After sewage sludge is processed at wastewater treatment plants, a leftover “biosolid” material is generally dried and set aside, often then used as fertilizer, stockpiled, or sent to landfill. A team at Australia’s RMIT University, led by Assoc. Prof. Abbas Mohajerani, has recently found a way to turn incorporate this material into eco-friendly fired-clay building bricks.

Containing 10 to 25 per cent of these biosolids, the material is much more porous than their conventional counterparts and therefore have lower thermal conductivity. Used in the construction of buildings, they draw less heat away from the interior.

Thanks to organic content, these bricks require 48.6 per cent less firing energy to manufacture. This has the potential to significantly reduce the carbon footprint of production, with the added benefit of lower energy costs.

RMIT researchers also spotted that 43 to 99 per cent of heavy metals present in the biosolids remain trapped in the bricks. This prevents them from entering the environment. Mohajerani has even created bricks that contain cigarette butts, preventing the pollutants within them from entering the environment.

An additional benefit at a commercial scale is the decreased need to mine clay for brick-making purposes. As of today, the chemical content of biosolids can vary significantly, however, meaning that the university will require further testing before large-scale production can begin. That being said, the bricks have already passed compressive strength tests.