The county’s chemical industry was founded soon after mining of the most important local natural resource – oil shale – began.
In the year 1921 a pilot oil factory was started in Kohtla-Järve where oil shale retorting for the purpose of obtaining oil was tested in a special retort, i.e. oil shale was heated anaerobically.
As the results were far better than had been expected, four oil factories were built in the years 1924-1942. The products of the retorting were marketed as heating and impregnating oil, bitumen and motor fuel. Oil shale gas was burned in the company’s own power station.
In the year 1928 oil shale retorting was also begun in Kiviõli. Whereas in Kohtla Järve so-called gas generators were used for retorting, in Kiviõli preference was given to tunnel furnaces until the year 1953. Later also an oil factory with gas generators was opened, and tests with a pilot device employing a solid heat-carrying agent were launched.
In 1945, by resolution of the then State Defence Committee of the USSR, the construction of a new oil shale processing complex was begun in Kohtla-Järve under the slogan “Gas for Leningrad”.
From 1948 domestic gas, manufactured from oil shale, was pumped to Leningrad. Later the gas pipeline was also directed to Tallinn and other North Estonian cities.
In 1962 the first tonnes of benzene and toluene were produced in Kohtla-Järve from the gas-naphta formed during gas cleaning. The list of products came to include urea resins, which were no longer based on oil shale, but instead on imported raw material. Large and state-of-the-art formalin and benzoic acid production units were launched. In addition, a high-capacity sulphuric acid shop using imported sulphur as its raw material was built and launched.
In 1968 a nitrogen fertilisers plant was constructed in Kohtla-Järve. It had initially been planned for oil shale gas to be used as the raw material, but in economic terms natural gas was more expedient. With the advent of natural gas in the chemical industry, the importance of oil shale as a raw material decreased. The gradual phasing out of the oil shale gas plant began at this time, and it was finally closed in the 1980s.
At present Viru Keemia Grupp (VKG) administrates the oil shale processing complex.