Oil shale in Estonia

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A brownish-grey wall of kukersite is shown with a blue-handled pick axe somewhat to the right of its centre. Fragments of other rocks are visible; most are a little wider than the pick axe handle.
Outcrop of Ordovician kukersite oil shale, northern Estonia

Oil shale (Estonian: põlevkivi) is a strategic energy resource that constitutes about 4% of Estonia's gross domestic product. In 2012, Estonia's oil shale industry employed 6,500 people – about 1% of the national workforce. Of all the power stations in the world that are fired by oil shale, the two largest are in this country.[1][2] Most mined oil shale is used for electricity generation, accounting for about 85% of Estonia's total electricity production. A smaller proportion of the mined oil shale is used to produce shale oil, a type of synthetic oil extracted from shale by pyrolysis, which is sufficient to keep Estonia as the second largest shale oil producer in the world after China. In addition, oil shale and its products are used for district heating and as a feedstock material for the cement industry.

There are two kinds of oil shale in Estonia, both of which are sedimentary rocks laid down during the Ordovician geologic period.[3] Graptolitic argillite is the larger resource, but, because its organic matter content is relatively low, it is not used industrially. The other one is kukersite, which has been mined for almost a hundred years. Kukersite deposits in Estonia account for 1.1% of global oil shale deposits.

In 1838, an unsuccessful attempt was made to distil oil from oil shale.[4] Modern industrial use of oil shale did not commence until 1916. Production of shale oil began in 1921. Oil shale was first used to generate electrical power in 1924.[5] Shortly thereafter, systematic research into oil shale and its products began, and in 1938 a department of mining was established at Tallinn Technical University. After World War II, Estonian oil shale gas was used in Saint Petersburg (than called Leningrad) and in northern cities in Estonia as a substitute for natural gas. Increased need for electricity in the north-west of the Soviet Union led to the construction of large oil shale-fired power stations. Oil shale extraction peaked in 1980. Subsequently, new nuclear reactors that had come on line in Russia in 1981 reduced demand for electricity produced from oil shale. This reduced demand, followed by a restructuring of the industry, led to a decrease in oil shale mining in the 1980s and 1990s. Mining increased at the beginning of the 21st century.

The industry continues to have a serious impact on the environment. It produces about 70% of Estonia's ordinary waste, 82% of its hazardous waste, and more than 70% of its greenhouse gas emissions. It alteres the water circulation, lowers the groundwater level, and decreases water quality. Former and current oil shale mines cover about one percent of Estonia's territory.


Graptolitic argillite[edit]

Main article: Graptolitic argillite
A specimen of Estonian graptolite argillite. The shiny portions are pyrite.
A specimen of graptolite argillite containing pyrite (FeS2) from the Türisalu cliff, an outcrop of the Türisalu Formation
An isopach map of the Ordovician graptolitic argillite deposits in northern Estonia, indicating thickness in meters

Estonian graptolitic argillite (also known as dictyonema argillite, dictyonema oil shale, dictyonema shale or alum shale) is a marinite-type of black shale.[6][7] Although the name dictyonema argillite is widely used instead of graptolitic argillite, it is now considered a misnomer as the graptolite fossils in the rock, earlier considered dictyonemids, were reclassified during the 1980s as members of the genus Rhabdinopora.[7][8][9]

Graptolitic argillite was formed some 480 million years ago during the Early Ordovician under a marine environment.[10] In mainland Estonia, it occurs at the foot of the North Estonian Klint, ranging from the Pakri Peninsula to Narva in an area covering about 11,000 square kilometres (4,200 sq mi).[10][11] When findings in the western Estonian islands are included, its extent increases to about 12,200 square kilometres (4,700 sq mi).[7] The thickness of the layer varies from less than 0.5 metres (1 ft 8 in) to a maximum of 8 metres (26 ft) in western Estonia, as does its subsurface depth, which ranges from 10 to 90 metres (33 to 295 ft).[11]

The composition of graptolitic argillite varies by location within Estonia. Its organic content ranges from 10 to 20% and its sulfur content from 2 to 4%. Correspondingly, its calorific value is 5–8 megajoules per kilogram (MJ/kg; 1,200–1,900 kcal/kg) and its Fischer Assay oil yield is 3–5%.[11] Graptolitic argillite from the northeastern region contains up to 9% pyrite (generally between 2.4 and 6%), heavy metals such as uranium (up to 1,200 parts per million (ppm) or 300 grammes per tonne (g/t)), molybdenum (up to 1,000 ppm or 600 g/t), vanadium (up to 1,600 ppm or 1,200 g/t), and nickel,[3][7] and other minerals including K-feldspars, quartz, clay minerals, light-brown phosphatic ooids, and accessory amounts of zircon, tourmaline, garnet, rutile, chalcopyrite, and glauconite.[7] Graptolitic argillite from the northwestern region contains fewer metals than are present in deposits in the northeast; it also contains more clay minerals.[3] Rock in these deposits contains corundum, amphiboles, and kyanite.[7]

Geological reserves of graptolitic argillite in Estonia have been estimated at 60–70 billion tonnes.[6][10] Although reserves of graptolitic argillite exceed that of kukersite, attempts to use it as an energy source have been unsuccessful due to its low calorific value and high sulfur content.[3][11][12] However, graptolitic argillite in Estonia contains a potential 2.1 billion tonnes of oil. In addition, it contains 5.67 million tonnes of uranium, which makes it one of the main potential sources of uranium in Europe. The graptolitic argillite also contains 16.53 million tonnes of zinc and 12.76 million tonnes of molybdenum. There is as yet no economical and environmentally friendly technology to extract these metals or the oil.[12]


Main article: Kukersite
A map of kukersite deposits in northern Estonia and Russia. The upper, northern third of the map shows the bordering water bodies. The Baltic Sea lies to the left of centre and the Gulf of Finland to the right.
Location of kukersite deposits within the Baltic Oil Shale Basin in northern Estonia and Russia

