eesti teaduste
akadeemia kirjastus
SINCE 1984
Oil Shale cover
Oil Shale
ISSN 1736-7492 (Electronic)
ISSN 0208-189X (Print)
Impact Factor (2021): 1.442
Comparison of the ecotoxic properties of oil shale industry by-products to those of coal ash; pp. 1–19
PDF | 10.3176/oil.2022.1.01

Heidi Lees, Oliver Järvik, Alar Konist, Andres Siirde, Birgit Maaten

The European Union (EU) presented a uniform List of Waste (LoW) in 2000 and last updated the technical guidance in 2018. The respective local regulations for the classification of waste in Estonia were set in 2015. Due to the changes in the regulations, it was necessary to review the properties of solid wastes generated in Estonian oil shale industry in light of hazardous properties. Therefore, the properties of the produced ash streams were analysed and the obtained results were compared to those for coal for being in accordance with common practices. The main objective of the paper was to answer the question whether the properties of oil shale (OS) are comparable to those of coal as coal and its combustion residues were not considered hazardous waste in Europe, but the respective counterparts of oil shale were. The EU guidelines suggest the use of calculations based on trace element concentrations for the classification of hazardous property (HP) 14 – ecotoxic. Therefore, an extensive study was conducted to investigate the hazardous properties of all the solid residues from power plants operating on oil shale and shale oil production facilities. This paper describes one part of it – the trace element compositions of the major ash streams produced in the Estonian oil shale industry and focuses on their comparison with data available for coal ash samples. The findings of the study showed that, similarly to coal, oil shale ash (OSA) should not be considered as ecotoxic due to the low concentrations of trace elements. It was found that the investigated oil shale ash samples exhibited a very similar composition and properties to those of coal, and as a result of a larger study, from the beginning of 2020, oil shale ash and other oil shale thermal treatment residues are not classified as hazardous waste in Estonia, thereby initiating policy changes that affect most areas of the economy.


1. Siirde, A. Oil shale – global solution or part of the problem? Oil Shale, 2008, 25(2), 201–202.

2. Paiste, P., Külaviir, M., Paaver, P., Heinmaa, I., Vahur, S., Kirsimäe, K. Benefi-ciation of oil shale processing waste: secondary binder phases in alkali activated composites. Waste Biomass Valori., 2019, 10(5), 1407–1417.

3. Maaten, B., Konist, A., Siirde, A. High-speed thermogravimetric analysis of the combustion of wood and Ca-rich fuel. J. Therm. Anal. Calorim., 2019, 138(4), 2807–2811.

4. Irha, N., Reinik, J., Jefimova, J., Koroljova, A., Raado, L.-M., Hain, T., Uibu, M., Kuusik, R. PAHs in leachates from thermal power plant wastes and ash-based construction materials. Environ. Sci. Pollut. Res., 2015, 22(15), 11877–11889.

5. Kaljuvee, T., Trass, O., Pihu, T., Konist, A., Kuusik, R. Activation and reactivity of Estonian oil shale cyclone ash towards SO2 binding. J. Therm. Anal. Calorim., 2015, 121(1), 19–28.

6. Apithanyasai, S., Supakata, N., Papong, S. The potential of industrial waste: using foundry sand with fly ash and electric arc furnace slag for geopolymer brick production. Heliyon, 2020, 6(3), e03697.

7. Taulbee, D. N., Graham, U. M., Carter, S. D., Robl, T. L., Derbyshire, F. Exami-nation of eastern US oil shale by-products and their markets. Fuel, 1995, 74(8), 1118–1124.

8. Akar, A., Ekinci, E. Production of chemicals from oil shales. Fuel, 1995, 74(8), 1113–1117.

9. Külaots, I., Goldfarb, J. L., Suuberg, E. M. Characterization of Chinese, American and Estonian oil shale semicokes and their sorptive potential. Fuel, 2010, 89(11), 3300–3306.

10. Pototski, A. Estonian Environmental Strategy, 2013 (in Estonian).

11. ASTM International, “ASTM D388-19a, Standard Classification of Coals by Rank,” West Conshohocken, PA, 2019.

12. European Commission. Regulation (EC) No. 1357/2014 of 18 December 2014 Replacing Annex III to Directive 2008/98/EC of the European Parliament and the Council on Waste and Repealing Certain Directives. 2014.

13. Tallinn University of Technology and University of Tartu. Potential Hazardousness of Estonian Oil Shale Ashes, Tallinn, 2019, 1–184 (in Estonian).

14. Lecomte, T., Ferreria De La FuenteJ., Neuwahl, F., Canova, M., Pinasseau, A., Jankov, I., Brinkmann, T., Roudier, S., Delgado Sancho, L. Best Available Techniques (BAT) Reference Document for Large Combustion Plants. Publications Office of the European Union, Luxembourg, 2017.

15. Environmental Protection Agency. Hazardous and Solid Waste Management System: Disposal of Coal Combustion Residuals from Electric Utilities; Amendments to the National Minimum Criteria (Phase One, Part One), 2018, 36435–36456.

