Tackling plastic pollution with recycled plastic waste solutions
The United States’ most exotic state, Hawaii, faces a growing problem with plastic pollution. Its ocean waters are plagued by marine debris, primarily stemming from household plastic waste from the archipelago’s various islands and discarded fishing nets. In short, no place on Earth is immune to plastic, as recent research has also highlighted in the Fiji Islands. To grasp the extent of the issue, the Bounty Project, which offers an economic incentive to authorized fishermen for marine waste removal, has removed 84 tons of large abandoned fishing gear from the Pacific Ocean.
From Hawaii, a research group has tested a new method to recycle plastic and transform it into asphalt for the island’s roads. “By reusing existing plastic waste in Hawaii, we can reduce the environmental and economic impact of transporting plastic waste from the islands, incinerating it, or disposing of it in Hawaii’s overflowing landfills,” explains Jeremy Axworthy, a researcher at the Center for Marine Debris Research at Hawaii Pacific University.
Testing recycled plastic waste in road asphalt
In fact, since 2020, Hawaii’s roads have been paved with a type of polymer-modified asphalt to increase its strength and durability. In 2022, the Hawaii Department of Transportation launched a significant test on Fort Weaver Road; instead of using 100% traditional bitumen, they utilized a mix containing post-consumer recycled plastic. The goal was to verify if it reduced pothole and crack formation compared to standard asphalt, extending the road’s lifespan. Indeed, this new research has led to a type of asphalt – produced by melting styrene-butadiene-styrene granules into a petroleum-based bituminous binder – that is more resistant to cracks, ruts, and water damage, qualities particularly important for the state’s tropical climate.
Plastic improves asphalt durability
The addition of plastic to asphalt would not only allow for a new circular life for waste but also enable improved chemical properties of the road surface. Furthermore, plastic helps asphalt to flex slightly under the weight of vehicles without breaking, and plastic roads tend to withstand the high surface temperatures typical of tropical climates better. Despite researchers’ enthusiasm, another critical aspect is also being monitored: microplastics. The main concern is resilience to wear over time, as there’s a risk that the road could still release tiny plastic fragments into the environment and thus into the ocean.
Current tests are precisely designed to understand if the polymer remains stable within the bitumen or if it becomes a secondary pollutant. Meanwhile, a local paving company has already constructed sections of a residential road on Oahu island with asphalt containing standard SBS, recycled polyethylene from Honolulu’s recycling bins, and polyethylene derived from fishing nets. After nearly a year of use, the team collected road dust samples from each paved section to check for any release of microplastics, which could have contaminated the surrounding soil. However, further research is needed to assess the durability of the pavement.