Kukersite is a light-brown marine-type Late Ordovician oil shale formed some 460 million years ago.[13] Its name, given by Russian paleobotanist Mikhail Zalessky in 1917, reflects the German name for Kukruse Manor where he obtained oil shale samples.[14][15][16][17]

Kukersite deposits in Estonia are the world's second highest-grade deposits after the Australian torbanite.[18] Its organic content varies from 15% to 55%, averaging over 40%. Correspondingly, its mean calorific value is 15 MJ/kg (3,600 kcal/kg).[18] Conversion ratio of its organic content into usable energy (shale oil and oil shale gas) is between 65 and 67%[18][19] and its Fischer Assay oil yield is 30 to 47%.[20]

The principal organic component of kukersite is telalginite, which originated from the fossil green alga Gloeocapsomorpha prisca. This species of algae has affinities with the extant modern cyanobacterium, Entophysalis major, which forms algal mats in intertidal to very shallow subtidal waters.[20] Matrix minerals include predominantly low-magnesium calcite, dolomite, and siliciclastic minerals. Kukersite's heavy metal content is low in comparison with other oil shales in Estonia and Sweden.[21]

A photograph of northern Estonian kukersite. The rock is chocolate brown and the apparently abstract white branching figures are fossils.
Fossils in northern Estonian kukersite

Kukersite was deposited in a shallow marine basin. It lies at depths of 7 to 170 metres (23 to 558 ft).[11][19] The most significant kukersite deposits in Estonia – the Estonian deposit and the Tapa deposit – cover about 3,000 to 5,000 square kilometres (1,200 to 1,900 sq mi)[11][22][23] and together with the Leningrad deposit, which is an extension of the Estonian deposit, form the Baltic Oil Shale Basin.[24][25] The Estonian deposit, which covers about 2,000 square kilometres (770 sq mi), is used industrially. The Tapa deposit is not accounted as a reserve due to its lower calorific value, which makes its extraction economically inexpedient.[17][26] In northern Estonia there are 50 layers of kukersite; the six lowest of these form a 2.5-to-3-metre (8 ft 2 in to 9 ft 10 in) thick mineable bed.[3] In this area kukersite lies near the surface. To the south and west it lies deeper and its thickness and quality decrease.[26]

According to the International Energy Agency, Estonia's kukersite represents about 1.1% of global and 17% of European oil shale resources.[27] The total kukersite resources in Estonia are estimated to be about 4.8 billion tonnes, including about 1 billion tonnes economically proven reserve, 0.3 billion tonnes economic probable reserve and about 3.5 billion tonnes uneconomical proven and probable reserve.[28][29] The term "active resources" is used to describe the combination of economically proven and probable reserves. It consists of mineable deposits with energy ratings of at least 35 gigajoules per square metre and calorific values of at least 8 MJ/kg, located in areas without environmental restrictions.[26][28][30] Up to 650 million tonnes or 50% of active resources are designated as recoverable.[29]


Early history[edit]

The earliest documented record of oil shale in Estonia, authored by the Baltic German publicist and linguist August Wilhelm Hupel, dates to 1777.[17] According to a 1785 report by German scientist Peter Simon Pallas, 18th-century naturalist and explorer Johann Anton Güldenstädt had in 1725 described a "burning rock" in Jõhvi, but Güldenstädt's published travel notes do not mention the incident.[17][31][32][33] Estonian oil shale, based on samples originating from the Kohala Manor near Rakvere, was first described by Anton-Johann Engelhardt, an official of Tsarist Russia who was responsible for the economy of Livonia.[16][33] The first scientific research into the rock's oil yield, using samples from land belonging to the Vanamõisa and Kohala manors, was carried out at the Russian Academy of Sciences in 1791 by the German chemist Johann Gottlieb Georgi.[17][33] In 1838 and 1839, the Baltic German geologist Gregor von Helmersen published a detailed description of the deposits of kukersite in Vanamõisa and graptolitic argillite in Keila-Joa.[33] In 1838 he made an attempt to distil oil from the Vanamõisa oil shale deposit.[4][34][35]

Due to the large-scale amelioration works and digging of drainage ditches in 1850s, the presence of oil shale was discovered in several locations in Estonia. In 1850–1857, oil shale occurrence was studied by the Baltic German geologist Carl Friedrich Schmidt who introduced the name of Kuckers stage to describe the oil shale containing geological beds exposed in the draining ditch on the territory of Kukruse Manor. The name of kuckers was used in German and Russian literature until the new name of kukersite was adopted in 1917.[36] Russian chemist Aleksandr Shamarin who at the end of the 1860s studied the composition and properties of oil shale originating from the Kukruse area, found it rational to use oil shale for production of gas and as a solid fuel. However, oil shale extraction for oil production was considered unprofitable.[36] During the rest of the nineteenth century oil shale was used locally as a low-grade fuel only.[37] In 1870s, Robert von Toll, owner of the Kukruse Manor, started to use oil shale as a fuel for the manor's distillery.[38]

At the University of Tartu oil shale geology and chemistry analyses were conducted during the nineteenth century by also Georg Paul Alexander Petzholdt, Alexander Gustav von Schrenk, Carl Ernst Heinrich Schmidt, among others.[17][31]

There were failed attempts to use graptolitic argillite as fertilizer in the 19th century. In the beginning of 20th century, geologist and engineer Carl August von Mickwitz studied self-ignition of graptolitic argillite near Paldiski.[39]

Beginning of oil shale industry[edit]

A monument commemorating the beginning of the oil shale industry, consisting of a grey concrete block about 1.5 metres wide and three-quarters of a metre deep. The block is topped by a black metal hopper filled with rocks. A blue plaque with white Estonian-language lettering just above the block explains its significance.
Historical monument at the location where the first tonnes of oil shale were mined in Pavandu, Kohtla-Järve

Analysis of Estonian oil shale resources and mining possibilities intensified during the early 20th century while Estonia was part of the Russian Empire. Industrial development was under way in Saint Petersburg, but regional fuel resources were in short supply. A large shale oil extraction plant for processing Estonian oil shale was proposed in 1910. The outbreak of World War I, coupled with a fuel supply crisis, accelerated the pace of the research.[31]