16. Heidrich, C., Feuerborn, H.-J., Weir, A. Coal combustion products: a global perspective. In: World of Coal Ash (WOCA) Conference, 22–25 April 2013, Lexington, KY.

17. European Commission. Commission Notice on Technical Guidance on the Classification of Waste. Official Journal of the European Union, OJ C 124, 9.4.2018, 1–134.

18. The European Parliament and the Council of the European Union. Council Regulation (EU) 2017/997 amending Annex III to Directive 2008/98/EC of the European Parliament and of the Council as regards the hazardous property HP 14 ‘Ecotoxic’. 2017, 1–4.

19. Hennebert, P., Humez, N., Conche, I., Bishop, I., Rebischung, F. Assessment of four calculation methods proposed by the EC for waste hazardous property HP 14 ‘Ecotoxic’. Waste Manage., 2016, 48, 24–33.

20. Pihu, T., Konist, A., Puura, E., Liira, M., Kirsimäe, K. Properties and environ-mental impact of oil shale ash landfills. Oil Shale, 2019, 36(2), 257–270.

21. Arro, H., Prikk, A., Pihu, T., Öpik, I. Utilization of semi-coke of Estonian shale oil industry. Oil Shale, 2002, 19(2), 117–125.

22. Plamus, K., Soosaar, S., Ots, A., Neshumayev, D. Firing Estonian oil shale of higher quality in CFB boilers – environmental and economic impact. Oil Shale, 2011, 28(1S), 113–126.

23. Konist, A., Pihu, T., Neshumayev, D., Siirde, A. Oil shale pulverized firing: boiler efficiency, ash balance and flue gas composition. Oil Shale, 2013, 30(1), 6–18.

24. Hotta, A., Parkkonen, R., Hiltunen, M., Arro, H., Loosaar, J., Parve, T., Pihu, T., Prikk, A., Tiikma, T. Experience of Estonian oil shale combustion based on CFB technology at Narva power plants. Oil Shale, 2005, 22(4S), 381–397.

25. Ots, A. et al. Influence of Oil Shale Composition to the Technical-Economical Indicators and Emissions of Energy Unit with CFBC Boilers, 2008 (in Estonian).

26. Pihu, T., Konist, A., Neshumayev, D., Loosaar, J., Siirde, A., Parve, T., Molodtsov, A. Short-term tests on firing oil shale fuel applying low-temperature vortex technology. Oil Shale, 2012, 29(1), 3–17.

27. Tsiridis, V., Petala, M., Samaras, P., Kungolos, A., Sakellaropoulos, G. P. Environmental hazard assessment of coal fly ashes using leaching and ecotoxicity tests. Ecotoxicol. Environ. Saf., 2012, 84, 212–220.

28. Baba, A., Kaya, A. Leaching characteristics of solid wastes from thermal power plants of western Turkey and comparison of toxicity methodologies. J. Environ. Manage., 2004, 73(3), 199–207.

29. Millemann, R. E., Parkhurst, B. R. Comparative toxicity of solid waste leachates to Daphnia magnaEnviron. Int., 1980, 4(3), 255–260.

30. Suloway, J. J., Skelly, T. M., Roy, W. R., Dickerson, D. R., Schuller, R. M., Griffin, R. A. Chemical and Toxicological Properties of Coal Fly Ash. Environmental Geology Notes 105 (Illinois State Geological Survey Division), 1983.

31. Neufeld, R. D., Wallach, S. Chemical and toxicity analysis of leachates from coal conversion solid wastes. J. Water Pollut. Control Fed., 1984, 56(3, Part I), 266–273.

32. Palumbo, A. V., Tarver, J. R., Fagan, L. A., McNeilly, M. S., Ruther, R., Fisher, L. S., Amonette, J. E. Comparing metal leaching and toxicity from high pH, low pH, and high ammonia fly ash. Fuel, 2007, 86(10–11), 1623–1630.

33. Bushumov, SA., Korotkova, TG., Ksandopulo, SJ., Solonnikova, NV., Demin, VI. Determination of the hazard class of ash after coal combustion by the method of biotesting. Orient. J. Chem., 2018, 34(1), 276–285.

34. Gallardo, S., van Hullebusch, ED., Pangayao, D., Salido, BM., Ronquillo, R. Chemical, leaching, and toxicity characteristics of coal ashes from circulating fluidized bed of a Philippine coal-fired power plant. Water Air Soil Pollut., 2015, 226(9), 312.

35. Skodras, G., Grammelis, P., Prokopidou, M., Kakaras, E., Sakellaropoulos, G. Chemical, leaching and toxicity characteristics of CFB combustion residues. Fuel, 2009, 88(7), 1201–1209.

36. Grammelis, P., Skodras, G., Prokopidou, M., Delvinquier, V., Lial, B., Kakaras, E., Sakellaropoulos, G. Investigations on the operating performance and ash toxicity of CFBC with imported coals. In: Proceedings of the 9th International Conference on Circulating Fluidized Beds, May 13–16, 2008, Hamburg, Germany, 1150.

