Waste materials from the pulp and paper industry look set to be diverted from landfill and repurposed for road construction.
This is the aim of researchers at the University of British Colombia (UBC) Okanagan in Canada, who are particularly focussed on wood-based pulp mill fly ash (PFA), which is a non-hazardous commercial waste product.
The North American pulp and paper industry is said to generate over one million tons of ash annually by burning wood in power boiler units for energy production. When sent to a landfill, the producer pays between $25 to $50 per ton, so mills are looking for alternative usages of these by-products.
“Anytime we can redirect waste to a sustainable alternative, we are heading in the right direction,” said Dr Sumi Siddiqua, associate professor at UBC Okanagan’s School of Engineering and leader of the Advanced Geomaterials Testing Lab, where researchers find different reuse options for industry by-products.
This new research, co-published with postdoctoral research fellow Dr Chinchu Cherian, investigated using untreated PFA as an economically sustainable low-carbon binder for road construction.
“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,” said Dr Cherian. “Through our material characterisation and toxicology analysis, we found further environmental and societal benefits that producing this new material was more energy efficient and produced low-carbon emissions.”
According to Dr Siddiqua, the construction industry is concerned that toxins used in pulp and paper mills may leach out of the reused material.
“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.”
Dr Cherian said further research is required to establish guidelines for PFA modifications to ensure its consistency, but she is confident their research is on the right track.
“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,” she said. “And not just benefits for the industry, but to society as a whole by reducing waste going to landfills and reducing our ecological footprints.”
The research has been published in the Journal of Cleaner Production.