COUNTRIES running short of landfill space could soon be using sewage to build homes for their citizens instead of dumping it. A team in Taiwan has found that sludge from sewage works can be used to bulk up ordinary house bricks.
鈥淚t鈥檚 a win-win situation because it converts the wastes into useful materials and alleviates disposal problems,鈥� says Chih-Huang Weng, leader of the team at I-Shou University in Kaohsiung County that devised the process.
The impetus behind the idea was to find new uses for the 670,000 tonnes of sewage sludge the island produces each year, and for which landfill space is fast running out. Although the solids Weng and his team added to the bricks were filtered from industrial effluent, he says domestic sewage would do just as well.
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In a paper accepted for publication in Advances in Environmental Research, Weng鈥檚 team report achieving their best results when sewage sludge accounted for 10 per cent of the material in clay bricks fired at about 900 掳C. But the process worked even when the 鈥渂iobricks鈥� contained as much as 30 per cent sludge.
As well as getting rid of the sludge, there are other benefits. The firing process locks away for good any toxic heavy metals in the sludge, and also destroys any hazardous microbes and organic material. And the bricks don鈥檛 smell at all, says Weng.
But Weng admits that people might need a little convincing to live in such intimate contact with their own waste. 鈥淟egal approval and public acceptance鈥� remain to be sought, he says.
While agreeing that such a use of the sludge benefits the environment, John Hobson, an expert in effluent treatment at Britain鈥檚 Water Research Centre in Medmenham, Buckinghamshire, says that brick makers might need to be assured that there is nothing about the process that would alter the colour or durability of bricks that might put potential customers off. He also says such bricks might need to meet additional standards to guarantee they don鈥檛 pose new health hazards.