Would You Live In A House Built From Sewage?

These might look like ordinary bricks other than being round, but you really don't want us to put up an image of what they are made from. Mohajerani et al./Buildings

Most people don't take the expression “shitting bricks” literally, but Dr Abbas Mohajerani is an exception. He's developed a technology to make safe, smell-free bricks out of sewage, solving two problems at once. Turns out, to add to the little pigs' houses of straw and wood, we could have made one out of poop.

With more than 7 billion people on the planet, the world produces a lot of waste. After processing in treatment facilities, we're left with what is tactfully known as biosolids. Some biosolids are used to fertilize plants no one will eat, such as timber plantations, but there are concerns about using them on food crops. As a result, about 30 percent of the biosolids in the world are sent to landfill or pile up while we try to find uses for them.

Mohajerani, who works at Australia's RMIT University, fired the biosolids into bricks and found that if you can get over the yuck factor, they have some major advantages over traditional clay.

“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 in a statement

Brick production requires a lot of heat, and the fuel required makes it a significant contributor to global warming. Depending on location, the pits from which the brick clay is dug can be local environmental menaces, and transporting bricks to places that lack suitable clays comes with its own environmental footprint.

Mohajerani wondered if the 9 million tonnes of biosolids produced in the EU, or 7 million from the US each year, could be turned to bricks, removing the problem of biosolid disposal and reducing issues with existing brick manufacturing. He combined traditional brick materials with biosolids to produce bricks that were 10, 15, 20, and 25 percent biosolid and tested the performance of each.

In the peer-reviewed journal Buildings, Mohajerani announced his work was more successful than anyone might have expected. For one thing, it requires almost half as much energy to fire a 25 percent biosolid brick as a conventional one. Better still, the partially biosolid bricks are more porous and therefore less thermally conductive. Buildings constructed out of them will need less heating and cooling.

Biosolids often contain heavy metals (something you might not want to think about too hard), but Mohajerani found most were immobilized by the firing, so the risk of leaching when it rains is minimal.

If Mohajerani's idea ever takes off in his home city, it could give a whole new meaning to the cult Facebook page Shit Brick Fences Of Melbourne, and make living in a shit house not such a bad thing.

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