In June 1916, the Russian geologist Nikolay Pogrebov oversaw mining of the first tonnes of oil shale at Pavandu and delivered it to Saint Petersburg (then Petrograd) Polytechnic Institute for large-scale experiments.[40][41] This is considered the beginning of the Estonian oil shale industry.[8] It happened more than half a century after oil shale industry had emerged in Scotland which had the leading oil shale industry that time, but a decade before it happened in China, which along of Estonia is the other leading oil shale exploiting country nowadays.[42] In total, 640–690 tonnes of oil shale was sent to Saint Petersburg for tests in 1916.[36] Oil shale was tested at the Saint Petersburg Polytechnic Institute's gasworks and was also burned in boiler houses. For large-scale oil shale utilisation, the construction of oil shale-fired power stations and oil shale thermal processing facilities was planned.[5] That same year, two Saint Petersburg's private companies which were established specially for the oil shale mining, Böckel & Co. and Mutschnik & Co., began surface mining at Kukruse and Järve, respectively.[36][43] In the following year both companies terminated their mining activities.[44]

In 1917, the special commissioner of the Russian Provisional Government for oil shale purchasing and stockpiling began preparing an oil shale mine at Pavandu.[44] In February 1918, the area surrounding the oil shale basin in northeast Estonia was occupied by German troops. During the German occupation, mining activities were carried out at Pavandu by the German company Internationales Baukonsortium (English: International Construction Consortium), including sending oil shale to Germany for investigation and experimentation. This work used a retort constructed by Julius Pintsch AG, known as a Pintsch generator. In late 1918, German forces left Estonia, by which time no more than a single trainload of oil shale had been mined and sent to Germany.[45]

Development during Estonia's independence[edit]

 black-and-white photograph, dated 1924, of rail cars approaching a shale oil extraction facility. Small dark squares on the lower right indicate its path under a bridge.
Entrance to the Kukruse oil shale mine (1920s)
A black-and-white photograph of an open-pit shale mine dated to 1933. The upper half of the photo is occupied by a partly cloudy sky. The darker lower half shows a rail line, below ground level, with workers and hoppers full of materials.
Open-pit oil shale mine in Estonia (1933)
A black-and-white photo of the shale oil processing facility at Kohtla-Järve, dated to 1924. A rail line is shown in the lower third of the photo.
Kohtla-Järve shale oil extraction plant (Riigi Põlevkivitööstus, 1924)
A black-and-white photo of a shale oil extraction plant at Kohtla operated by New Consolidated Gold Fields Limited
Kohtla shale oil extraction plant (New Consolidated Gold Fields Ltd., 1931)
A black-and-white photo of the Püssi power station, dated to 1937
Püssi power station (1937)

On 24 November 1918, Riigi Põlevkivitööstus (English: Estonian State Oil Shale Industry) was established as a department of the Ministry for Trade and Industry. The enterprise, later named Esimene Eesti Põlevkivitööstus (English: First Estonian Oil Shale Industry), was the predecessor of Viru Keemia Grupp, one of the current shale oil producers in Estonia. It took over the existing Pavandu open-pit mine.[45] New open-pit mines were opened at Vanamõisa in 1919 and underground mines at Kukruse and Käva in 1920 and 1924 respectively. At the same time, several investors from abroad initiated oil shale enterprises in Estonia. Underground mines were opened at Kohtla (1937), and open-pit mines were opened at Kiviõli (1922; located underground since 1930) Küttejõu (1925), Ubja (1926) and Viivikonna (1936).[5] Initially, oil shale was used primarily in the cement industry, for firing locomotive furnaces, and as a household fuel. The first major industrial consumers of oil shale were the Port Kunda cement factory (now Kunda Nordic Tsement) in Kunda, which as an owner of the Ubja open-pit mine transferred its rotary kilns for cement production to oil shale firing in 1921, and the Asserin portland cement factory in Aseri.[5][46] In 1925, the Tallinn pulp factory Põhja Paberi- ja Puupapivabrik (English: Nordic Paper and Woodboard Mill) acquired the mining company Eesti Küttejõud (English: Estonian Heating Power), which had been established in 1922 by the Union of Estonian Industrialists as the first private oil shale mining company. By 1925, all locomotives in Estonia were powered by oil shale.[47]

Shale oil production started in Estonia in 1921, when Riigi Põlevkivitööstus built 14 experimental oil shale processing retorts in Kohtla-Järve.[5][48] These vertical retorts used the method developed by Julius Pintsch AG that would later evolve into the current Kiviter processing technology. Each retort processed 40 tonnes of oil shale per day and produced an oil yield of 18%.[48] Along with the shale oil extraction plant, an oil shale research laboratory was founded in 1921.[43] In 1924, the British investor-owned Estonian Oil Development Syndicate Ltd. (later Vanamõisa Oilfields Ltd.) purchased an open-pit mine in Vanamõisa and opened a shale oil extraction plant which used horizontal retort (fusion retort) technology.[3][48][49] Each of the plant's two retorts was capable of retorting 15 tonnes of shale per day; however, technical problems arose and the plant was abandoned in 1931.[48][49] The German-owned company Eesti Kiviõli (German: Estländische Steinöl, English: Estonian Stone Oil, predecessor of Kiviõli Keemiatööstus), affiliated with G. Scheel & Co. and Mendelssohn & Co., was established in 1922.[50][51] After unsuccessful tests with the moving grate kiln, the company built four tunnel kilns between 1927 and 1938.[5][51] The Swedish–Norwegian consortium Eestimaa Õlikonsortsium (Swedish: Estländska Oljeskifferkonsortiet; English: Estonian Oil Consortium), controlled by Marcus Wallenberg, was founded in 1926 to build a shale oil extraction plant in Sillamäe.[49][52] The consortium built a tunnel oven in 1928. However, due to recession, production halted in 1930 and was not restarted until 1936.[48][53] A second tunnel oven was added in 1938.[54] In 1936, it produced 15,000 tonnes of oil, including 2,400 tonnes of gasoline.[48] New Consolidated Gold Fields Ltd. of the United Kingdom built a shale oil extraction plant at Kohtla-Nõmme in 1931 that was equipped with eight rotating retorts (Davidson retorts).[5][48] Each of these retorts was capable of processing 15 tonnes of oil shale per day.[48] This facility continued to operate until 1961.[5]

