When sewage sludge is processed at wastewater treatment plants, the leftover "biosolid" material is generally dried and set aside. While some of it ends up being used as fertilizer, much is often just stockpiled or sent to a landfill. Soon, however, it could find its way into eco-friendly fired-clay building bricks.
Led by Assoc. Prof. Abbas Mohajerani, a team at Australia's RMIT University recently created a number of such bricks, which incorporated from 10 to 25 percent biosolids.
Due to the fact they're more porous than their conventional counterparts, the biosolid bricks were found to have a lower thermal conductivity. This means that if used in the construction of buildings, they would draw less heat away from the interior.
Additionally, thanks to their organic content, bricks made up of 25 percent biosolids required 48.6 percent less firing energy to manufacture. As a result, factories producing them would have a significantly reduced carbon footprint, plus they would have lower power bills.
The RMIT researchers also observed that 43 to 99 percent of heavy metals present in the biosolids were trapped within the bricks, keeping them from entering the environment – concentrations of heavy metals that did leach out of the bricks were said to be insignificant. Mohajerani previously developed bricks containing cigarette butts, to keep pollutants in them safely contained.
As an added bonus, utilizing biosolids in bricks on a commercial scale would reduce the need to mine clay for brick-making purposes. It should be noted, however, that the chemical content of biosolids can vary significantly. With this in mind, the university states that further testing will be required before large-scale production can begin. That said, the bricks do already pass compressive strength tests.
A paper on the research was recently published in the journal Buildings.
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