Oil Shale is Estonia’s prime mineral resource. Oil shale is deposited in a single economic layer with thickness of 2,5 to 3 meters in depth of 7 to 100 meters in area of 2700 km2. Its production makes 70 percent of world’s oil shale production and two thirds of Estonia’s total mineral production. Mining activity started in 1916, peaked in 1980 and is ending in next 30 years. Therefore it is important to save oil shale mining history in easily accessible database. The Mining Institute of Tallinn Technical University has created geographically referenced database of oil shale. MapInfo Professional is used for mapping geology and mining situation. The map includes research and mining fields, mineral and overburden properties, underground and surface workings. Additionally technological diagrams and data are saved. For analysing underground mining influences, exact current mining situation and previous situation is compared with surface topology in mined out areas. Open cast mining results are compared with aerial photos and digital base maps.
Both underground and surface oil shale mining started by handwork. Analyses show that mining influence to the environment from this period has been minimum. As technology developed and political situation changed, the influence increased with raise of production capacity. The conditions for starting of oil shale mining and promoting of development were the war time fuel crisis, the lack of fuel mineral deposits, particularly of oil deposits environs, the interest for fuels by Russia and Germany, particularly for navy, good mining conditions and high quality of the oil shale, disengaged labour. The favourable reasons for liquidating mining activities in Estonia are elimination of interests of great powers, discovering of new oil and gas deposits elsewhere and the development of transportation of fuel minerals, deterioration of mining conditions, exhausting of best reserves and environmental reasons.
The reason for oil shale exploitation in the area of former Russia was the crisis of fuel consumption in the time of World War I. At the beginning oil shale was used as a local fuel. It displaced coal in heating plants, locomotives, cement and lime furnaces. Oil shale mining began in Estonia province in 1916 for supplying Russian capital Petrograd (now St Petersburg).
First period. Permanent kukersite mining started as soon as Estonia got its sovereignty in 1918. One of the oldest oil shale enterprises, State Oil Shale Industry, was established. The private companies formed almost at the same time and were owned by Estonian, as well as by German, English, Swedish and Danish owners.
First fifteen years, all mines used strait works technology, which meant handwork. First stripping shovels and locomotives appeared in thirties. At the same time electric drilling began. Transition to the mechanized mining began in fifties. After that, longwall mining, which was widely used by Russian coal mining, was applied. For oil shale mining, double unit face method was used. Mines applied cutters, conveyors, electric locomotives and force ventilators. In all of the mines electrification was started.
Second period. The technologies of oil shale retorting that were used elsewhere in the world, failed because of local oil shale properties and partly because of economic reasons. In Estonia reliable, inexpensive and productive technology for shale oil retorting was worked out at the beginning of thirties, during The First Estonian Republic. Since 1937 shale oil export value exceeded import value of other fuels. So Estonia achieved the independence in power what was the result of the government policy. The arrangements made by the government for oil shale industry were high depreciation rate, such as 20 per cent, relief inventory from import tax and great export subsidy. This launched the progress of shale oil industry in the Baltic Basin. Oil shale processing products became some of Estonia’s essential export items. Forty five per cent of it was exported in 1938. The oil shale products and shale oil accounted for eight per cent of Estonian export.
Oil shale petrol was also produced, in 1938 only 6.4 per cent of that were exported that formed 1.6 per cent in 1939 of total Estonian export. The cement industry started using oil shale to improve the quality and economy of cement production. Thanks to oil shale, Estonia became independent of foreign fuel and energy.
By 1940, eleven million tons of oil shale had been mined out and he annual production reached 1.7 million tons. After the World War II, the soviet authorities immediately started to develop shale oil processing, mostly for the Baltic Sea Navy and gas generation for the city of Leningrad. The central station electric power industry started to develop in Estonia in the 1950s. Several new mines were constructed and put into operation, in 1950, the annual oil shale output was three and half million tons, and by 1955 it reached seven million tons. The oil shale was used mainly as fuel at Tallinn, Kohtla Järve and Ahtme power stations, at Kohtla Järve and Kiviõli chemical plants and at Kunda Cement Plant.
Third period. Building and putting into operation new power stations (Baltic Thermal Power Station in 1965, output 1400 MW, and Estonian Thermal Power Station in 1973, output 1600 MW) increased remarkably the demand for oil shale. To meet these needs, two new mines and three open casts were opened. At the same time four mines were abandoned. The increase of mining capacity was rapid, from 9.2 million tons in 1960 to 17.5 million tons in 1970. Oil shale mining production reached its maximum level of 31.35 million tons in 1980. Building of the third thermal power station was planned as well and due to this the annual output of oil shale mining was planned to be 50 million tons.
Forth period. In 1981, Nuclear Power Station was built in Leningrad province, which caused the decrease in electricity demand in the north-western part of the former USSR. This led to the decrease of oil shale production in Estonia, 29.7 million tons in 1980, 25.7 million tons in 1985, 21.2 million tons in 1990 and 12.1million tons in 1995. Prof. Reinsalu published the first scientific prognoses of the inescapable decrease in oil shale mining in 1988. According to this, the Estonian oil shale industry would vanish in the third decade of the next century. Since the beginning of the 1990s, the consumption and export of electricity had dropped in Estonia, as it has been in all East European countries. Oil shale output decreased slowly and is now at a level of 10 to 12 million tons in a year.
Ingo Valgma, M.Sc., PhD student
The Mining Institute of Tallinn Technical University, Kopli 82, Tallinn,