In 1939 Estonia mined 1.453 million tonnes of oil shale and produced 181,000 tonnes of shale oil, including 22,500 tonnes of oil that were suitable gasoline equivalents. The largest shale oil producer was Eesti Kiviõli (70,000 tonnes) followed by Esimene Eesti Põlevkivitööstus (61,000 tonnes). The mining and oil industry employed 6,150 persons.[50] Shale oil and gasoline produced from shale oil were exported to Germany, Czechoslovakia, Finland, Sweden, Norway, Latvia and Lithuania. In 1934, Eesti Kiviõli and New Consolidated Gold Fields established the service station chain Trustivapaa Bensiini (now: Teboil) in Finland. During 1940 this chain sold more shale-oil-derived gasoline in Finland than did the entire conventional gasoline market in Estonia.[55] In 1935, Eesti Kiviõli concluded a contract with the German Kriegsmarine to supply shale oil as a ship fuel.[50][56] Esimene Eesti Põlevkivitööstus and Eestimaa Õlikonsortsium signed similar contracts later.[56] In 1938, 45% of Estonian shale oil was exported exceeding import value of other fuels. It accounted for 8% of Estonia's total export.[57] Although the price of oil shale-based gasoline was at least triple that of global gasoline prices, high production and bilateral agreements supported its export.[55]

The oil shale-fired electrical power industry started in 1924 when the Tallinn Power Station switched to oil shale.[22] In 1933, it reached a capacity of 22 megawatts (MW). Other oil shale-fired power stations were built in Püssi (3.7 MW), Kohtla (3.7 MW), Kunda (2.3 MW), and Kiviõli (0.8 MW). At the beginning of World War II, the total capacity of oil shale-fired power stations was 32.5 MW.[5]

On 9 May 1922 the first international discussion of Estonian kukersite took place at the 64th meeting of the Institution of Petroleum Technologists.[40] Systematic research into oil shale and its products began at Tartu University's Oil Shale Research Laboratory in 1925, initiated by professor Paul Kogerman.[34][58] In 1937, the Ministry of Economic Affairs established the Geological Committee and the Institute of Natural Resources was founded. A department of mining was established at Tallinn Technical University in 1938.[40] Estonian oil shale industries conducted tests of oil shales from Australia, Bulgaria, Germany and South Africa.[59]

German occupation[edit]

Soon after the Soviet occupation in 1940, the entire oil shale industry was nationalised and subordinated to the Mining Office and later to the General Directorate of Mining and Fuel Industry of the Peoples' Commissariat for Light Industry.[60] Germany invaded the Soviet Union in 1941 and the industry's infrastructure was largely destroyed by retreating Soviet forces.[50] During the subsequent German occupation, the industry was merged into a company named Baltische Öl GmbH. This entity was subordinated to Kontinentale Öl, a company that had exclusive rights to oil production in German-occupied territories.[50][60] Baltische Öl consisted of five units (Kiviõli, Küttejõu, Kohtla-Järve, Sillamäe, and Kohtla). Each unit included an oil shale mine and shale oil extraction plant, except Küttejõu, which did not have an associated shale oil extraction plant. The shale oil extraction industry was partially restored and in 1943 it processed 201,600 tonnes of oil shale. Prisoners of war made up about two-thirds of the work force.[50]

The primary purpose of these industries was production of oil for the German Army. In 1942, 592,102 cubic metres (20,909,900 cu ft) of shale oil were transported to Germany.[60] Baltische Öl started construction of new mines and shale oil extraction plants; however, none of them became operational.[50]

While Soviet troops were advancing into Estonia during 1944, about 200 Estonian oil shale specialists were evacuated to Schömberg, Germany, to work at an oil shale industry there, codenamed Operation Desert (Unternehmen Wüste).[58][60] Shale oil extraction plants in Estonia were destroyed and mines were ignited or inundated by the retreating Germans.[50][61] Existing oil shale-fired power stations in Püssi and Kohtla-Järve were also destroyed.[61]

Restoration of the industry after World War II[edit]

A colour photograph of the shale oil facility in Kohtla-Järve. The lower third of the photo is occupied by a curving driveway and the cars parked along it.
Old shale oil extraction plant in Kohtla-Järve (2009)
A black-and-white photograph of an underground oil shale mine, dated to 1970. The worker on the far right is steering a machine to the left of the photo.
Oil shale mining in a sub-surface mine in Estonia (1970)

In 1945–1946 the mining industry was merged into Eesti Põlevkivi (Russian: Эстонсланец, English: Estonian Oil Shale, now Eesti Energia Kaevandused) under the General Directorate of Oil Shale Industry of the USSR (Glavslanets).[62] Shale oil extraction, except the Kiviõli and Kohtla-Nõmme plants, was merged into the Kohtla-Järve shale oil combinate (Russian: Сланцехим, now Viru Keemia Grupp) under the General Directorate of Synthetic Liquid Fuel and Gas of the USSR (Glavgaztopprom). Both organisations were directed from Moscow.[63] New mines were opened near Ahtme (1948), Jõhvi (Mine No. 2, 1949), Sompa (1949), Tammiku (1951) and in the area between Käva and Sompa (Mine No. 4, 1953).[17] The Küttejõu open-pit mine was closed in 1947 and the Küttejõu underground mine was merged with the Kiviõli mine in 1951.[64]

The shale oil industry at Kohtla-Järve and Kiviõli was redeveloped. In 1945, the first tunnel kiln was restored and by the end of the 1940s four tunnel kilns located in Kiviõli and Kohtla-Nõmme had been restored. German prisoners of war contributed most of the labour.[65] Between 1946 and 1951, 13 Kiviter-type retorts were built in Kohtla-Järve. An additional three retorts were constructed between 1981 and 1987. In addition, between 1956 and 1968 two tunnel kilns were in operation at Kohtla-Järve. Eight Kiviter-type retorts were in use at Kiviõli between 1953 and 1963.[5]

