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The ash of incinerated sewage sludge can be made into synthetic stone, says
Tsukishima Kikai Company of Tokyo. The ash is blended with up to 20 per cent
silica, alumina and lime, and then mixed and degassed at 1200 to 1300 °C to
produce glass-like stones. Subsequent reheating converts the material to
Ecorock, a building material that can withstand up to 4.5 times as much bending
force as granite or marble. The company is building a $25 million plant
at Suwa to make Ecorock commercially.