Researchers from RMIT University have successfully demonstrated that fired-clay brick which incorporates biosolids could be a sustainable solution for both the wastewater treatment and brickmaking industries, according to reports by the institution.
Published recently in the journal Buildings, the research showed how making biosolids bricks only required around half the energy of conventional bricks. As well as being cheaper to produce, biosolids bricks also had a lower thermal conductivity, transferring less heat to potentially give buildings higher environmental performance.
Currently, around 30 per cent of the world’s biosolids are stockpiled or sent to landfill, using up valuable land and potentially emitting greenhouse gases, creating an environmental challenge.
About five million tonnes of the biosolids produced in Australia, New Zealand, the EU, US and Canada currently go to landfill or stockpiles each year. Using a minimum 15 per cent biosolids content in 15 per cent of bricks produced could use up these five million tonnes.
Lead investigator associate professor Abbas Mohajerani said the research sought to tackle two environmental issues – the stockpiles of biosolids and the excavation of soil required for brick production.
“More than three billion cubic metres of clay soil is dug up each year for the global brickmaking industry, to produce about 1.5 trillion bricks,” Mohajerani said.
“Using biosolids in bricks could be the solution to these big environmental challenges. It’s a practical and sustainable proposal for recycling the biosolids currently stockpiled or going to landfill around the globe.”
The research examined the physical, chemical and mechanical properties of fired-clay bricks incorporating different proportions of biosolids, from 10 to 25 per cent.
The biosolid-enhanced bricks passed compressive strength tests and analysis demonstrated heavy metals are largely trapped within the brick. Biosolids can have significantly different chemical characteristics, so the researchers recommend further testing before large-scale production.
The research also showed brick firing energy demand was cut by up to 48.6 per cent for bricks incorporating 25 per cent biosolids. This is due to the organic content of the biosolids and could considerably reduce the carbon footprint of brick manufacturing companies.
The results of a comparative Life Cycle Assessment and an emissions study conducted as part of the research confirmed biosolids bricks offered a sustainable alternative approach to addressing the environmental impacts of biosolids management and brick manufacturing.