In 1947, a pilot Galoter retort unit was built in Tallinn, capable of processing 2.5 tonnes of oil shale per day.[66][67] The first Galoter-type commercial scale pilot retorts were built at Kiviõli in 1953 and 1963 with respective capacities of 200 and 500 tonnes of oil shale per day. The first of these retorts closed in 1963 and the second in 1981.[5][66][68][69] During the 1950s, unsuccessful tests of oil shale underground gasification were conducted at Kiviõli.[3][70][71]

In 1948 an oil shale gas plant in Kohtla-Järve began production and for several decades the gas was used as a substitute for natural gas in Saint Petersburg (then known as Leningrad) and in northern Estonian cities.[57][72][73][74] It was the first time in history when synthetic gas from oil shale was used in households.[72] To enable its delivery, a 200-kilometre (120 mi) pipeline from Kohtla-Järve to Saint Peterburg was built, followed by a 150-kilometre (93 mi) pipeline from Kohtla-Järve to Tallinn.[72] In 1962 and 1963, converting oil shale gas into ammonium was tested; however, for industrial production oil shale gas was replaced with natural gas.[75] Oil shale gas production peaked in 1976 at 597.4 million cubic metres (21.10×10^9 cu ft).[76] Although this gas had become uneconomical by 1958, 276 gas generators operated until 1987.[5][77]

Between 1946 and 1952, uranium compounds were extracted from graptolitic argillite at the Sillamäe Processing Plant (now: Silmet).[78][79][80] More than 60 tonnes of uranium compounds (corresponding to 22.5 tonnes of elemental uranium) were produced from 271,575 tonnes of shale which was mined at the 15-metre (49 ft) deep underground mine.[7][10]

In 1949, the 48 MW Kohtla-Järve Power Station – the first power station in the world to use pulverised oil shale at an industrial scale – was commissioned, followed by the 72.5 MW Ahtme Power Station in 1951.[5]

An oil shale research institute (now a department within Tallinn University of Technology) was founded at Kohtla-Järve in 1958.[81] Preliminary research into oil shale-based chemical production began the same year. These investigations explored the potential for its use in bitumen, synthetic construction materials, detergents, synthetic leathers, synthetic fibres, plastics, paints, soaps, glues, and pesticides.[82] Between 1959 and 1985, 5.275 billion cubic metres (186.3×10^9 cu ft) of mineral wool were produced from oil shale coke, a solid residue of oil shale.[83]

Peak of production[edit]

A colour photograph of the Balti Power Station, highlighting its towers against a partly cloudy sky
The Balti Power Station (2007)
A black-and-white photograph of open-pit mining, dated to 1970, showing the silhouettes of bare hills and extraction machinery
Oil shale open pit mining in Estonia (1970)

In 1965, 510 million cubic metres (18×10^9 cu ft) of oil shale gas were produced and 16.5 million tonnes of oil shale were mined.[84] To ensure sufficient energy supply in Estonia, Latvia and north-west Russia, the world's two largest oil shale-fired power stations (the Narva Power Stations) were built during the 1960s and 1970s.[26][85] Both power stations burned pulverised oil shale. The Balti Power Station was built between 1959 and 1971 and the Eesti Power Station was built between 1969 and 1973.[26] The oil shale demand was increased and consequently new mines were constructed: the underground mines Viru (1965) and Estonia (1972) along with the open-pit mines Sirgala (1963), Narva (1970) and Oktoobri (1974; later named Aidu).[17] The Estonia Mine became the largest oil shale mine in the world.[86] Correspondingly, exhausted smaller mines No.2, No.4, Kukruse, and Käva were closed between 1967 and 1975.[17][87]

Because of the success of oil shale-based power generation, Estonian oil shale mining peaked in 1980 at 31.35 million tonnes and power generation peaked at the same year at 18.9 TWh.[4][26][88] The industry declined during the two decades that followed this peak. Demand for electric power generated from oil shale was reduced by construction of nuclear power stations in the Russian SFSR, particularly by the Leningrad Nuclear Power Station.[4] Notwithstanding this, in 1988 Moscow-based authorities planned a third oil shale-fired power station in Narva with a capacity of 2,500 MW, together with a new mine at Kuremäe. The concept met local opposition and was never implemented.[89]

The Narva Oil Plant, annexed to the Eesti Power Station and operating two Galoter-type 3,000-tonnes-per day retorts, was commissioned in 1980 and has since been updated.[5][69][90] These retorts were designed by Atomenergoproekt and developed in cooperation with the Krzhizhanovsky Institute.[67][69] Started as a pilot plant, the process of converting it to a commercial-scale plant took about 20 years. Eesti Energia, an owner of the shale oil extraction plant, has modernised more than 70% of the equipment that was part of its original design.[68]

The intense pace of exploitation at the time was accompanied by growth in research. In 1968, a branch of the Skochinsky Institute of Mining was established in Kohtla-Järve,[40] and in 1984 the scientific-technical journal Oil Shale was founded in Estonia.[34]

At the end of 1988, the largest underground fire in Estonia which continued 81 days and caused a serious pollution of ground and surface waters, happened in the Estonia mine.[91]

Developments after regaining independence[edit]

A colour photograph of a train with open cars carrying oil shale near Ahtme, dated to June 2007. The locomotive is on the left.
Oil shale cargo train near Ahtme (2007)

In the 1990s, after Estonia regained independence, the oil shale mining continued to decrease due to the restructuring of economy which decreased consumption of electricity.[11][57] Electricity export to Russia stopped. Also shale oil production decreased as the previous markets disappeared.[11] Due to the economic reasons the Tammiku and Sompa mines were closed in 1999, and those at Kohtla and Ahtme were closed in 2001.[87]

