Waste of the past, resource of the future!
Natural resources are defined as natural assets (raw materials) occurring in nature that are susceptible to be used for economic production or consumption (UN, 1997). By 2050, humanity could consume an estimated 140 billion tonnes of natural resources unless the economic growth rate decoupled from the natural resource consumption rate (UNEP, 2011). 10 years have passed since this statement was published and the economic growth is still coupled to the natural resource use. Additionally, the clean energy transition is increasing the natural resource use, especially in metallic ores containing critical raw materials (European Commission, 2020), for the production of clean energy products.
Globally, the extraction and processing of natural resources account for around 50% of the total greenhouse gas emissions (IRP, 2019). Furthermore, over 90% of the ecological impacts on water-stress and biodiversity loss are resulting from the land-use for the extraction and processing of natural resources (IRP, 2019). Since 1970, the use of natural resources has more than tripled and continues to grow (IRP, 2019). Therefore, decoupling the natural resource use from the economic growth rate, while reducing the environmental and health impacts, is a must when shifting towards a sustainable future (UNEP, 2011) – Figure 1.
Figure 1. Decoupling natural resource use and environmental impacts from economic growth (UNEP, 2011)
According to IRP (2019), global material extraction rates are divided into the following categories of natural resources:
- Non-metallic minerals: sand, gravel, and clay deposits, represented 48% of global material extraction (43.8 billion tonnes);
- Biomass: crops, crop residues, grazed biomass, timber, and wild catch of fish, represented 26% of global material extraction (24.1 billion tonnes);
- Fossil fuels: coal, petroleum, natural gas, oil shale, and tard sands, represented 16% of global material extraction (15 billion tonnes);
- Metallic ores: iron, aluminium, copper, zinc, lead and tin ores, represented 10% of global material extraction (9.1 billion tonnes).
From 1970 to 2017, there was a major shift in global extraction from biomass to mineral-based natural resources (IRP, 2019). This transition, sparked by the urban-industrial economy, has been causing major environmental impacts, from a local to a global scale. Moreover, the waste generated by the extraction and processing of natural resources, especially non-ferrous metal ores, can represent not only an environmental and health hazard but also a resource loss due to their content in base, precious and critical metals that can be applied in several emergent technologies. Sulphidic mining waste, especially mine tailings from the processing plants, pose as a large challenge due to their content in hazardous metals (e.g. Cd, Cr, Pb), metalloids (e.g.: As, Sb) and non-metals (e.g. S), which tend to become more chemically available, leading to the generation of acid mine drainage (European Commission, n.d.).
In the EU-27, mining and quarrying waste from mineral deposits, in 2018, accounted for more than a quarter (26.2%) of all the waste output (Eurostat, n.d.) – Figure 2. In fact, after construction and demolition waste, mining and quarrying waste is considered as the biggest waste stream in the EU-27 (Eurostat, n.d.).
Figure 2. Waste generation by economic activities and households in the EU-27 as of 2018 (Eurostat, n.d.)
Apart from the hazardous metal, metalloid and non-metal content, this sulphidic mining waste contains considerable concentrations of ceramic-friendly minerals, such as quartz and phyllosilicates, which indicates that the mineral residues can potentially be used as alternative raw materials in different ceramic products.
Replacement of primary raw materials in ceramics (sand and clay) by alternative raw materials, such as mining waste, can contribute to minimising the pressure over the primary raw materials sector, as well as for the sustainable supply of raw materials within the EU, thus fastening the shift towards a more resource-efficient economy (European Commission, 2013). Furthermore, non-metallic mineral deposits, such as sandstones or clay mineral deposits, are the biggest share of global material extraction, which make alternative sources essential for a sustainable approach to global resource management.
