Keywords
critical raw materials
exploratory data analysis
municipal solid waste incineration
sustainable circular economy
How to Cite
Abstract
Urban mining increasingly concentrates on secondary raw materials derived from waste streams, among which municipal solid waste incineration (MSWI) residues are of growing importance. Fly ash, in particular, contains a wide range of trace and critical elements, yet its variability and internal associations remain insufficiently characterised. In the present study, 30 fly ash samples were collected in 2021 on a weekly basis from an MSWI facility in southern Poland. Eighteen elements (Ag, Al, Au, Ba, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Pt, Sb, Sr, V and Zn) were quantified using ICPMS and ICP-OES, producing a robust dataset suitable for multivariate analysis. Data exploration comprised descriptive statistics, normality assessment with the Shapiro-Wilk test, outlier detection via Rosner’s test, correlation analysis using Pearson’s and Spearman’s coefficients, and hierarchical cluster analysis (HCA). Results show that most elements display moderate concentrations (10–1000 ppm), while Al, Fe, and Zn exceed 1000 ppm, and noble metals remain below 10 ppm. Strong positive correlations were observed between Sr and Li, as well as Fe, Ni, and Mo, while HCA consistently grouped Cr, Fe, Mo, and Ni into a stable cluster across methods. The most accurate dendrogram structure was achieved with average linkage (Euclidean or Manhattan), whereas Pearson-based distances produced sharper cluster boundaries. Importantly, the elemental concentrations determined in fly ash were systematically compared with both the geochemical background of the Earth’s crust and typical grades in natural ore deposits. This comparison revealed substantial enrichment in Zn, Pb, Sb, Ag, Au, and Pt relative to crustal averages, while only Zn (and occasionally Cu and Ag) reached concentrations approaching the lower thresholds of economically exploited ore deposits. These findings demonstrate the internal geochemical structure of MSWI fly ash and underscore its significance as a potential source of valuable elements within the framework of urban mining.
References
Assi A., Bilo F., Zanoletti A., Ponti J., Valsesia A., La Spina R., Zacco A. & Bontempi E., 2020. Zero-waste approach in municipal solid waste incineration: Reuse of bottom ash to stabilize fly ash. Journal of Cleaner Production 245, 118779. DOI: https://doi.org/10.1016/j.jclepro.2019.118779
Bakalár T., Pavolová H., Hajduová Z., Lacko R. & Kyšeľa K., 2021. Metal recovery from municipal solid waste incineration fly ash as a tool of circular economy. Journal of Cleaner Production 302, 126977. DOI: https://doi.org/10.1016/j.jclepro.2021.126977
British Geological Survey, 2025. Minerals UK. website: https://Www.Bgs.Ac.Uk/Mineralsuk// (accessed on 20.08.2025).
Buha J., Mueller N., Nowack B., Ulrich A., Losert S. & Wang J., 2014. Physical and chemical characterization of fly ashes from Swiss waste incineration plants and determination of the ash fraction in the nanometer range. Environmental Science & Technology 48, 4765–4773.
Fabricius A.L., Renner M., Voss M., Funk M., Perfoll A., Gehring F., Graf R., Fromm S. & Duester L., 2020. Municipal waste incineration fly ashes: from a multi-element approach to market potential evaluation. Environmental Sciences Europe 32, 88.
Funari V., Toller S., Vitale L., Santos R.M. & Gomes H.I., 2023. Urban mining of municipal solid waste incineration (MSWI) residues with emphasis on bioleaching technologies: a critical review. Environmental Science and Pollution Research 30, 59128–59150.
Fuoco R., Ceccarini A., Tassone P., Wei Y., Brongo A. & Francesconi S., 2005. Innovative stabilization/solidification processes of fly ash from an incinerator plant of urban solid waste. Microchemical Journal 79, 29–35. DOI: https://doi.org/10.1016/j.microc.2004.10.011
Haberl J. & Schuster M., 2019. Solubility of elements in waste incineration fly ash and bottom ash under various leaching conditions studied by a sequential extraction procedure. Waste Management 87, 268–278.