In 1995, state owned shale oil producers in Kohtla-Järve and Kiviõli were merged into the single company named RAS Kiviter.[92] In 1997, Kiviter was privatized and a year later it declared insolvency. Its factories in Kohtla-Järve and Kiviõli were sold separately and new oil producers – Viru Keemia Grupp and Kiviõli Keemiatööstus – emerged.[11]

In 1995, the Government of Estonia started negotiations with American company NRG Energy to create a joint venture on the basis of the Narva Power Stations, the largest consumer of oil shale in Estonia. As a part of the deal, 51% of the government owned shares in the oil shale mining company Eesti Põlevkivi was transferred to the Narva Power Stations.[93] The proposed deal with NRG Energy got a strong public and political opposition and was cancelled after NRG Energy failed the deadline to secure financing for this.[94][95] Consequently, the Government transferred its remained shares in Eesti Põlevkivi to a state-owned company Eesti Energia, a parent company of the Narva Power Stations, and Eesti Põlevkivi became a fully owned subsidiary of Eesti Energia.[96]

Oil shale production started to increase again in the beginning of the 21st century. In 2000, the open-pit mines at Viivikonna, Sirgala and Narva were merged into the single Narva open-pit mine.[97] Beginning in 2003, several new mines were opened: the Põhja-Kiviõli open-pit mine in 2003, the Ubja open-pit mine in 2005, and the Ojamaa underground mine in 2013.[3][98][99] By 2006, 90 years after major mining had begun in Estonia, the total amount of mined oil shale achieved one billion tonnes.[8][100] The exhausted Aidu open-pit mine was closed in 2012, followed a year later by the Viru underground mine.[101][102]

In 2004, two power units with circulating fluidised bed combustion boilers were put into operation at the Narva Power Stations.[103] Construction of the new 300 MW Auvere Power Station, located next to the existing Eesti Power Station, began in 2012.[104] In the end of 2012, the Ahtme Power Station was closed.

In 2008, Eesti Energia established a joint venture, Enefit Outotec Technology, with the Finnish technology company Outotec. The venture sought to develop and commercialise a modified Galoter process–the Enefit process–that would enhance the existing technology by using circulating fluidised beds.[105] In 2013, Enefit Outotec Technology opened an Enefit testing plant in Frankfurt.[106][107]

VKG Oil opened a new Galoter-type retort called Petroter in December 2009.[108][109] Two firms participated in its engineering – the retort work was performed by Atomenergoproekt and the condensation and distillation plant work was done by Rintekno of Finland.[110] The company started construction of a second Petroter plant in 2012 and plans to build a third plant.[111][112] Eesti Energia opened a new generation Galoter-type plant using Enefit 280 technology in 2012.[113]

Economic impact[edit]

A colour photograph of the Põhja-Kiviõli oil shale mine near Kohtla-Järve, dated to 2007. Machinery and supporting devices are visible in the lower half and a stream of water traverses the centre of the photo. A cliff on the left is topped with trees; the low hills on the right are bare.
Põhja-Kiviõli oil shale mine near Kohtla-Järve (2007)

The National Development Plan for the Utilisation of Oil Shale 2008–2015 describes oil shale as a strategic energy resource.[114] Other mineral resources in Estonia that are currently mined are peat, dolostone, clays, limestone, sand, and gravel; mineral resources that are potentially mineable are granite, iron ore, and phosphorite.[115][116]

Estonia is the only country in the world that uses oil shale as its primary energy source.[117] In 2012, it supplied 70% of Estonia's total primary energy[118] and accounted for 4% of Estonia's gross domestic product.[29] About 6,500 people (1.1% of the workforce in Estonia) were directly employed in the oil shale industry.[119] In 2011, about one-third of Estonian public research, development and demonstration expenditures (€3.1 million) went to the oil shale sector.[120] A new development plan for 2016–2030 is at a preparatory stage.[29]


Amount of mined oil shale in Estonia (millions of metric tonnes from 1916 to 2013. Source: John R. Dyni,[42] Statistical Office of Estonia)
Dragline excavator in the Narva open-pit mine (2005)

Estonia has adopted a national development plan that limits the annual mining of oil shale to 20 million tonnes.[114] In 2012, 15.86 million tonnes of oil shale were mined.[120] As of 2014, five oil shale mines are in operation. Three of these are open-pit mines and two are underground mines. Plans for opening several new mines are in the preparatory phase. Historically, the ratio of underground mining to open-pit mining has been approximately even, but as usable deposits close to the surface become scarcer, underground mining will probably increase.[121]

The Estonia underground mine at Väike-Pungerja, operated by state owned Eesti Energia Kaevandused, is the largest oil shale mine in the world.[86][122] The other underground mine, operated by privately owned Viru Keemia Grupp, is located at Ojamaa.[98] Both mines use the room and pillar mining method.[3][98] Oil shale mined at Ojamaa is transported to the processing plant by a unique 13-kilometre (8.1 mi) conveyor belt. Although there are similar conveyors in operation in other countries, the one at Ojamaa is an unusually challenging installation since its path contains many curves and sharp turns.[123]

The Narva open-pit mine is operated by Eesti Energia Kaevandused, and the Põhja-Kiviõli open-pit mine is operated by privately owned Kiviõli Keemiatööstus. Both mines use highly selective extraction in three layers of seams.[3] The Narva mine uses a technology that involves breaking up both the overburden and the targeted deposits by blasting and then stripping the rock with relatively large-bucket (10–35 cubic metres or 350–1,240 cubic feet) excavators. The third open-pit mine, operated by Kunda Nordic Tsement which belongs to German HeidelbergCement group, is located at Ubja.[3]

About a quarter of mined oil shale is used for shale oil production and about three quarters for electricity production.[27]

