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Turning sewage into structures with biosolid bricks

Associate Professor Abbas Mohajerani with a biosolid brick - a sustainable solution for the wastewater treatment and brickmaking industries.

New research has found a way of turning biosolids from sewage into cheaper, higher performing bricks suitable for the construction industry.

A research team from RMIT University has developed a fired-clay brick as a sustainable solution for the wastewater treatment and brickmaking industries.

The bricks are made up of biosolids, a by-product of the wastewater treatment process, and were found to have a lower thermal conductivity than other bricks, meaning they will transfer less heat and potentially give buildings higher environmental performance.

The research examined the physical, chemical and mechanical properties of fired-clay bricks incorporating different proportions of biosolids, from 10 to 25 per cent.

Researchers found brick firing energy demand was cut almost in half for bricks that incorporated 25 per cent biosolids, due to the organic content and could considerably reduce the carbon footprint of brick manufacturing companies.

Fired-clay bricks incorporating biosolids require around half the energy of conventional bricks and have lower thermal conductivity, potentially giving buildings higher environmental performance.
Fired-clay bricks incorporating biosolids require around half the energy of conventional bricks and have lower thermal conductivity, potentially giving buildings higher environmental performance. Image Credit: RMIT University

Around five million tonnes of the biosolids in Australia, New Zealand, the EU, US and Canada currently go to landfill or stockpiles each year. By using a minimum of 15 per cent biosolids content in 15 per cent of the bricks produced, the research team estimates around five million tonnes could instead be used for construction.

The bricks have 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.

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.

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“More than 3 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,” he said.

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.

The research, funded by RMIT University, Melbourne Water and Australian Government Research Training Program scholarships, is published in the “Green Building Materials Special Issue” of Buildings.