He Aznalcóllar spill (Seville), which will be 22 years old on April 25, is one of the largest mining accidents in the world. The fracture of a pond spilled 4.5 million cubic meters of toxic sludge over some 5,000 hectares of agricultural soil, the area equivalent to almost four times the city of Cádiz. A study of the Universities of Granada and Almería revealed that, despite the regeneration work and after more than two decades, a part of the affected area (a 7%), the closest to the mine, maintains high levels of acidity and heavy metals such as arsenic, lead, copper and zinc. Recent research by the universities of Granada, Elche and Tokyo has discovered a weapon against this pollution: the use of compost generated with worms, organic and inorganic waste as well as microorganisms so that the land itself regenerates. It is a kind of immunotherapy applied to the earth.
