Australia’s Department of Urban Services is patenting (WO 97/10190) a method
of using earthworms to clean up sewage and waste contaminated with heavy
metals.
The waste is mixed with paper or cardboard, shredded and aerated, producing
bacteria which the worms like to eat. The dining worms absorb the heavy metals
and excrete acidic castings that have cadmium levels a third lower than the
original waste.
The acidic mix of soil and castings can be neutralised with lime and water,
precipitating the remaining poisons. Dried castings are made into fertilising
pellets for farmland.