Oil shale mines in Estonia[124]
Mine Type Opened Closed Owner(s)
Pavandu open-pit 1917 1927 Riigi Põlevkivitööstus
Vanamõisa open-pit 1919/1920 1931 Riigi Põlevkivitööstus/Estonian Oil Development Syndicate Ltd./Vanamõisa Oilfields Ltd.
Kukruse open-pit 1920 1920 Riigi Põlevkivitööstus
Küttejõu open-pit 1920 1931 Eesti Küttejõud
Kukruse underground 1921 1967 Riigi Põlevkivitööstus/Esimene Eesti Põlevkivitööstus/Baltische Öl/Eesti Põlevkivi
Kiviõli open-pit 1922 1931 Eesti Kiviõli/Baltische Öl
Ubja underground 1924 1959 Port Kunda/Punane Kunda
Käva underground 1924 1972 Riigi Põlevkivitööstus/Esimene Eesti Põlevkivitööstus/Baltische Öl/Eesti Põlevkivi
Käva open-pit 1925 1930 Riigi Põlevkivitööstus/Esimene Eesti Põlevkivitööstus/Baltische Öl
Ubja open-pit 1926 1955 Port Kunda/Punane Kunda
Pavandu underground 1925 1927 Riigi Põlevkivitööstus
Kiviõli underground 1929 1987 Eesti Kiviõli/Baltische Öl/Eesti Põlevkivi
Viivikonna open-pit 1936 20001 Eestimaa Õlikonsortsium/Baltische Öl/Eesti Põlevkivi
Kohtla open-pit 1937 1937 New Consolidated Gold Fields Ltd.
Viivikonna underground 1940 1954 Eestimaa Õlikonsortsium/Baltische Öl/Eesti Põlevkivi
Kohtla underground 1940 1999 New Consolidated Gold Fields Ltd./Baltische Öl/Eesti Põlevkivi
Ahtme underground 1948 2001 Eesti Põlevkivi
Sompa underground 1948 1999 Eesti Põlevkivi
Sillamäe underground 1949 1952 Kombinat No 7
Mine No. 2 underground 1949 1973 Eesti Põlevkivi
Tammiku underground 1951 1999 Eesti Põlevkivi
Mine No. 4 underground 1953 1975 Eesti Põlevkivi
Sirgala open-pit 1962 20001 Eesti Põlevkivi/Eesti Energia Kaevandused
Viru underground 1965 2012 Eesti Põlevkivi/Eesti Energia Kaevandused
Narva open-pit 1970 ...2 Eesti Põlevkivi/Eesti Energia Kaevandused
Estonia underground 1972/1973 ...2 Eesti Põlevkivi/Eesti Energia Kaevandused
Aidu open-pit 1974 2012 Eesti Põlevkivi/Eesti Energia Kaevandused
Põhja-Kiviõli open-pit 2004 ...2 Kiviõli Keemiatööstus
Ubja (new mine) open-pit 2005 ...2 Kunda Nordic Tsement
Ojamaa underground 2010 ...2 Viru Keemia Grupp
1 Merged into the Narva open-pit
2 Not closed, still operating

Electricity and heat generation[edit]

Eesti Power Station (2004)

National policy, as codified in a 2009 document, prioritises oil shale as a resource for ensuring Estonia's electricity supply.[125] Although the national development plan for the Estonian electricity sector covering the years to 2018 characterizes as threats both the significant environmental impact of oil shale-fired power stations and the very high share of oil shale in electricity production,[126] the plan supports the industry as part of a national energy security strategy.[127]

In 2012, over 85% of oil shale mined in Estonia was used for power generation and about 85% of Estonia's electricity was generated from oil shale.[120][128] Eesti Energia owns the largest oil shale-fuelled power stations (Narva Power Stations) in the world.[1][2] In addition, a new 300 MW station, which will use circulating fluidised bed boiler technology, is under construction in Auvere.[129]

In 2010, 11.4% of the heat supply in Estonia was generated by direct combustion of oil shale and 5.88% by combustion of shale oil. Shale oil was used as a fuel by 9.36% of all boiler houses in Estonia.[130] Heat produced by co-generation at the Balti Power Station is used for district heating of Narva, the third largest city in Estonia with 58,700 inhabitants (2013).[131] The co-generation plants in Kohtla-Järve, Sillamäe, and Kiviõli burn oil shale to produce electrical power and supply district heating to nearby towns.[114] In addition to raw oil shale, the Kohtla-Järve Power Station uses oil shale gas, a by-product of shale oil production, for the same purposes.[130]

Shale oil extraction[edit]

See also: Narva Oil Plant

In 2008, Estonia was the second largest shale oil producer in the world after China.[132] Production was 536,903 tonnes of shale oil in 2010.[130] Most of produced shale oil is exported to European countries as bunker fuel and refinery feedstocks; the remainder is used mainly for a district heating.[117][133]

There are three shale-oil producers in Estonia: VKG Oil (a subsidiary of Viru Keemia Grupp), Eesti Energia Õlitööstus (a subsidiary of Eesti Energia), and Kiviõli Keemiatööstus (a subsidiary of Alexela Energia).[27][130][134] Two processes – the Kiviter process and the Galoter process – are in use for shale oil extraction.[3][71]

Cement production[edit]

Spent shale, a solid residue of oil shale, is used for portland cement production at the Kunda Nordic Tsement factory. In 2002, 10,013 tonnes of spent shale were used for cement production.[83] VKG Plokk, a subsidiary of Viru Keemia Grupp, produces building blocks by using oil shale ash and spent shale, and plans to construct a cement factory.[135][136] The mined waste rock is used for road construction.[3][101]

Environmental impact[edit]

A colour photograph of the un-rehabilitated Aidu open-pit mine. The lower two-thirds of the photo shows hilly land that is mostly brownish-grey. Some small, green trees are growing within this section.
Unrehabilitated land at the Aidu open-pit mine (2007)
A colour photograph of an old semi-coke heap in Kiviõli, dated to 2005, with a large tree in the foreground. The heap is green.
An old semi-coke heap in Kiviõli (2005)

Wastes and land usage[edit]

Annually, the oil shale industry produces 70% of Estonia's ordinary waste and 82% of hazardous waste.[29] Loss of material during mining amounts to about four million tonnes per year; combined with losses incurred during the enrichment process, more than 30% of the resource is lost.[29][137] Former and current oil shale mines occupy about 1% of Estonia's territory.[18] About 500 square kilometres (190 sq mi) or 15% of Ida-Viru County's territory is out of use due to open-pit mines and waste landfills; an additional 150 square kilometres (58 sq mi) has sunk or become unstable due to underground mining.[138]

