In an effort to create a more circular economy of materials, researchers from UBC Okanagan are designing methods to recycle waste from pulp mills as a binder to be utilized in road construction. The study zones in on the possibility of using the non-hazardous wood-based pulp mill fly ash (PFA) to produce cement, thereby keeping the waste out of landfills while simultaneously promoting more sustainable roads.
"Anytime we can redirect waste to a sustainable alternative, we are heading in the right direction," says Dr. Sumi Siddiqua, associate professor at UBC Okanagan's School of Engineering who leads the Advanced Geomaterials Testing Lab. Dr. Siddqua’s collaboration on the project with postdoc Dr. Chinchu Cherian was published in the Journal of Cleaner Production.
This research aims to address concerns from the pulp and paper industry about landfill costs. Pulp and paper mills must spend between $25-50 per ton to send PFA to a landfill. With the North American industry generating over a million tons of ash every year, that starts to add up.
"Overall, our research affirms the use of recycled wood ash from pulp mills for construction activities such as making sustainable roads and cost-neutral buildings can derive enormous environmental and economic benefits," comments Dr. Cherian. "And not just benefits for the industry, but to society as a whole by reducing waste going to landfills and reducing our ecological footprints."
Dr. Cherian also says that adding PFA to cement makes the cement itself stronger. "The porous nature of PFA acts like a gateway for the adhesiveness of the other materials in the cement that enables the overall structure to be stronger and more resilient than materials not made with PFA. Through our material characterization and toxicology analysis, we found further environmental and societal benefits that producing this new material was more energy efficient and produced low-carbon emissions."
Although more research will be needed to ensure that toxins from the PFA don’t leach out of the cement, the researchers note: "Our findings indicate because the cementation bonds developed through the use of the untreated PFA are so strong, little to no release of chemicals is apparent. Therefore, it can be considered as a safe raw material for environmental applications."