughout the environment.

Asphalt made from ocean plastic

For the past six years, roads in Hawaii have been built using polymer-modified asphalt (PMA), which is more durable and resilient than conventional paving materials. Researchers at Hawaiʻi Pacific University set out to investigate whether the styrene-butadiene-styrene (SBS) pellets used in its production could be replaced with plastic recovered from the ocean. The research was funded by the Hawaii Department of Transportation.

The experiment used discarded fishing nets collected from the coastal waters surrounding the Hawaiian archipelago. Their availability has recently increased thanks to the Bounty Project, which rewards fishers for removing waste from the Pacific Ocean. So far, the initiative has resulted in the recovery of 84 tonnes of marine debris.

The recovered ocean plastic was then processed and incorporated into asphalt production. The resulting material was used to resurface a section of road on the island of Oahu. Most importantly, an analysis conducted after one year of use found that the road released no more microplastics into the environment than the asphalt that had previously been used.

“This work shows that recycling can succeed when society puts sustainability first,” said Jennifer Lynch, head of the research team at the Center for Marine Debris Research at Hawaiʻi Pacific University.

Not the first success in Hawaii

Tonnes of ghost nets recovered from the sea have also supported the development of the Hawaiʻi Nets to Energy Program. For more than 20 years, recovered marine debris has been converted into fuel to power a dedicated energy facility in Honolulu. Estimates suggest that 100 tonnes of plastic waste can generate enough electricity to supply 43 households for an entire year.

The environmental organisation Parley for the Oceans has spent years collecting plastic waste from beaches and recycling it. The processed material is transformed into climbing carabiners, building blocks, jewellery and educational products.

Although this initiative operates on a smaller scale than road construction or asphalt production, its primary goal is to engage and educate local communities. Hawaiian residents can take part in workshops where recycled plastic is turned into practical everyday objects. As a result, cleaning up beaches is taking on an entirely new meaning.