页岩油
After Estonia gained independence, the state owned oil shale enterprise, Riigi Põlevkivitööstus (), was established as a department of the Ministry for Trade and Industry on 24 November 1918. Shale oil production started in Estonia in 1921 when Riigi Põlevkivitööstus built 14 experimental oil shale processing retorts in Kohtla-Järve. These vertical retorts used the method developed by Julius Pintsch AG that would later evolve into the current Kiviter processing technology. Along with the shale oil extraction plant, an oil shale research laboratory was founded in 1921. Following the experimental retorts, the first commercial shale oil plant was put into operation on 24 December 1924. This is considered as a beginning of the history of Viru Keemia Grupp.