Oil shale in Estonia

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Outcrop of Ordovician kukersite oil shale, northern Estonia

Oil shale in Estonia is an important resource for the national economy. Estonia's oil shale deposits account for just 17% of total deposits in the European Union but the country generates 90% of its power from this source. The oil shale industry in Estonia employs 7,500 people—about one percent of the national work force—and accounts for four percent of its gross domestic product.[1]

There are two kinds of oil shale in Estonia – graptolitic argillite (claystone) and kukersite.[2] The first attempt to establish an open-pit oil shale mine and to start oil production was undertaken in 1838.[3] Modern utilization of oil shale commenced in 1916. Production began in 1921 and the generation of power from oil shale in 1924.[4]

In 2005 Estonia was the leading producer of shale oil in the world. Of all the power plants fired by oil shale, the largest was in this country.[1][5] As of 2007, six mines (open-pit or underground) were extracting oil shale in Estonia.[2]


There are two oil shale types in Estonia–graptolitic argillite (claystone) and kukersite.[2]

Graptolitic argillite[edit]

Pyrite (FeS2) inside graptolite argillite of the Türisalu Formation of (found in the Türisalu cliff)
Isopach map of the Ordovician graptolitic argillite in northern Estonia. Thickness in meters.

The marine-type Estonian graptolitic argillite (also known as Dictyonema argillite, Dictyonema oil shale, Dictyonema shale or alum shale) of an Early Ordovician age is a brown lithified claystone of the Türisalu formation belonging to the group of black shales of sapropelic origin.[6][7] It occurs at the foot of the North-Estonia Klint from the Pakri Peninsula to Narva on an area of about 11,000 square kilometres (4,200 sq mi).[8][9] Together with western Estonian islands, it occurs in the area about 12,200 square kilometres (4,700 sq mi).[7] The thickness of the graptolitic argillite layer varies from less than 0.5 metres (1 ft 8 in) to 8 metres (26 ft) in the Western part of Estonia, and lies at a depth of 10 to 90 metres (33 to 295 ft).[8][10] It formed some 480 million years ago.[9]

Geological reserves of graptolitic argillite in Estonia were estimated approximately 60–70 billion tonnes.[6][9] Although reserves of the graptolitic argillite surpass those of kukersite, its quality is poor as a source for the energy production. The heating value of the graptolitic argillite is 5–8 MJ/kg, and the Fischer Assay oil yield is 3–5%.[8] The organic content of the graptolitic argillite of north-western Estonia varies from 10 to 20%, and it contains up to 9% pyrite (mainly 2.4–6%). It also contains a small scale of heavy metals, such as uranium (up to 1,200 ppm or 300 g/t), molybdenum (up to 1,000 ppm or 600 g/t), vanadium (up to 1,600 ppm or 1200 g/t), and nickel.[2][7] The mineral content of the graptolitic argillite includes K-feldspars, quartz, clay minerals, light-brown phosphatic ooids, and accessory amounts of zircon, tourmaline, garnet, rutile, chalcopyrite and glauconite, in western Estonia also corundum, amphiboles and disthene. The quartz content in graptolitic argillit is higher in east Estonia and the clay minerals content is higher in western Estonia.[7] The graptolitic argillite of north-western Estonia has sulfur content of 2–4%; it contains fewer metals and up to 17% of organic matter.[2] In the north-east Estonia the organic matter of graptolitic argillite has an atomic ratio of carbon to hydrogen about 9.[7]

Although the name Dictyonema argillite is widely used instead of graptolitic argillite, this name is misnomer as fossils in the rock are not graptolites from the genus Dictyonema but from the genus Rhabdinopora.[9]


Location of the kukersite deposits within the Baltic Oil Shale Basin in northern Estonia and Russia

Kukersite is a light-brown marine-type oil shale of the lowest Upper Ordovician formation, formed some 460 million years ago.[9] It was named after the German name of the Kukruse Manor in the north-east of Estonia.[2][9][11][12]

