Photo: JJ Harrison
Carbon Fiber Paves a Way to Clean Water
Limitations of Permeable Pavement
Impermeable surfaces in the Puget Sound region are almost entirely human-made: roads, parking lots, sidewalks and rooftops. When rain falls on impermeable pavement, all the pollutants pool together – oils from cars, pet waste, pesticides, lawn fertilizer and myriad of other toxins. They then drain into nearby streams, rivers and estuaries creating stormwater that kills wildlife and endangers waterways.
In contrast, permeable pavement made from porous concrete allows rain water to soak into the soil rather than run off the surface. In most cases the soil can act as a natural filter, breaking down and removing pathogens and pollutants.
Permeable materials for roads, paths, sidewalks and parking lots have advanced greatly in recent years and have been used as a key component in the LEED rating system. But because they are highly porous, they are not as durable as traditional concrete and considered too soft for use on high-traffic major roads.
Developing a high strength permeable pavement could greatly expand its use and potential for mitigating stormwater pollution.
Upgrading with Recycled Carbon Fiber
The same light-weight carbon fiber that is boosting the efficiency of Boeing aircraft may also help clean the groundwater back on earth. Boeing, Washington State University (WSU) and the Washington Stormwater Center collaborated to research the use of recycled carbon fiber composites to strengthen permeable pavement, a porous paving material that can reduce stormwater runoff and pollution.
The project took a two-pronged approach to improving permeable pavement. First, the research team recycled carbon fiber composites to strengthen and reinforce porous pavement material. Then the team examined the strengthened material for toxicity to validate that the composite material does not add pollutants into the soil or impact water quality.
The WSU researchers have shown they can greatly strengthen permeable pavements by adding carbon fiber composite material and it actually helps filter stormwater toxins.
Multiple Environmental Benefits
While they have shown the material works at the laboratory scale, the researchers are now conducting real-world tests on pavement applications.
In 2019, with support from Boeing and the Washington State Department of Ecology, the City of Tacoma launched a permeable pavement pilot project. The project is field testing five permeable pavement compositions including pavement made with excess carbon fiber composite supplied by Boeing. WSU researchers will study the compositions for durability and effectiveness at filtering out groundwater pollutants.
The pilot project will help determine the future of a carbon fiber composition and its potential for multiple environmental benefits:
- Reduction in stormwater runoff. Strength provided by carbon fiber has the potential to greatly reduce stormwater by expanding the use of permeable pavement to high-traffic roadways.
- Reduction of stormwater toxins. Laboratory tests show the addition of carbon fiber reduces the toxicity of stormwater, supporting the natural filtering by soil.
- Recycle excess carbon fiber. Carbon-fiber-infused pavement represents another innovation that can help grow the recycling industry for excess carbon fiber composite.
The Boeing Company
Washington State University
Impermeability by the numbers
- The Nature Conservancy 2019 land-cover map reveals 359,500 acres of impermeable surface in the Puget Sound region, or about 560 square miles. That’s over 272,300 football fields of asphalt, concrete and metal where rainwater cannot seep into the ground.
- A single acre of impermeable surface in the Puget Sound region results in 1 million gallons of stormwater runoff annually.