-Oil shale mining is a crucially important industry for the Estonian economy. More than 85 percent of electricity in Estonia is produced from oil shale. The oil shale deposit is located in North-East Estonia. The oil shale bed descends three meters per kilometer to the south. The oil shale seam contains interlayered limestone. Some of it is used as low class aggregate rock and the rest is waste rock which is stored in waste rock heaps. Crushing, separating and sampling tests of the waste material are currently being carried out. Initial results show some developments of cutting and crushing possibilities. The aim of this study is to find technological solutions to oil shale waste rock reuse and improve current mining technology.

Oil shale utilisation losses reach 70% in some cases. These are closely related to legislation, backfilling and waste rock usage. Much smaller sections include production of oil, electricity and chemicals in which most of the research and development is performed today. Current urgent topics for investigating, testing and developing of oil shale mining related questions are backfilling, mechanical extracting of shale, fine separation, selective separation and optimised drilling and blasting. Reducing oil shale losses will be more actual in the future, because the depth of mining increases and the taxes for resource and pollutants are increasing as well.

Mining waste reduction methods include all mining processes beginning from resource distribution until final products in the plant. For comparing and testing possibilities of mine waste reduction, a cooperation project has been set up aiming to create a transnational network with regional networks. The activities carried out on the regional and transnational level will secure better access to knowledge, state-of-the-art technologies and good practice. The study addresses all the waste management challenges and opportunities facing the Baltic Sea Region mining industry, which should be understood as extending to all forms of extraction of natural non-renewable resources. In addition to the main mineral resource, oil shale, there are sufficient reserves of limestone and dolostone, peat, sand, gravel and clay. Phosphorite and granite are considered as occurrences in today's economic situation, in spite of the fact that phosphorite has been extracted for 70 years in the past. All previous mining activities have produced mining waste, e.g. the total volume of waste rock from Estonian oil shale mining is more than 76 million m3 and covers about 790 ha [31] [32] [33] [34]. From an environmental point of view Estonia is in good position, not having acidic reactions and having neutralising alkaline limestone present in all mining areas. Thanks to this, reclamation is easily done with the help of the same mining equipment. Water is purified in settling ponds and does not require additional chemical treatment. For underground mining, the main concern is the stability of the room and pillar mining area [35] [37]. Similar problems are found in Sweden and Finland. In Sweden, there are several old deposits from shale mining, the largest one (Kvarntorp) contains some 40 million m3 of crushed processed black shales and contains several metals of potential value.