Hand D.J., Smyth P. & Mannila H., 2001. Principles of Data Mining. MIT Press, website:
Hauke J. & Kossowski T., 2011. Comparison of values of Pearson’s and Spearman’s correlation coefficients on the same sets of data. Quaestiones Geographicae 30, 87–93. DOI: https://doi.org/10.2478/v10117-011-0021-1
Headrick T.C., 2016. A note on the relationship between the Pearson product-moment and the Spearman rank-based coefficients of correlation. Open Journal of Statistics 06(06). DOI: https://doi.org/10.4236/ojs.2016.66082
Huang S.C., Chang F.C., Lo S.L., Lee M.Y., Wang C.F. & Lin J.D., 2007. Production of lightweight aggregates from mining residues, heavy metal sludge, and incinerator fly ash. Journal of Hazardous Materials 144, 52–58. DOI: https://doi.org/10.1016/j.jhazmat.2006.09.094
Ilyushechkin A., He C. & Hla S.S., 2020. Characteristics of inorganic matter from Australian municipal solid waste processed under combustion and gasification conditions. Waste Management & Research 39, 928–936. DOI: https://doi.org/10.1177/0734242X20966655
Işıldar A., Ren E.R., van Hullebusch E.D. & Lens P.N.L., 2018. Electronic waste as a secondary source of critical metals: Management and recovery technologies. Resources, Conservation and Recycling 135, 296–312. DOI: https://doi.org/10.1016/j.resconrec.2017.07.031
Ivan Diaz-Loya E., Allouche E.N., Eklund S., Joshi A.R. & Kupwade-Patil K., 2012. Toxicity mitigation and solidification of municipal solid waste incinerator fly ash using alkaline activated coal ash. Waste Management 32, 1521–1527. DOI: https://doi.org/10.1016/j.wasman.2012.03.030
Joseph A., Snellings R., Van den Heede P., Matthys S. & De Belie N., 2018. The use of municipal solid waste incineration ash in various building materials: A Belgian point of view. Materials 11, 141. DOI: https://doi.org/10.3390/ma11010141
Kabata-Pendias A., 2011. Trace Elements in Soils and Plants (4th ed.). CRC Press, website: DOI: https://doi.org/10.1201/b10158
Kalmykova Y. & Karlfeldt Fedje K., 2013. Phosphorus recovery from municipal solid waste incineration fly ash. Waste Management 33, 1403–1410. DOI: https://doi.org/10.1016/j.wasman.2013.01.040
Kanhar A.H., Chen S. & Wang F., 2020. Incineration fly ash and its treatment to possible utilization: A review. Energies 13, 6681. DOI: https://doi.org/10.3390/en13246681
Kara F., 2021. Comparison of tree diameter distributions in managed and unmanaged Kazdaği fir forests. Silva Balcanica 22, 31–43. DOI: https://doi.org/10.3897/silvabalcanica.22.e58020
Kravtsova M.V. & Volkov D.A., 2015. Methodology of research for qualitative composition of municipal solid waste to select an optimal method of recycling. IOP Conference Series: Materials Science and Engineering 91, 012075. DOI: https://doi.org/10.1088/1757-899X/91/1/012075
Lane D.J., Hartikainen A., Sippula O., Lähde A., Mesceriakovas A., Peräniemi S. & Jokiniemi J., 2020. Thermal separation of zinc and other valuable elements from municipal solid waste incineration fly ash. Journal of Cleaner Production 253, 120014. DOI: https://doi.org/10.1016/j.jclepro.2020.120014
Lima A.T., Ottosen L.M., Pedersen A.J. & Ribeiro A.B., 2008. Characterization of fly ash from bio and municipal waste. Biomass and Bioenergy 32, 277–282. DOI: https://doi.org/10.1016/j.biombioe.2007.09.005
Mudd G.M., Jowitt S.M. & Werner T.T., 2017. The world’s lead-zinc mineral resources: Scarcity, data, issues and opportunities. Ore Geology Reviews 80, 1160–1190. DOI: https://doi.org/10.1016/j.oregeorev.2016.08.010
Murtagh F. & Contreras P., 2011. Methods of hierarchical clustering. Computing Research Repository – CORR. DOI: https://doi.org/10.1007/978-3-642-04898-2_288
Nielsen F., 2016. Hierarchical clustering. [In:] Introduction to HPC with MPI for data science. Springer International Publishing, 195–211. DOI: https://doi.org/10.1007/978-3-319-21903-5_8
PN-EN 14899: 2006. Polski Komitet Normalizacyjny, 2006. PN-EN 14899 Charakteryzowanie odpadów – Pobieranie próbek materiałów – Struktura przygotowania i zastosowania planu pobierania próbek [Characterization of waste – Sampling of waste materials – Framework for the preparation and application of a sampling plan].
