In an innovative effort to tackle the problem of plastic waste, Hawaii is implementing a new type of asphalt that incorporates recycled plastics and abandoned fishing nets.
This approach seeks to transform difficult-to-manage waste into useful everyday infrastructure. However, the question arises: could this method release more microplastics into the environment?
After nearly a year of testing on a section of road in Oahu, initial analyses indicate that these mixtures do not emit more polymers than conventional polymer-modified asphalt.
Interestingly, the largest contributor to dust pollution on roads comes from tire wear, redirecting the focus of the study.
The project was commissioned by the Hawaii Department of Transportation with the aim of finding a local solution for the constant flow of plastics, in addition to evaluating its environmental impact.
Hawaii achieves sustainable asphalt
Roads have been paved since 2020 primarily with asphalt modified to withstand tropical weather conditions. The innovation lies in assessing whether recycled waste can replace part of these polymers without negatively impacting the environment.
Hawaii faces particular challenges with plastic due to its geographical location, which complicates recycling and waste export. Abandoned fishing nets are a significant problem, trapping and destroying marine ecosystems.
Through the Bounty Project of the Center for Marine Debris Research, more than 185,000 pounds of nets have been removed from the ocean, equivalent to about 84 metric tons.
Utilizing these materials in asphalt aims to reduce the need for transportation and minimize the use of options like incineration or landfill.
This approach, however, is only viable if the asphalt does not become a new source of particle pollution.
During the tests, the research team collected dust samples from the road to identify the different types of polymers present.
Using advanced techniques like Py-GC-MS, they differentiated between various compounds, including styrene and butadiene from SBS, as well as polyethylene from waste mixtures and tire rubber.
The results showed that pavements with recycled polyethylene did not release more polymers than those controlled with SBS.
This finding was verified through road dust analysis, mechanical tests, and simulated rainwater.
Some microplastic sized particles were detected, although few were polyethylene. Researchers suggest that the polymer integrates within the asphalt binder, and when it detaches, it does so as a mixture with other materials.
A crucial fact revealed that tire wear significantly overshadows the polyethylene signal, supporting reports from the United Nations Environment Programme on the abundance of these particles as primary microplastics.
Researchers emphasize the need for more studies to verify the pavement’s durability under real conditions, including exposure to sun, salt, and climate variations.
In Europe, the European Environment Agency has observed a 12% increase in microplastic emissions from tire abrasion between 2016 and 2022, highlighting the importance of comprehensive and continuous analysis.
