Storage and disposal
Safe temporary storage and safe permanent disposal of mercury and mercury compounds
The safe long-term storage of mercury is regulated by existing EU waste legislation (Directives 2008/98/EC & 1999/31/EC and Decision 2003/33/EC). This ensures that only those sites with the necessary permits for the storage of hazardous waste can be used. In the case of liquid mercury, the permit shall also include requirements for regular visual inspections of the containers and the installation of appropriate vapour detection equipment to detect any leak.
Storage of liquid (metallic) mercury in sealed containers in deep salt mines was originally considered a very safe option for the disposal by hazardous waste experts and established storage company operators. This solution reduces the risk of accidental environmental exposure as the mercury does not need to be moved after it has been stored in a dedicated area. However, the 2017 Mercury Regulation only allows such storage on a temporary basis, for a maximum period of 5 years, with the possibility to extend it by an 3 additional years through a delegated act. After that period, all liquid mercury should be converted into ‘mercury sulphide or a comparable chemical compound which is equally or more stable and equally or less soluble in water and that presents no greater environmental or health hazard than mercury sulphide’.
The mercury sulphide or comparable chemical compound can then be permanently disposed of, respecting the general European hazardous waste rules and some additional provisions specified in the Mercury Regulation (e.g. mercury sulphide can be permanently stored in underground salt mines or hard rock formations; or in solidified form also in above-ground storage).