Traditional ceramics tend to be manufactured from naturally occurring raw materials. Therefore, this industry has been exploiting mineral deposits, mainly clay mineral and sandstone, to produce traditional ceramic products, such as roof tiles, blocks, pavers, or facing bricks. These ceramic products are inorganic materials made of mainly non-metallic minerals, which are made permanent by a firing process. The ceramic industry is a resource-intensive, high-energy consumption and CO2 emission (mainly during the drying and firing) sector. Nevertheless, the final ceramic product’s properties include high-strength, weathering resistance, long service life, chemical inertness and non-toxicity, resistance to heat and fire, electrical resistance and, sometimes, specific porosity (European Commission, 2007).
Recent studies have proved that mining waste materials could be a potential ceramic resource:
- Roof tiles: a ceramic mixture with kaolin processing waste and granite sawing waste (up to 50 wt%) increased mechanical properties at low firing temperatures (Menezes et al., 2007);
- Blocks: ornamental rock waste mixed with clay has showed satisfying physical and chemical results for the manufacturing of traditional inner wall blocks (Cerqueira et al., 2016);
- Pavers: a ceramic mixture with ornamental rock beneficiation residues showed an increase in dry density, better sintering at higher temperatures (1050°C), as well as decreasing the water absorption values (Amaral et al., 2019);
- Bricks: incorporation of spodumene ore tailings in low-temperature ceramic bricks have shown compliance with product specifications (Lemougna et al., 2019).
Therefore, one of the EU H2020 MSCA-ITN-ETN SULTAN’s aim is to evaluate the potential replacement of primary raw materials (mainly clay and sand) in traditional ceramics by sulphidic mining waste materials from Belgium (Plombières inactive mine), Germany (Freiberg inactive mine) and Portugal (Neves Corvo active mine). A recently published research study has assessed the use of 4 different mining waste materials in ceramic mixtures for roof tiles and blocks (Veiga Simão et al., 2021).
The results of the study have shown that Plombières yellow tailing layer, being the most prominent layer of the tailing pond according to Bevandić et al. (2021), can be considered as the best fit to partially or totally replace primary raw materials (mainly clay and sand) in roof tile (5 wt%) and block (10 wt%) mixtures, taking into account production parameters, product quality, and environmental compliance. In fact, Plombières clayey-silt tailing doesn’t require any further mechanical pre-treatment such as the coarse Neves Corvo waste rock material need. The low sulphur and metal(loid) content in Plombières yellow tailing, in contrast with the high sulphur and metal(loid) content of Freiberg and Neves Corvo mining waste materials, makes the fired ceramic blends always comparable to the standard, with satisfying technical (modulus of elasticity, water absorption, drying and firing shrinkage), aesthetical (efflorescence and black core – Figure 3), and chemical (soluble sulphates) properties. Lastly, according to the Flemish environmental regulations for use of waste in or as building material (VLAREMA, 2012), both the Plombières tailing and Neves Corvo fresh waste rock proved to be suitable for use as a granular (non-shaped) building material.
Figure 3. Black core in roof tile test specimens (fired at 985°C)
The high sulphidic content and coarser grain size in some of the studied waste materials proved to be not suitable to replace primary raw materials in ceramic roof tiles and blocks. On the other hand, Plombières fine tailing material has shown that it can be a potential alternative source of raw materials for ceramics, even without any chemical and/or mechanical pre-treatment.
The technical and economic limitations on the recovery of these alternative raw materials can potentially be overcome with specific regulatory actions in this new market sector, thus boosting a resource-efficient economy by turning waste into a resource-opportunity for a more sustainable future.