Estonian kukersite deposits are one of the world's highest-grade deposits with organic content varying from 15% to 55% with average more than 40%, and it has 65–67% conversion ratio into shale oil and oil shale gas.[9][13] Fischer Assay oil yield is 30 to 47%.[14] Its organic matter has an atomic ratio of hydrogen to carbon is 1.51 and the mean calorific value of kukersite is 3600 kcal/kg.[9]

The principal organic component of kukersite is telalginite, derived from the fossil green alga, Gloeocapsomorpha prisca, which has affinities with the modern cyanobacterium, Entophysalis major, an extant species that forms algal mats in inter-tidal to very shallow subtidal waters.[14] Matrix minerals dominantly include low-magnesium calcite, dolomite, and siliciclastic minerals. They are not rich in heavy metals.[10]

Fossils in Ordovician period kukersite oil shale, northern Estonia

Kukersite was deposited in a shallow marine basin. It lays in the depth of 7 to 170 metres (23 to 558 ft).[8][13] Kukersite occurs within the Kukruse and Uhaku stages of the Viivikonna and Kõrgekallas formations, as an often calcareous layer.[9][14][13] The main 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) and together with the Leningrad deposit, which is an extension of the Estonian deposit, form the Baltic Oil Shale Basin.[9][8][15][16] The Estonian deposit, which covers about 2,000 square kilometres (770 sq mi), is used industrially; the Tapa deposit is not accounted as reserves due its lower value which makes its extraction economically inexpedient.[16][17] In northern Estonia there are a total of 50 oil shale layers of kukersite, of which six lowest form a 2.5-to-3-metre (8 ft 2 in to 9 ft 10 in) thick mineable bed.[2] In this part kukersite lies near the surface while southward and westward its depth increases and its thickness and quality decreases.[16]

Estonia's kukersite represents about 1.1% of global and 17% of European oil shale resources.[18] The total kukersite oil shale resources in Estonia are estimated to be about 4.8 billion tonnes, including 1.3 billion tonnes of active resources.[19] Active resource is defined as resource in the areas without environmental restrictions with an energy rating at least 35 GJ/m2 and the calorific value at least 8 MJ/kg.[16] Recoverable reserves—resource that is possible to extract–comprise up to 50% of active resources.[19]


Early history[edit]

The first written information about oil shale in Estonia were made by August Wilhelm Hupel in 1777.[17] According to Peter Simon Pallas, the occurrence of burning rock on the southern coast of the Gulf of Finland occurs in the travel notes of the 18th century naturalist and explorer Johann Anton Güldenstädt.[4][17] According to Paul Kogerman, Estonia's former Minister of Education and the founder of the oil shale chemistry, Estonian oil shale was discovered by a professor of University of Tartu Otto Moritz Ludwig von Engelhardt.[12]

The first scientific research on the oil yield of Estonian oil shale was carried out at the St. Petersburg Imperial Academy of Sciences in 1791 by a German chemist Johann Gottlieb Georgi. The paper was based on the samples collected on the territory of Kohala Manor near Rakvere.[17] In 1838—1839, a Baltic German geologist Gregor von Helmersen described in detail the Vanamõisa oil shale deposit. In 1838, he undertook the first attempt to establish an open-pit in the vicinity of Rakvere and attempted to obtain oil from the Vanamõisa oil shale deposit by distillation.[3][20] Although the attempt of shale oil distillation failed, oil shale was used as a low-grade fuel.[21] In the nineteenth century, the geology and chemistry of oil shale were also studied in the University of Tartu by Georg Paul Alexander Petzholdt, Alexander Gustav von Schrenk, Carl Ernst Heinrich Schmidt, Carl Friedrich Schmidt, and others.[4][17]

Beginning of oil shale industry[edit]

Historical monument at the location where the first tonnes of oil shale were mined

