In Poland, brown coal deposits occur in younger geological formations, mainly of the Tertiary age. Older brown coal deposits are known to occur also in the Jurassic, Carboniferous and rarely - Cretaceous and Triassic. The brown coals are intermediate in the qualification between hard coal and peat. Their characteristics and properties were markedly influenced by the type of the parent plant material and environment in which they originated.
Brown coal deposits originated both in platform areas and sedimentary basins in orogenic belts. The coals form the extensive seams from a few meters to several dozen meters in thickness. It also occur in the form of lenses. The thickness of overburden is usually quite small which makes the opencast mining of the deposits possible. Seams of older brown coals are often situated too deep below the surface level for the opencast mining and require the underground mining. This is also the case of coal seams occurring in glacitectonic folds. The methods of the underground mining were lately used in Poland to mine coals in Babina and Sieniawa deposits.
There is brown coal deposits occurrying in Poland presented on the map.
Brown coal resources are documented with taking into account the following limit values of the parameters that define the deposit for the opencast mining: the maximum depth of deposit base of 350 m, the minimum brown coal layer thickness in bed of 3 m and the maximum ratio of overburden and intercalation sum/deposit thickness of 12:1. The minimum weighted-average calorific value in a bed (with intercalations) should equal 6.5 MJ/kg (at the brown coal humidity of 50%). These are the basic criteria of geological-mining parameters and qualitative parameters for energy coals which are common in Polish deposits – typical ortholignites.
Poland’s anticipated economic resources of brown coal amounted to 23,261.83 million tonnes as of the end of 2019. The majority of resources – that is 23,261.19 million tonnes – constitute energy coals, remaining 0.64 million tonnes are bituminous coals (documented in Kaławsk-szyb główny deposit). There were also coals usable for the production of briquettes and coals suitable for the production of coal tar and liquid through a distillation documented in the past. Currently, all these coals are used and treated as energy coals only.
Table 1 shows resources and the current state of the exploration and development of brown coal deposits in Poland.
The anticipated economic resources within exploited deposits amounted to 1,170.81 million tonnes and accounted for 5.03% of total anticipated economic resources. Brown coal is being exploited in Poland by five mines: Bełchatów, Turów, Adamów, Konin and Sieniawa.
About 22% (5,185.33 million tonnes) of anticipated economic resources constitute the resources of the deposits within the Poznań through. These are Czempin, Gostyń, Krzywin and Mosina deposits where potentially strip mining is nowadays precluded on the environmental grounds and in the connection with large scale of production farms. These are the main issues to be solved by the local societies, the ecological organizations and the supporters of the deposits development, before the exploitation starts. It might seriously complicate the deposit development in the future.
Table 2 shows basic parameters of non-exploited deposits with anticipated economic resources exceeding 75 million tonnes.
The anticipated economic resources of brown coal amounted to 23,261.83 million tonnes in 2019 and decreased by 53.69 million tonnes (it means by 0.23%) in comparison with the previous year. The resources drop was mainly the result of the exploitation but also of the exploitation losses and of the declines/growths coming from the better deposit exploration which are showed by concession holders in their reports (and in their inventories of mineral deposit resources).
Economic resources of brown coal amounted to 994.55 million tonnes as of 31.12.2019 and decreased by 53.05 million tonnes (5.06%) in comparison with 2018. The economic resources changes were caused mainly by the output and by resources declines coming from the losses and from the better exploration. Such changes are reported by concession holders in the reports.
