Background Ida-Virumaa, the most north eastern county of Estonia, has large-scale oil-shale processing industries (> 10 million tonnes/year) and, as a result, suffers from a depletion of oxygen. The coking of oil-shale by the companies Viru Keemia Grupp and Kiviõli Keemiatööstuse OÜ leads to the production of oil, and harmful solid waste (semicoke). Currently, the waste is stored in hills situated nearby the enterprises (the amount of semi-coke in these hills is approximately 85 million tonnes, and is increasing by 1 million tonnes annually). Semi-coke is an extremely alkaline (pH = 12,8), porous substance, containing toxic sulphides, phenols, polycyclic aromatic hydrocarbons and other harmful components. On the other hand, non-stabilized slurry is a point source of water pollution, whereas semi-coke, pre-treated with peat, is an excellent absorber and stabilizer of slurry, having the ability to stop odour emission. The “HASCO” project aims to stop, or reduce considerably, the pollution in Ida-Virumaa and return the damaged or poor soils to efficient use. Solving the environmental problems in this area which has one of the highest unemployment rates in Estonia will encourage a positive attitude among the local population. Objectives In general terms, the project will lead to an improvement of the environmental situation of Ida-Viru County and considerably reduce pollution into the Baltic Sea. It will allow for atmosphere CO2 binding and a decrease in greenhouse gas emissions. The recycling of oil-shale processing solid waste will lead to the development of an environmentally friendly by-product – an organic fertilizer to stabilize polluting slurry. Soils damaged by the oil-shale industry will be restored and subsequently planted with hybrid aspen. Existing jobs will be maintained and new jobs will be created. Demonstration pilot areas proving the efficiency of the utilisation of the recycled toxic semi-coke and slurry to restore damaged soils will be set up. Results The project was terminated in May 2005.