Studies of Estonian oil shale resources and mining possibilities intensified in the beginning of 20th century because of industrial development of Saint Petersburg and a shortage of fuel resources in the region. In 1910, there was a plan of construction of a large-scale shale oil plant in Estonia. The coming of World War I, coupled with a serious fuel crisis, accelerated these studies.[4] In 1916, a group of geologists led by Nikolay Pogrebov were sent to Estonia to organize the mining of oil shale and its transportation to St. Petersburg. In June 1916, the first tonnes of oil shale were mined at Pavandu and were delivered to the Petrograd Polytechnical Institute for large-scale experiments.[22] This is considered as a beginning of the Estonian oil shale industry.[9] Oil shale was utilized in Petrograd at gasworks and was also burned in boiler houses. For large-scale oil shale utilization, construction of oil shale-fired power plants and shale oil thermal processing factories was planned. However, Germany occupied Estonia and the following Estonian War of Independence caused cancellation of these plans.[4] At the same time, experiments on the uses of oil shale started in Estonia. Open-pit mines were opened at Kukruse by Böckel & Co. and at Järve by Mutschnik & Co.[9][23]

In 1917, Russian paleobotanist Mikhail Zalessky named kukersite oil shale after the Kukruse settlement.[11][17] At the same year the state enterprise Kütuse Erinõupidamise volinik põlevkivi kokkuostu ja varumise alal (English: Special Commissioner on oil shale purchase and stockpiling) started preparations for construction of oil shale mine at Pavandu.[23] In February 1918, the oil shale basin in North-East Estonia was occupied by German troops and mining activities were carried out by Internationales Baukonsortium (English: International Construction Consortium). However, before the end of the occupation at the same year, only a trainload of oil shale was mined and sent to Germany for investigation and experimenting with a retort constructed by Julius Pintsch A.G. (Pintsch's generator).[24]

Development during Estonia's independence[edit]

On 24 November 1918, Riigi Põlevkivitööstus (English: Estonian State Oil Shale Industry, later: Esimene Eesti Põlevkivitööstus (English: First Estonian Oil Shale Industry), predecessor of nowadays Viru Keemia Grupp) was established as department of the Ministry for Trade and Industry, and it took over all existing open-pit mines.[24] 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 foreign investors started their oil shale activities in Estonia. Underground mines were opened at Kohtla (1937), and open-pit mines were opened at Kiviõli (1922; since 1930 underground mine) Küttejõu (1925), Ubja (1926) and Viivikonna (1936).[4] Initially, oil shale was used primarily in the cement industry, for firing in locomotive furnaces, and as a household fuel. The first large industrial consumer of oil shale were the Port Kunda cement factory (now Kunda Nordic Cement), 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 Aseri.[4][25] In 1925, Tallinn pulp factory Põhja paberi- ja puupapivabrik acquired a mining company Eesti Küttejõud, which was established in 1922 by the Union of Estonian industrialists as the first private oil shale-mining company. As of 1925, all locomotives in Estonia were powered by oil shale.[24] Systematic research of oil shale and its products began in Estonia in 1925, initiated by professor Paul Kogerman.[20][26]

