It is estimated humans create over 380 million tons of plastic every year, with up to 50 per cent for single-use purposes.
Concurrently, construction around the world continues at a frantic pace.
Wouldn’t it be great if plastic waste could somehow join with construction and together reduce the amount of materials headed to dump sites or the oceans?
That is already happening.
A 2023 study reviewed over 100 articles outlining the efforts made from 1992 to 2022 by businesses, materials scientists, institutions and other interested stakeholders to include plastic waste into building materials and infrastructure.
The U.S.-based authors write nearly two-thirds of the articles were positive, supporting a reasonable end-of-life scenario for plastic waste in end use purposes such as composite asphalt-plastic roads, plastic-concrete, plastic lumber, plastic acoustic/thermal insulation and plastic soil reinforcement/stabilizers. These articles also spoke of the positive social, environmental and human health impacts.
However, the study also points out the remaining one-third of viewpoints were either neutral or negative, with serious doubts expressed about recycled plastics in construction materials. Some called the recycling promotional efforts “greenwashing” which could, “delay and distract from finding real solutions to the plastic pollution crisis.”
Not surprisingly, the American Chemistry Council, a petrochemical industry trade group, is very favourable to the overall use of plastics in construction and infrastructure.
“Plastic makers will play an integral role in rebuilding our nation’s ability to move people, energy, goods and water while simultaneously driving down greenhouse gas emissions.”
However, lead study author Erica Cirino writes what has been overlooked is the fact the processing and reuse of plastic can result in the production of microplastics and nanoplastics.
These tiny fragments of plastic could flake off or leach from plastic-infused construction materials, potentially finding their way into nearby waterways, thus posing environmental risks of their own.
In the concluding remarks, the study’s authors sound unconvinced about the overall environmental benefits.
“Ultimately downcycling plastic waste into construction materials is not circular and does not address the core problem of plastic pollution. While LCAs (Life Cycle Analysis) may deem this to be a next-best approach to addressing plastic waste, current research does not fully assess and weigh potential consequences.”
In other words, more work needs to be done on the research side.
It’s an argument supported in another 2023 study titled Recycled Plastics in Infrastructure, authored jointly by academics and stakeholders associated with construction and engineering. They are looking to the U.S. government for leadership.
Among their recommendations are that the U.S. Environmental Protection Agency (USEPA) should, “support the research and data collection that will be required to understand and evaluate each use’s potential environmental, human health, economic and performance implications.”
In terms of new technologies that might incorporate waste plastic, they suggest the USEPA, “take steps to encourage and facilitate more collaboration among plastics manufacturers, suppliers, recyclers, industrial and infrastructure users.”
In fact, collaboration and testing is already happening in Canada.
The Northern Alberta Institute of Technology (NAIT) is partnering with Heartland Polymers, Inter Pipeline’s polypropylene brand, on a $10-million, 10-year effort to advance the reuse and recycling of plastic in Canada and around the world.
One project is working towards the identification of, “an optimum composition of recycled plastics materials to develop a first-of-its-kind plastic sheet prototype to be used as concrete formwork in the construction industry,” NAIT says.
Field tests are underway in co-ordination with Edmonton-based Clark Builders.
Roads have long been considered a prime use of recycled plastics. Another NAIT-Inter Pipeline project involves the testing and validation of using post-consumer plastics as an additive for asphalt road surfaces.
The four field tests currently underway have alone diverted 3.74 tonnes of post-consumer plastic away from landfills, the equivalent of over 410,000 plastic water bottles.
What makes this project unique is that while other plastics-for-road investigations around the world have focussed largely on warmer climatic zones, the NAIT’s road research is examining plastic’s potential within the wide range of conditions prevalent in Alberta.
Research has also suggested that plastics could be used as a way to reduce high exterior wall temperatures caused by UV light.
While rooftops are often made “cooler” through the use of light colours and heat-reflective materials, walls are more challenging. A recent Inside Innovation column looked at zig-zag wall designs as a possible solution.
But now, a recent study suggests common plastics, particularly those incorporating polypropylene, have been found to have properties that can reflect the band of UV light that causes heating. This opens the door to recycled plastics being used to thermoregulate buildings.
The bottom line to all academic and industry sponsored research is that, yes, there is some potential for plastics to find new life in construction materials. However, this potential needs to be measured against the long-term health risks that many experts point to as a concern.
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