The brown coal output, according to the data provided by the concession holders, decreased in 2019 by 8,289 thousand tonnes (13.56%) in comparison with the previous year and amounted to 52,855 thousand tonnes. The exploitation was carried out in 8 deposits, there was no output recorded for Sieniawa 1 deposit. The majority of the output came from the outcrops exploited by PGE GiEK join-stock Company, especially from Bełchatów-pole Szczerców deposit (36,414 thousand tonnes, which accounted for 68.89% of the domestic production). In 2018, the percentage was much lower – that is 56.66%. The gradually increasing output from the Szczerców field compensates the depletion of the Bełchatów field allowing to maintain the stable level of the exploitation for the Bełchatów power station. The output from Bełchatów-pole Bełchatów deposit amounted to only 4,374 thousand tonnes (8.28% of the domestic output). The output from Turów deposit was equal 5,018 thousand tonne (9.49% of the domestic output). The exploitation level in deposits located in the Konin area (to the needs of ZE PAK join-stock Company) amounted to: Tomisławice deposit – 2,329 thousand tonnes (4.41% of the domestic output); Pątnów IV – 2,214 thousand tonnes (4.19%), Drzewce – 1,313 thousand tonnes (2.48%) and Adamów – 895 thousand tonnes (1.69%). The remaining output came from Sieniawa 2 deposit and was equal 296 thousand tonnes (0.56% of the domestic output). In comparison with 2018, the brown coal output increased in four deposits: - by 1,770 thousand tonnes (5.11%) from Bełchatów-pole Szczerców deposit; - by 627 thousand tonnes (36.84%) from Tomisławice deposit; - by 236 thousand tonnes (almost fivefold – as a result of sale to ZE PAK join-stock Company) from Sieniawa 2 deposit; - by 99 thousand tonnes (12.44%) from Adamów deposit. In other deposits, there were the output drops recorded – the most significant for Bełchatów-pole Bełchatów deposit amounted to 7,806 thousand tonnes (64.09%); for Turów deposit it was 1,575 thousand tonnes (23.89%); for Pątnów IV deposit 957 thousand tonnes (30.18%); for Drzewce deposit 633 thousand tonnes (32.53%).
The Energy Policy of Poland 2030 indicated Legnica, Gubin and satellite deposits of operating mines as provided for the exploitation till 2030. Updated, governmental project of The Energy Policy of Poland till 2040 (issued on 08.11.2019) recognized Złoczew and Ościsłowo deposits as prospective, whereas Gubin deposit as reserve (de facto it did not indicate which one of: Gubin, Gubin 1, Gubin 2, Gubin – Zasieki – Brody deposits listed in Table 3 is recognized as reserve).
Even though the governmental documents predict the potential exploitation of only several deposits for energy production, they do not exclude the deposits development to other needs, especially the chemical processing. For such purpose, there should be brown coal occurrences identified at the depth exceeding 350 m taken into account. They have not been the subject of documentation so far due to the recommended limit values of the parameters that define the deposit for the opencast mining. The greater bedding depth is beneficial in terms of the underground gasification, but on the other hand the gasification process can be hampered by the hydrogeological conditions. Nevertheless, to start such exploitation, there must be redefined and formalized new balancing criteria and brand new documentation works have to be carried out – in the first place in the Ścinawa-Głogów prospective area with significant brown coal resources, in which most of the coal beds occur deep. The second potential region is the area of Pyrzyce and Myślibórz vicinities (Zachodniopomorskie Voivodeship) with the Cenozoic base bedding deep.
The potential extension of the brown coal resources base, in terms of the traditional opencast mining, is in particular connected with the formalization (the geological documentation in D category) of the already known brown coal occurrences for which the documentation has not been elaborated due to the low degree of the geological exploration. According to the current data, the Polish prognostic brown coal resources with potential balancing features amount to 18,251.79 mln tonnes*).
The figure shows changes in the resources and production of brown coal in Poland in the years 1989-2019.
In the Table 3 given below there is the state of resources exploration, the state of deposits development along with the output volumes presented for the whole country.
Prepared by: Sławomir Mazurek, Marcin Tymiński
* Kasiński J.R., Mazurek S., Młynarczyk M., 2020 - Węgiel brunatny (brown coal). In: Bilans perspektywicznych zasobów kopalin Polski wg stanu na 31.12.2018 r. (eds. Szamałek K., Szuflicki M., Mizerski W.): 84-98. PIG-PIB, Warszawa.