Shale oil production started in Estonia in 1921, when Riigi Põlevkivitööstus built 14 experimental oil shale processing retorts in Kohtla-Järve.[4][27] These retorts used vertical retort technology of Julius Pintsch, the forerunner of current Kiviter processing technology. Each retort processed 40 tonnes of oil shale per day and produced an oil yield of 18%.[27] Together with the oil plant, an oil shale research laboratory was founded in 1921.[9] In 1924, a British investors-owned Estonian Oil Development Syndicate Ltd. (later Vanamõisa Oilfields Ltd) bought a open-pit mine in Vanamõisa and opened an oil plant which used horizontal retort (fusion retort) technology.[24][27][2] The plant included two retorts with processing capacity of 15 tonnes of oil shale per day each; however, due to to technical problems the plant was eventually abandoned in 1931.[24][27] The German-owned company Eesti Kiviõli (German: Estländische Steinöl, English: Estonian Stone Oil, predecessor of Kiviõli Keemiatööstus), established in 1922 and affiliated with G. Scheel & Co. and Mendelssohn & Co., built four tunnel kilns between 1927 and 1938.[4][24][28] In 1935, it included a contract with the German Kriegsmarine to supply shale oil as a fuel for ships.[28] Swedish owned Estländska Oljeskifferkonsortiet (Estonian: Eestimaa Õlikontsortsium; English: Estonian Oil Consortium), controlled by Marcus Wallenberg, was founded in 1926 to build an oil plant in Sillamäe.[24][29] The consortium built a tunnel oven in 1928. However, due to recession production halted in 1930 and was restarted only in 1936.[27][24] The second tunnel oven was added in 1938.[24] In 1936, it produced 15,000 tonnes of oil, including 2,400 tonnes of gasoline.[27] In 1931, The New Consolidated Gold Fields Ltd. of the United Kingdom built an oil factory at Kohtla-Nõmme equipped with eight rotating retorts (Davidson's retorts).[4][27] Each retort had processing capacity of 15 tonnes of oil shale per day.[27] This facility was closed in 1961.[4] In 1939 Estonia mined 1.453 million tonnes of oil shale and produced 181,000 tonnes of shale oil, including 22,500 tonnes of gasoline. The largest shale oil producer was Eesti Kiviõli by 70,000 tonnes followed by Esimene Eesti Põlevkivitööstus by 61,000 tonnes. The mining and oil industry employed 6,150 persons.[28]

The oil shale-fired power industry started in 1924, when the Tallinn Power Plant switched to oil shale.[15] Afterward oil shale-fired power plants were built in Püssi, Kohtla, Kunda, and Kiviõli. At the beginning of World War II, the total capacity of oil shale power plants was 32.5 MW. These power plants used mainly furnaces with a movable-bar sloping grate (Krull-Lomshakov or Ilmarine-type).[4]

On 9 May 1922 Estonian kukersite issues were discussed first time internationally at the 64th meeting of the Institution of Petroleum Technologists. In 1937, the Geological Committee at the Ministry of Economical Affairs and the Institute of Natural Resources were established. In 1938, the department of mining was established at the Tallinn Technical University.[30]

German occupation[edit]

After beginning of the Soviet occupation in 1940, all oil-shale industry was nationalized and subordinated to the Mining Office and later to the General Directorate of Mining and Fuel Industry of the Peoples' Commissariat for Light Industry.[24] In 1941, the industry was largely destroyed by the retreating Soviet forces.[28] During the German occupation, the industry was merged into a company named Baltische Öl GmbH – Berlin, which was subordinated to Kontinentale Öl, an affiliate of IG Farben.[24][28] It was divided into five units (Kiviõli, Küttejõu, Kohtla-Järve, Sillamäe, Kohtla), each consisting oil shale mine and shale oil plant, except Küttejõu, which did not have its own oil plant. The oil industry was partly restored and in in 1943 its annual capacity accounted 201,600 tonnes of shale. More than half of work forces used that time were war prisoners.[28] The main purpose of the industry was oil production for the German Army. In 1942, 592,102 cubic metres (20,909,900 cu ft) of shale oil was transported to Germany.[24]

When the Soviet troops advance into Estonia in 1944, about 200 Estonian oil shale specialists were evacuated to Schömberg, Germany to work at the oil shale industry planned as a part of the Operation Desert (Unternehmen Wüste).[24][26] Oil plants in Estonia were destroyed and mines were ignited or inundated.[9][28] Also existing oil shale-fired power stations in Püssi and Kohtla-Järve were destroyed.[9]

Restoration of the industry after World War II[edit]

