General information and occurrence
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 within sediments of platform areas and in sedimentary basins in orogenic belts. Coal forms extensive seams from a few meters to several dozen meters in thickness or occurs in the form of lenses. The thickness of overburden is usually quite small which makes the opencast mining of deposits possible. Seams of older brown coal 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 the Babina and Sieniawa deposits.
The brown coal deposits occurrence in Poland is presented on the map.
Brown coal resources are documented with taking into account the following limit values of the parameters that define the deposit and its boundaries for the opencast mining: the maximum depth of deposit base of 350 m, the minimum brown coal layer thickness in a 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. For the purposes of the underground gasification or the production of liquid fuels in the ground installations (mentioned in the Energy Policy of Poland 2040) the limit values of the parameters that define the deposit and its boundaries (balancing criteria) have not been established.
Resources and output
Domestic anticipated economic resources of brown coal in Poland amounted to 23,084.83 million tonnes as of the end of 2022. The majority of resources – that is 23,084.19 million tonnes – constitute energy coals, remaining 0.64 million tonnes are bituminous coals (documented in C2 category in the 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 only as energy coals.
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 in 2022 to 982.48 million tonnes and accounted for 4.26% of total anticipated economic resources. Brown coal from these deposits was exploited by 4 mines: Bełchatów, Turów, Konin and Sieniawa. The exploitation from the Drzewce deposit (in KWB Konin S.A. Company) ended in 2022.
More than 22% (5,185.33 million tonnes) of the brown coal anticipated economic resources constitute the resources of the deposits within the so-called Poznań through. These are the Czempin, Gostyń, Krzywin and Mosina deposits where potentially strip mining is nowadays precluded due to the environmental protection (surface) and in the connection with a 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 23,084.83 million tonnes as of the end of 2022 and decreased by 58.09 million tonnes (it means by 0.25%) in comparison with the previous year. The resources drop was mainly the result of the exploitation and the exploitation losses but also of the declines/growths coming from the better deposit exploration which are demonstrated by concession holders in their reports (mining reports of mineral deposit resources).
Economic resources of brown coal amounted to 819.39 million tonnes as of 31.12.2022 and decreased by 59.27 million tonnes (6.75%) in comparison with 2021. This change was caused by the output, the resources declines coming from the losses, the better deposits exploration during the exploitation and reclassification of the part of economic resources to the sub-economic resources within the Bełchatów-pole Bełchatów deposit. In 2022, there was not any new deposit development plan or a supplement to such a plan elaborated.
The brown coal output, according to the data provided by the concession holders, increased in 2022 by 2,828 thousand tonnes (that is by 5.16%) in comparison with the previous year and amounted to 57,679 thousand tonnes. The exploitation was carried out from 7 deposits, however from the Drzewce deposit the operation on the deposit ended in August 2022. The majority of the domestic output came from the outcrops exploited by the PGE GiEK join-stock Company, particularly from the Bełchatów-pole Szczerców deposit (40,735 thousand tonnes) which accounted for 70.62% of the domestic output (in 2020 and 2021, these percentage contributions were as follows – 71.16% and 69.19%, respectively). The gradually increasing output from the Szczerców field compensates the depletion of the Bełchatów field (3,524 thousand tonnes, that is 6.11% of the domestic output in 2022, with the percentage contributions equal 5.37% in 2020 and 5.27% in 2021) and allows to maintain the stable level of the exploitation for the Bełchatów power station. The output from the Turów deposit was equal 9,881 thousand tonnes (17.13% of the domestic output). The exploitation level from the deposits located in the Konin area (to the needs of the ZE PAK join-stock Company) amounted to: the Tomisławice deposit – 1,160 thousand tonnes (2.01% of the domestic output); the Drzewce deposit – 1,050 thousand tonnes (1.82%); the Pątnów IV deposit – 797 thousand tonnes (1.38%). The remaining output came from the Sieniawa 2 deposit and was equal 531 thousand tonnes (0.92% of the domestic output). In comparison with 2021, the brown coal output increased in 4 deposits: - by 2,782 thousand tonnes (7.33%) from the Bełchatów-pole Szczerców deposit; - by 1,054 thousand tonnes (11.94%) from the Turów deposit; - by 635 thousand tonnes (21.98%) from the Bełchatów-pole Bełchatów deposit; - by 172 thousand tonnes (47.91%) from the Sieniawa 2 deposit. In 3 remaining, exploited deposits, there were the output drops recorded – the most significant for the Tomisławice deposit amounted to 1,324 thousand tonnes (53.30%); for the Pątnów IV deposit it was 422 thousand tonnes (34.62%), whereas for the Drzewce deposit the exploitation level decreased by 10 thousand tonnes (0.94%).
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 1989-2022.
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.
Table 1. Brown coal - million tonnes