References:
Amaral, L.F., Carvalho, J.P.R.G., Silva, B.M., Delaqua, G.C.G., Monteiro, S.N., Vieira, C.M.V., 2019. Development of ceramic paver with ornamental rock waste. Journal of Materials Research and Technology, Volume 8, Issue 1, pp. 599-608. DOI: https://doi.org/10.1016/j.jmrt.2018.05.009
Bevandić, S., Blannin, R., Vander Auwera, J., Delmelle, N., Caterina, D., Nguyen, F., Muchez, P, 2021. Geochemical and Mineralogical Characterisation of Historic Zn–Pb Mine Waste, Plombières, East Belgium. Minerals, 11(1), 28. DOI: https://doi.org/10.3390/min11010028
Cerqueira, N.A., Choe, D., Alexandre, J., Azevedo, A.R.G., Xavier, C.G., Souza, V.B., 2016. Properties of clay for ceramics with rock waste for production structural block by pressing and firing. In Ikhmayies S.J. et al. (eds) Characterization of Minerals, Metals, and Materials 2016, pp. 653-659. Springer, Cham. DOI: https://doi.org/10.1007/978-3-319-48210-1_82
European Commission, 2007. Best Available Techniques in the Ceramic Manufacturing Industry. August 2007. Available on https://eippcb.jrc.ec.europa.eu/sites/default/files/2019-11/cer_bref_0807.pdf
European Commission, 2013. On the implementation of the Raw Materials Initiative. COM(2013) 442 final report. Report from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions. Brussels. Available on https://www.europarl.europa.eu/RegData/docs_autres_institutions/commission_europeenne/com/2013/0442/COM_COM(2013)0442_EN.pdf
European Commission, 2020. Study on the EU’s list of Critical Raw Materials – Final Report. Directorate-General for Internal Market, Industry, Entrepreneurship and SMEs, Brussels. Available on https://ec.europa.eu/docsroom/documents/42883/attachments/1/translations/en/renditions/native
European Commission, n.d. Extractive waste. Mining. Waste streams. Waste. DG Environment. European Commission. Available on https://ec.europa.eu/environment/waste/mining/index.htm
Eurostat, n.d. Waste Generation 2016. Eurostat. Statistics Explained. Available on https://ec.europa.eu/eurostat/statistics-explained/index.php/Waste_statistics#Total_waste_generation
IRP, 2019. Global Resources Outlook 2019: Natural Resources for the Future We Want. Report of the International Resource Panel (IRP) from the United Nations Environment Programme (UNEP). Nairobi, Kenya. Available on https://www.resourcepanel.org/reports/global-resources-outlook
Lemougna, P.N., Yliniemi, J., Ismailov, A., Levanen, E., Tanskanen, P., Kinnunen, P., Roning, J., Illikainen, 2019. Recycling lithium mine tailings in the production of low temperature (700–900°C) ceramics: Effect of ladle slag and sodium compounds on the processing and final properties. Construction and Building Materials, Volume 221, pp. 332-344. DOI: https://doi.org/10.1016/j.conbuildmat.2019.06.078
Menezes, R.R., Almeida, R.R., Santana, L.N.L., Neves, G.A., Lira, H.L., Ferreira, H.C., 2007. Analysis of the use of kaolin processing waste and granite sawing waste together for the production of ceramic bricks and roof tiles. Cerâmica, Volume 53, pp. 192-199. DOI: https://doi.org/10.1590/S0366-69132007000200014
UN, 1997. Glossary of Environment Statistics. Studies in Methods, Series F, No. 67, United Nations, New York. Available on https://unstats.un.org/unsd/publication/SeriesF/SeriesF_67E.pdf
UNEP, 2011. Decoupling natural resource use and environmental impacts from economic growth, A Report of the Working Group on Decoupling to the International Resource Panel. Available on https://www.resourcepanel.org/reports/decoupling-natural-resource-use-and-environmental-impacts-economic-growth
Veiga Simão, F., Chambart, H., Vandemeulebroeke, L., Cappuyns, V., 2021. Incorporation of sulphidic mining waste material in ceramic roof tiles and blocks. Journal of Geochemical Exploration, 106741. DOI: https://doi.org/10.1016/j.gexplo.2021.106741
VLAREMA, 2012. Decree of the Flemish Government establishing the Flemish regulations concerning the sustainable management of material cycles and waste. Last modified on December the 7th 2019. Available on https://navigator.emis.vito.be/mijn-navigator?woId=43991&woLang=nl