37. Schwartz, GE., Hower, JC., Phillips, AL., Rivera, N., Vengosh, A., Hsu-Kim, HRanking coal ash materials for their potential to leacharsenic and seleniumRelative importance of ash chemistry and site biogeochemistry. Environ. Eng. Sci., 2018, 35(7), 728–738.

38. Arro, H., Prikk, A., Pihu, T. Calculation of qualitative and quantitative composition of Estonian oil shale and its combustion products. Part 2. Calculation on the basis of technical analysis data. Fuel, 2003, 82(18), 2197–2204.

39. Aunela-Tapola, LA., Frandsen, FJ., Häsänen, EK. Trace metal emissions from the Estonian oil shale fired power plant. Fuel Process. Technol., 1998, 57(1), 1–24.

40. Estonian Ministry of the Environment. National Development Plan for the Use of Oil Shale 2016–2030 - Report of 2016 and 2017. Tallinn, 2019 (in Estonian).

41. Lees, H., Järvik, O., Konist, A., Siirde, A., Maaten, B. Computational results of the ecotoxic analysis of fly and bottom ash from oil shale power plants and shale oil production facilities. Chem. Eng. Trans., 2020, 81, 967–972.

42. Koukouzas, N., Ketikidis, C., Itskos, G. Heavy metal characterization of CFB-derived coal fly ash. Fuel Process. Technol., 2011, 92(3), 441–446.

43. Maaten, B., Konist, A., Siirde, A. Potential of solid residues from power plants as thermochemical energy storage materials. J. Therm. Anal. Calorim., 2020, 142(5), 1799–1805.

44. Arro, H., Pihu, T., Prikk, A., Rootamm, R., Konist, A. Comparison of ash from PF and CFB boilers and behaviour of ash in ash fields. In: Proceedings of the 20th International Conference on Fluidized Bed Combustion (Yue, G., Zhang, H., Zhao, C., Luo, Z., eds.), Springer, Berlin, Heidelberg, 2009, 1054–1060.

45. Bityukova, L., Mõtlep, R., Kirsimäe, K. Composition of oil shale ashes from pulverized firing and circulating fluidized-bed boiler in Narva thermal power plants, Estonia. Oil Shale, 2010, 27(4), 339–353.

46. Reinik, J., Irha, N., Steinnes, E., Urb, G., Jefimova, J., Piirisalu, E. Release of 22 elements from bottom and fly ash samples of oil shale fueled PF and CFB boilers by a two-cycle standard leaching test. Fuel Process. Technol., 2014, 124, 147–154.

47. Kirso, U., Otson, R., Irha, N., Tanner, R., Tanner, H., Bogdanov, ASome ana-lytical problems concerning environment pollutants. Proc. Est. Acad. Sci. Chem., 1994, 43, 180–194.

48. Paalme, L., Voll, M., Urbas, E., Palvadre, R., Johannes, I., Kirso, U. Oil shale region influence on the atmospheric pollution of Lake Peipsi. Proc. Est. Acad. Sci. Chem., 1990, 39(1), 18–27 (in Estonian).

49. Kirso, U., Laja, M., Urb, G. Polycyclic aromatic hydrocarbons (PAH) in ash fractions of oil shale combustion: Fluidized bed vers pulverized firing. Oil Shale, 2005, 22(4S), 537–545.

50. Han, X., Külaots, I., Jiang, X., Suuberg, E. M. Review of oil shale semicoke and its combustion utilization. Fuel, 2014, 126, 143–161.

51. European Commission. “Regulation (EC) No 1907/2006 of the European Parliament and of the Council concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), establishing a European Chemicals Agency, amending Directive 1999/45/EC and repealing C,” Off. J. Eur. Union, vol. 49, 2006.

52. Regulation of the Government of the Republic of Estonia. Concentration limits for hazardous substances in soil. State Gaz. (Riigi Teataja), RT I 04.07.2019, 6 (in Estonian).

53. Loosaar, J., Parve, T., Konist, A. Environmental impact of Estonian oil shale CFB firing. In: Proceedings of the 20th International Conference on Fluidized Bed Combustion (Yue, G., Zhang, H., Zhao, C., Luo, Z., eds.), Springer, Berlin, Heidelberg, 2010, 422–428.

54. Kahru, U., Põllumaa, L. Environmental hazard of the waste streams of Estonian oil shale industry: An ecotoxicological review. Oil Shale, 2006, 23(1), 53–93.

55. Eurostat. Generation of Waste by Waste Category, Hazardousness and NACE Rev. 2 Activity, 2021.

56. European Commission. Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions - Closing the loop - An EU action plan for the Circular Economy, COM/2015/0614 final, 2015.

57. Commission Regulation (EU) No 1357/2014 of 18 December 2014 replacing Annex III to Directive 2008/98/EC of the European Parliament and of the Council on waste and repealing certain Directives. Official Journal of the European Union, OJ L 365, 19.12.2014, 89–96.

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