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 Oà leads to the production of oil, and harmful solid waste (semicoke). C ...