Waste materials from the pulp and paper industry have long been considered a possible filler for construction products such as cement, but over the years these materials have ended up in landfills. Researchers at UBC Okanagan are now developing guidelines for using this waste to build roads in an environmentally friendly way.
The researchers were particularly interested in wood-based cellulose fly ash, which is a non-hazardous commercial waste product. The North American pulp and paper industry generates more than a million tons of ash annually by burning wood in energy boiler units for energy production. When shipped to landfill, the producer bears a cost of about $ 25 to $ 50 per tonne, so mills are looking for an alternative use of these by-products.
“Whenever we can redirect waste to a sustainable alternative, we go in the right direction,” says Dr. Sumi Siddiqua, Associate Professor at UBC Okanagan School of Engineering. Dr. Siddiqua runs the Advanced Geomaterials Testing Laboratory, where researchers are discovering various possibilities for reusing by-products in industry.
This new research was published in collaboration with postdoctoral researcher dr. Chinchu Cherianom investigated the use of untreated PFA as an economically viable low-carbon binder for road construction.
“The porous nature of PFA acts like a pass for the stickiness of other materials in cement that allows the entire structure to be stronger and more elastic than materials not made of PFA,” says Dr. Cherian. “Through our material characterization and toxicological analysis, we have discovered further environmental and social benefits that the production of this new material is more energy efficient and has produced low carbon emissions.”
But dr. Siddiqua notes that the construction industry is concerned that toxins used in pulp and paper plants could leak from reuse of the material.
“Our findings indicate that the cement bonds developed using untreated PFA are so strong that little or no chemical is released. It can therefore be considered a safe raw material for environmental use.”
Although dr. Cherian explains that further research is needed to establish guidelines for PFA modifications to ensure its consistency, she is convinced their research is on the right track.
“Overall, our research confirms that the use of recycled wood ash from pulp mills for construction activities such as making sustainable roads and cost-neutral buildings can bring huge environmental and economic benefits,” she says. “And not only benefits for the industry, but for society as a whole by reducing waste going to landfills and reducing our environmental footprints.”
Meanwhile, while cement manufacturers may begin to incorporate PFA into their products, Dr. Cherian says we should continuously test and evaluate the properties of PFA to ensure overall quality.
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Material provided Campus of the University of British Columbia in Okanagan. Note: Content can be edited for style and length.