Old shale-oil plant in Kohtla-Järve

After World War II, in 1946 oil-shale mining was merged into Eesti Põlevkivi (Russian: Эстонсланец, now Eesti Energia Kaevandused) under Glavslanets while shale oil extraction with exception of the Kiviõli and Kohtla-Nõmme plants was merged into the Kohtla-Järve shale oil combinate (Russian: Сланцехим, now Viru Keemia Grupp) under Glavgaztopprom—both all-Soviet structures directed from Moscow.[24] New mines were opened in Ahtme (1948), Jõhvi (mine no. 2; 1949), Sompa (1949), Tammiku (1951) and between Käva and Sompa (mine no. 4; 1953).[17] Küttejõu open-pit mine was closed in 1947 and Küttejõu underground mine was merged with Kiviõli mine in 1951.[31]

The shale oil industry was developed at Kohtla-Järve and Kiviõli. In 1945, the first tunnel kiln was restored and by the end of 1940s four tunnel kilns locating in Kiviõli and Kohtla-Nõmme were restored. Most of the labour this time were German war prisoners.[24] Between 1946 and 1951, 13 Kiviter-type retorts were built in Kohtla-Järve with an additional three retorts built between 1981 and 1987. In addition, between 1956 and 1968 two tunnel kilns were in operation at Kohtla-Järve. From 1953 to 1963, eight Kiviter-type retorts were in use at Kiviõli.[4]

In 1947, a pilot unit of the solid heat carrier-type Galoter retort was built in Tallinn with capacity of 2.5 tonnes of oil shale per day.[24][32] The first Galoter-type commercial scale pilot retorts were built at Kiviõli in 1953 and 1963 (closed in 1963 and 1981 respectively) with capacities of 200 and 500 tonnes of oil shale per day respectively.[4][33][24][34]

From 1948, after commissioning of the shale gas plant in Kohtla-Järve, Estonian-produced oil shale gas was used in Leningrad and in northern Estonian cities as a substitute for natural gas.[24][35][36][37] It was the first time in history when synthetic gas from oil shale was used as household gas. For this purpose, a 200-kilometre (120 mi) long pipeline from kohtla-Järve to Leningrad and later 150-kilometre (93 mi) long pipeline from Kohtla-Järve to Tallinn were built. In 1962–1963, converting oil shale gas into ammonium was tested; however, for industrial production oil shale gas was replaced with natural gas.[24] Oil-shale gas production peaked in 1976 by 597.4 million cubic metres (21.10×10^9 cu ft).[38] 276 gas generators were operational until 1987.[4]

During 1946–1952, graptolitic argillite was used for uranium production at Sillamäe Processing Plant.[10][39][40] 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.[9][7]

In 1949, the Kohtla-Järve Power Plant – the first power plant in the world using pulverized oil shale at an industrial scale – was commissioned with capacity of 48 MW, followed by the Ahtme Power Plant in 1951 with capacity of 72.5 MW.[4]

In 1958, an oil shale research institute (now department of Tallinn University of Technology) was founded at Kohtla-Järve.[24]

Peak of production[edit]

BaltiPower Plant

In 1965, 510 million cubic metres (18×10^9 cu ft) of oil shale gas was produced and 16.5 million tonnes of oil shale was mined.[24] In 1960–1970s world two largest oil shale fired power plants (known as the Narva Power Plants) using pulverized oil shale were built near Narva. The Balti Power Plant was built between 1959 and 1971, and the Eesti Power Plant was built between 1969 and 1973.[16] This increased the demand for oil shale and consequently Viru (1965) and Estonia (1973) underground mines, and Sirgala (1963), Narva (1970) and Oktoobri (later named Aidu; 1974) open pit-mines were opened.[17] The Estonia Mine became the largest oil shale mine in the world.[41] At the same time mines no.2, no.4, Kukruse and Käva were closed.[17]

Because of the success of oil shale-based power generation, Estonian oil shale production peaked in 1980 at 31.35 million tonnes and power generation peaked at the same year at 18.9 TWh.[3][16]

The Narva Oil Plant, annexed to the Eesti Power Plant and operating two Galoter-type 3000 tonnes per day retorts, was commissioned in 1980.[4][34][42] These retorts were designed by AtomEnergoProject and developed in cooperation with the Krzhizhanovsky Institute.[32][34] Started as a pilot plant, the process of converting it to commercial scale plant took about 20 years. During this period, Eesti Energia, an owner of the oil plant, has modernized more than 70% of the equipment compared to the initial design.[33]