The mining and processing of about one billion tonnes of oil shale in Estonia has created about 360-370 million tonnes of solid waste. Combustion ashes are the largest component (200 million tonnes), followed by mining waste (90 million tonnes) and spent shale (mainly semi-coke, 70–80 million tonnes).[83][139] According to the European Union waste list, oil shale ash and spent shale are classified as hazardous waste.[140] As of 2006, semi-coke heaps near Kohtla-Järve and Kiviõli covered 180–200 hectares (440–490 acres) and ash heaps near Narva covered 210 hectares (520 acres).[139] These heaps protruding from the flat landscape are regarded as landmarks and as monuments to the area's industrial heritage.[141]

Approximately 73 million tonnes of graptolitic argillite as overlying deposit were mined and piled in waste heaps in the process of phosphorite–ore mining near Maardu in 1964–1991.[7] The oil shale waste heaps pose a spontaneous ignition risk due to their remaining organic content.[137] The waste material, particularly semi-coke, contains pollutants including sulphates, heavy metals, and polycyclic aromatic hydrocarbons (PAHs), some of which are toxic and carcinogenic.[142][143]

Water usage and pollution[edit]

For each cubic meter of oil shale mined in Estonia, 25 cubic metres (880 cu ft) of water must be pumped from the mine area.[1] This alters the groundwater circulation and its quality, lowering groundwater levels and releasing mine water into surface water bodies, such as rivers and lakes.[137] As a result of mining activities, groundwater moves towards the excavation cavities. A 220 square kilometres (85 sq mi) underground water body that holds over 170 million cubic metres (140,000 acre·ft) has formed in eight abandoned underground mines – Ahtme, Kohtla, Kukruse, Käva, Sompa, Tammiku, No.2 and No.4.[87][144][145] Mining activities have contributed to lower water levels in 24 lakes out of 39 in the Kurtna Lake District.[137]

The process of pumping water out from the mining area introduces oxygen via aeration and thereby oxidises the rock's pyrite. Pyrite contains sulfur, and one consequence of its oxidation is an influx of significant amounts of sulphates into mining water.[137][144] In some lakes, sulphate levels have increased tens of times compared to the pre-mining period. Suspended mineral matter in the mine water pumped into these lakes has changed the composition of the lakes' sediments. However, it has been found that this disturbance diminishes over time; studies show that sulphates and iron in mining water decrease to levels that meet drinking water quality standards about five years after mine closure.[144]

The process and waste waters used in shale oil extraction contain phenols, tar, and several other environmentally toxic products.[139][142] Power stations use water for hydraulic transportation of oil shale ash to the ash heaps. Created oil shale ash is mixed with water at a ratio of 1:20 and the resulted mixture, known as "ash pulp", is pumped to the heaps.[146] Consequently, the transportation water then becomes highly alkaline. The total volume of formed alkaline water is 19 million cubic metres (670×10^6 cu ft).[147] Another source of water pollution is aqueous leachates from oil shale ash and spent shale. About 800,000 to 1,200,000 cubic metres (28,000,000 to 42,000,000 cu ft) of toxic leachate from the Narva ash heaps inflows annually to the Narva River and further to Gulf of Finland.[143] Before the closure of old semi-coke heaps in Kohtla-Järve and Kiviõli, additionally about 500,000 cubic metres (18,000,000 cu ft) of leachates reached through the Kohtla and Purtse rivers to the Baltic Sea annually.[139] The toxicity of leachate is mainly caused by the alkalinity and sulphides; leachate also includes chlorides, oil products, heavy metals, and PAHs.[139][143]

Air emissions[edit]

Oil shale-fired power stations pollute air with the fly ash and flue gases like carbon dioxide, nitrogen oxides, sulfur dioxide, and hydrogen chloride. In addition to Estonia, this pollution is received also by Finland and Russia.[148] Annually, the industry emits into the atmosphere about 200,000 tonnes of fly-ash, including heavy metals, carbonates, alkaline oxides (mainly calcium oxide), and harmful organic substances (PAHs). About 30% of the fly-ash is calcium oxide; a portion of calcium oxide is neutralised by atmospheric carbon dioxide.[137] According to the study of 2001, concentration of particulate matter in fly-ash is 39.7 mg per one cubic metre.[149] The most hazardous are particles with a diameter less than 2.5 micrometres (9.8×10−5 in); these particles are associated with an increase in cardiovascular mortality and a number of premature deaths in Estonia.[150]

Combustion of oil shale releases more carbon dioxide than any other primary fuel. It is the chief source of greenhouse gas emissions in Estonia, accounting for more than 70% of all such emissions.[29][120] Deposition of oil shale ash and semi-coke causes air pollution by the dust of these substances.[139]


Various efforts have reduced the industry's environmental impact. Fluidised bed combustion generates fewer PAHs than the earlier, dominant technologies that burned pulverised oil shale.[147] Reclamation and reforestation of exhausted mining areas has been carried out since the 1970s.[151] In 2010–2013, a €38 million project was implemented for the environmentally safe closing of 86 hectares (210 acres) of semi-coke and ash heaps.[138] In accordance with a European Union waste framework directive, the heaps were covered with waterproof material, new topsoil, and sod.[152] In Kiviõli, a 90-metre (300 ft) semi-coke heap, the highest artificial hill in the Baltic countries, was converted into a ski centre.[153] The former Aidu open-pit mine was converted into a rowing course.[154]


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  • Saarnak, Martin; Uibopuu, Lembit; Valgma, Ingo; Nurme, Martin; Väizene, Vivika (2014). "6. Eesti põlevkivi kaevandamisviisid" [6. Mining methods of Estonian oil shale]. In Valgma, Ingo. Mäendus [Mining] (PDF) (in Estonian). Institute of Mining. Tallinn University of Technology. pp. 55–68. ISBN 978-9949-430-80-2. 

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