Mining operations are a cause of soil degradation. They are associated with a legacy of abandoned metalliferous mine wastes and acid mine drainage, which contributes to around 2% of soil contamination in Europe. 

There is therefore an urgent need for sustainable site re-development strategies and remediation technologies that are effective, both in decontaminating and in preserving soil functions, at affordable costs. 

Low-cost technologies for the recovery of degraded mining areas increasingly use ash from combustion processes as a resource for the remediation of contaminated soils. A total of 175 degraded mining areas (including 114 metallic sulphide mines) were identified throughout Portugal. 

There is also between 150 000 and 200 000 tonnes of biomass ash generated annually in the country that is typically disposed of in landfills, which could be used to help recover degraded soils in former mining areas.