In 1968, the branch of Skochinsky Institute of Mining was established in Kohtla-Järve.[30] In 1984, the scientific-technical journal Oil Shale was founded in Estonia.[20]

During the 1980–1990s oil shale production in Estonia decreased due to reduced demand from the power generation industry. It was mainly affected by construction of the nuclear power plants in the Soviet Union, particularly Leningrad Nuclear Power Plant.[3]

Developments after regaining independence[edit]

Oil shale cargo train near Ahtme (20 June 2007)

Tammiku and Sompa mines were closed in 1999, and Kohtla and Ahtme mines were closed in 2001.[43] In 2000, Viivikonna, Sirgala and Narva open-pit mines were merged into single Narva open-pit mine.[44] Aidu open-pit mine was closed in 2012 and Viru underground mine in 2013.[45][46] New mines were opened by Kiviõli Keemiatööstus (Põhja-Kiviõli open-pit mine; 2003), Kunda Nordic Tsement (Ubja open-pit mine; 2005) and Viru Keemia Grupp (Ojamaa open-pit mine; 2006).[2] In 2006, 90 years after beginning of mining activities, the total amount of mined oil shale reached to one billion tonne.[9][47]

In 2004, two power units with circulating fluidized bed combustion boilers were put into operation at Narva Power Plants.[4] In 2012, construction of the new 300 MW Auvere Power Plant, located next to the existing Eesti Power Plant, began.[48] At the end of 2012, the Ahtme Power Station was closed.

In 2008, Eesti Energia, established with the Finnish technology company Outotec a joint venture called Enefit Outotec Technology to develop and commercialize a modified Galoter process–the Enefit process–which combines the current process with circulating fluidized bed technologies.[49] In 2013, Enefit Outotec Technology opened an Enefit testing plant in Frankfurt.[50][51]

In December 2009, VKG Oil opened a new Galoter-type retort called Petroter.[52][53] Engineering of the retort was done by Atomenergoproject; engineering of the condensation and distillation plant was done by Rintekno of Finland.[54] The company started construction of the second Petroter plant in 2012 and plans to build also the third plant.[55][56] In 2012 also Eesti Energia opened a new generation Galoter-type plant using Enefit 280 technology.[57]


Oil-shale industry accounts 4% of Estonia's GDP.[19] About 6,500 people, or 1.1% of the workforce in Estonia is directly employed in the oil-shale industry.[58] In 2012, 70% of total primary energy supply in Estonia originated from oil shale.[18]


Dragline excavator in the Narva open-pit mine (26 April 2005)

In 2012, Estonia mined 15.86 million tonnes of oil shale.[18] Estonia has adopted the "National Development Plan for the Use of Oil Shale 2008-2015", which limits the annual mining of oil shale to 20 million tonnes.[59] New development plan for 2016–2030 is at the preparatory stage.[19]

As of 2014, five oil shale mines are in operation. The historical ratio of underground mining to open-pit mining is approximately fifty-fifty, although it is tending to move away from open-pit production as bed depths increase.[3]

The Narva open-pit mine, operated by Eesti Energia Kaevandused, uses surface mining technology of stripping with relatively big bucket (10–35 cubic meters) excavators. Both the overburden and the bed are at first broken up by blasting. Stripping is done with smaller excavators in open-pits with thin overburden using front end loaders and hydraulic excavators. The Narva open-pit mine and the Põhja-Kiviõli open-pit mine, operated by Kiviõli keemiatööstus, use highly selective extraction in three layers of seams.[2] Other open-pit mines are Ojamaa open-pit mine, operated by Viru Keemia Grupp, and Ubja open-pit mine, operated by Kunda Nordic Tsement.[2]

Oil shale mined at Ojamaa mine is transported to the processing plant by the unique 13-kilometre (8.1 mi) belt conveyor. Although there are similar conveyors in operation in other countries, the conveyor at Ojamaa is unique due to a large number of curves and sharp turns.[60]

The only underground mine—Estonia mine—exploits room and pillar method. Longwall mining, used earlier, was abandoned in 1990s.[2] The Estonia Mine, opened in 1972, is the largest oil shale mine in the world.[41] It is operated by Eesti Energia Kaevandused.