Prasittisopin L., 2024. Power plant waste (fly ash, bottom ash, biomass ash) management for promoting circular economy in sustainable construction: emerging economy context. Smart and Sustainable Built Environment, website DOI: https://doi.org/10.1108/SASBE-09-2024-0395
Rosner B., 1983. Percentage Points for a Generalized ESD Many-Outlier Procedure. Technometrics 25, 165–172. DOI: https://doi.org/10.1080/00401706.1983.10487848
Rudnick R.L. & Gao S., 2003. Composition of the continental crust. Treatise on Geochemistry 3, 1–64. DOI: https://doi.org/10.1016/B0-08-043751-6/03016-4
Rusănescu C.O. & Rusănescu M., 2023. Application of fly ash obtained from the incineration of municipal solid waste in agriculture. Applied Sciences 13, 3246. DOI: https://doi.org/10.3390/app13053246
Schlumberger S. & Bühler J., 2012. Urban mining: Metal recovery from fly and filter ash in waste to energy plants. Ash Utilisation 2012 − Ashes in a Sustainable Society. Stockholm, Sweden.
Shapiro S.S. & Wilk M.B., 1965. An analysis of variance test for normality (complete samples). Biometrika 52, 591. DOI: https://doi.org/10.2307/2333709
Singer D.A., Berger V.I. & Moring B.C., 2008. Porphyry copper deposits of the world: Database and grade and tonnage models. website: https://Pubs.Usgs.Gov/of/2008/1155/ (accessed on: 20.08.2025).
Sobianowska-Turek A., 2018. Hydrometallurgical recovery of metals: Ce, La, Co, Fe, Mn, Ni and Zn from the stream of used Ni-MH cells. Waste Management 77, 213–219. DOI: https://doi.org/10.1016/j.wasman.2018.03.046
Sokal R.R. & Rohlf F.J., 1962. The comparison of dendrograms by objective methods. Taxon 11, 33–40.
Tang J. & Steenari B.M., 2015. Solvent extraction separation of copper and zinc from MSWI fly ash leachates. Waste Management 44, 147–154. DOI: https://doi.org/10.1016/j.wasman.2015.07.028
U.S. Geological Survey, 2021. 2021 Minerals Yearbook. website: https://Pubs.Usgs.Gov (accessed on 20.08.2025).
U.S. Geological Survey, 2024. Mineral Commodity Summaries. website: https://Pubs.Usgs.Gov/Periodicals/Mcs2024 (accessed on 20.08.2025).
Valero A. & Valero A., 2014. Thanatia: the destiny of the Earth’s mineral resources. A thermodynamic cradle to cradle assessment. World Scientific, Singapore, 629 pp.
Wang P., Li J., Hu Y. & Cheng H., 2023. Solidification and stabilization of Pb–Zn mine tailing with municipal solid waste incineration fly ash and ground granulated blast-furnace slag for unfired brick fabrication. Environmental Pollution 321, 121135. DOI: https://doi.org/10.1016/j.envpol.2023.121135
Wong S., Mah A.X.Y., Nordin A.H., Nyakuma B.B., Ngadi N., Ma, R., Amin N.A.S., Ho W.S. & Lee T.H., 2020. Emerging trends in municipal solid waste incineration ashes research: a bibliometric analysis from 1994 to 2018. Environmental Science and Pollution Research 27, 7757–7784. DOI: https://doi.org/10.1007/s11356-020-07933-y
Yakubu Y., Zhou J., Ping D., Shu Z. & Chen Y., 2018. Effects of pH dynamics on solidification/stabilization of municipal solid waste incineration fly ash. Journal of Environmental Management 207, 243–248. DOI: https://doi.org/10.1016/j.jenvman.2017.11.042
Zierold K.M. & Odoh C., 2020. A review on fly ash from coal-fired power plants: chemical composition, regulations, and health evidence. Reviews on Environmental Health 35, 401–418. DOI: https://doi.org/10.1515/reveh-2019-0039
License
Copyright (c) 2025 Barbara Bielowicz, Monika Chuchro
This work is licensed under a Creative Commons Attribution 4.0 International License.