OIL SHALE MINING, LEGACY, IMPACT AND LAND USE

Riho

Mõtlep

25. Apr. 2025

OIL SHALE – KUKERSITE

• Name derives from Kukruse village in Ida-Virumaa
• Formed ~450 My ago in shallow warm salt sea
• Layer of algae (Gloeocapsamorpha prisca) mixed with clay and lime minerals

OIL SHALE – OCCURRENCE

• Two OS basins: ESTONIA and TAPA
• Estonia deposit is used
• Reserves: Active ~1.3 Gt

Passive ~3.3 Gt

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• Graptolite argillite

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OIL SHALE – MINING HISTORY

• First written records from Mesopotamia, Creeks and

Romans.

• Oil retorting as such from the 14th Century in Europe.
• 19th c. mainly kerosene, lighting oil, paraffin wax.
• Estonian oil shale mining industry started in 1916. As fuel for cement industry, household fuel, retorted to shale-oil.
• In 1930s Estonia mined roughly 1 Mt of oil shale yearly.
• Mining peaked in 1980 with 31 Mt. Last 20 years 12-15 Mt/y on average.
• Total about 1 Gt of OS has been mined so far

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UNDERGROUND > 30+ m 300+ km2

OPENCAST < 30+ m 130 km2

OIL SHALE – MINING HISTORY and PRESENT

• OS industrial expansion started after WWII.
• For shale oil production, and in 1949 first OS powered power plant was comissioned in Kohtla-Järve. Followed by Balti and Eesti PP in 1965 and 1973, respectively.
• OS is used for power generation and oil production

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• Figures in 2023:
• Taxes: ~160 M eur
• Employees: ~5500
• Investments: ~250 Meur
• Sales: 1.1 Geur

Balti PP

Eesti PP

80%

20%

OIL SHALE – RESOURCE

1 TONNE OF OIL SHALE

Iizmar.ee

Geographical.co.uk

Vectorstock

850 kWh

870 kg CO2

125 kg

35 Nm3

180 kg CO2

450-500 kg

Postimees

500 kg

electricity

CO2 from PP

from oil production

ash

Mining waste

ELECTRICITY

OIL RETORTING

WASTE STREAMS

3000 kg

OIL SHALE – ASH WASTE

• ~50% of OS remains unburnt
• Ash is transported as an ash-water slurry (ratio 1:20) through the pipe system to the ash plateaus

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• Hydrotransport and landfilling initiates ash hydration and changes in ash composition

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OIL SHALE – ASH WASTE

• Ash waste :

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Ash

Hydrated ash

Semicoke

• Calcite / lime
• Residual minerals
• Ca-(Mg)-silicates
• Klinker minerals
• Sulfate phases

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• Calcite / portlandite
• Residual minerals
• Ca-(Mg)-silicates
• Klinker minerals
• Sulfate phases
• C-S-H gel

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• Calcite / dolomite
• Residual minerals
• Ca-(Mg)-silicates
• Klinker minerals (low)
• Sulfate phases
• Emits H2S

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Black shale-oil ash

estonia.ee

estonia.ee

Land subsuidence on ground surface

OIL SHALE INDUSTRY & ENVIRONMENT

• Atmospheric emissions
• Old pulverized combustion boilers (high gas emissions) decomissioned
• New filter systems fitted to catch particulate matter and NOx gases
• High ETS (Emissions Trading System) prices and OS energy is pushed out

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IMF

OIL SHALE INDUSTRY & ENVIRONMENT

Waste generation - Related to chemical composition – high mineral content

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• Mining waste (4-6 Mt/y) – inert limestone with <30% kukersite organics
• Reuse now is roughly 100%
• Ash: Electricity production ash (4-6 Mt/y) - not hazardous - Alkalinity

Oil retorting ash – black ash contains around 1 (3)% organics, but not organic contaminants above liimits

Semicoke – retorting waste, up to 10% organics, phenols, PAHs – hazardous waste

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OS ash produced

OS ash used

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2011-

2015

2016

2017

2018

2019

2020

ASH WASTE - ALKALINITY

• High alkalinity, pH 12–13 of transport and leachate waters. Controlled by portlandite and ettringite.
• Limited stabilization of plateau sediments by carbonation,

secondary reactions. High alkalinity potential remains for

a long time.

• Theoretical calculations show that full neutralization (pH 7)

of 1 m3 of ash sediment requires rainwater of 400 k years.

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LEGACY of OIL SHALE INDUSTRY

Land subsidence

LEGACY of OIL SHALE INDUSTRY

Land excavating

LEGACY of OIL SHALE INDUSTRY

Groundwater

LEGACY of OIL SHALE INDUSTRY

Land reclamation