Shale oil extraction[edit]

In 2008, Estonia was the second largest shale oil producer in the world after China with 355,000 tonnes of shale oil.[3] There are three shale oil producers in Estonia: VKG Oil (a subsidiary of Viru Keemia Grupp), Narva Oil Plant (a subsidiary of Eesti Energia) and Kiviõli Keemiatööstus (a subsidiary of Alexela Energia).[2]

Electricity generation[edit]

Eesti Power Plant

In 2012, over 85% of mined oil shale in Estonia was used for power generation and about 85% of Estonia's electricity is generated from oil shale.[18][61] Eesti Energia owns the largest oil shale-fuelled power plants (Narva Power Plants) in the world.[5] In addition, a new 300 MW plant, which will use circulating fluidized bed boiler technology, is under construction in Auvere.[62]

Cement production[edit]

The spent shale (semi-coke) is used for portland cement production at the Kunda Nordic Tsement factory. In 2002, 10,013 tonnes of semi-coke were used for cement production.[63] 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.[64][65]

Environmental impact[edit]

Unrehabilitated land in the Aidu open-pit mine

The mining and processing of about one billion tonnes of oil shale in Estonia has created about 360-370 million tonnes of solid waste, of which 90 million tonnes is a mining waste, 70–80 million tonnes is a semi-coke, and 200 million tonnes are combustion ashes.[66] It produces each year 70% of Estonian ordinary waste and 82% of hazardous waste.[19] The losses of oil shale during mining account about four million tonnes per year; together with losses during the enrichment process, more than 30% of the resource is lost.[19][67] Former and current oil-shale mines account about 1% of Estonia's territory.[9] 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; additional 150 square kilometres (58 sq mi) has sunk or become unstable due to underground mines.[68] Approximately 73 million tonnes of graptolitic argillite as overlying deposit was mined and piled in waste heaps in the process of phosphorite–ore mining near Maardu in 1964–1991.[7] Exhausted open-pit areas are gradually being regenerated through land recultivation and reforestation.[3]

Due to remaining organic matter oil-shale waste heaps pose a risk of self-ignition.[67] The waste material, particularly semi-coke, may consist of several pollutants including sulfates, heavy metals, and Polycyclic aromatic hydrocarbons, some of which are toxic and carcinogenic.[69][70] In 2010–2013, a €38 million project was implemented for environmentally-safe closing of 86 hectares (210 acres) of semi-coke and ash heaps.[68] According to the European Union waste framework directive, the heaps were covered with waterproof material, new topsoil, and sod.[71] In Kiviõli,a 90-metre (300 ft) semi-coke heap, the highest artificial hill in the Baltic countries, was converted into a ski-center.[72]

For each cubic meter of oil shale mined in Estonia, 25 cubic meters of water must be pumped from the mine area.[73] This results with an altering the groundwater regime and water quality due to a lowering of the groundwater level and a releasing mine water into surface water bodies. Mining activities have contributed to the water level lowering in 24 lakes out of 39 in the Kurtna Lakes district.[67] Eight abandoned mines—Ahtme, Kohtla, Kukruse, Käva, Sompa, Tammiku, no.2 and no.4—have formed an underground water body.[43]

The process waters and waste waters from the oil shale processing contain phenols, tar and several other products, separable and toxic to the environment.[66]

Oil shale combustion is the main source of carbon dioxide and other gases emissions in Estonia, accounting more than 70% of all emissions.[19] Around 200,000 tonnes of fly-ashh is emitted each year into the atmosphere.[67]


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