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Posted: Jan 27, 2015
Nanowaste - Nanomaterial-containing products at the end of their life cycle (page 4 of 4)
Behavior of nanomaterials in waste incineration plants
Little information is currently available about how nanomaterials behave in waste incineration plants or in landfills. Studies have been conducted on only a few materials, for example on ceroxide nanoparticles that were experimentally introduced into an incineration plant. The results show that these were neither chemically nor physically altered by the incineration process, but that they were effectively retained in the facility’s filters.
Nanoparticles that bond with the solids in the facility, however, ultimately end up with the combustion residues in landfills. Thus, the disposal problem in the case of stable ENMs is merely shifted to the subsequent steps in the waste treatment process.33
Studies in Switzerland show that only a tiny fraction (on average ca. 0.00079 percent by weight) of the filter dust of incineration plants is present in the form of nanoparticles and that these make up less than 10% of the total particle counts. Model calculations revealed that most of the nanoparticles (nanosilver, TiO2, ZnO) in the wastes (residual wastes, wood, sludge) are present in form of bottom ash34 and end up in landfills. In contrast, CNTs are almost completely combusted (94%)35.
The behavior of nanomaterials in waste incineration plants can currently be summarized as follows:36,37
When incinerated, nanomaterials can either be destroyed, converted into other nanomaterials (e.g. oxides, chlorides) or be released unchanged.
Nanomaterials in the size class 100 nm and larger are most efficiently removed in the filters of waste gas purification systems.
Nanomaterials smaller than 100 nm are only partially retained by filters. An estimated up to 20% can be released.
Incinerating nanomaterials can accelerate the formation or destruction of undesired by-products (e.g. polycyclic aromatic hydrocarbons).
Nanomaterials can be retained in the solid wastes (ash, slag, filter residues) produced by waste incineration plants. A leach ing of nanomaterials from such wastes, for example when subsequently dumped in a landfill, should be avoided (landfill base sealing, leachate treatment, surface sealing etc.).
Various nanomaterials are currently being incorporated in a wide range of products. It remains largely unknown whether these can pose an environmental or health risk when they end up in waste treatment plants or in landfills via various waste streams at the end of their life cycle. In a precautionary approach, several experts and organizations have therefore formulated first recommendations designed to minimize nanomaterials in wastes. Future research efforts should increasingly focus on the disposal phase of „nanoproducts” in order to better estimate potential risks.
5 Wiechmann, B., Dubbert, W., 2011, Umweltaspekte von Nanoabfällen, Informationsdienst für die Abfallwirtschaft in Brandenburg und Berlin, Sonderabfallgesellschaft Brandenburg/Berlin mbH, forum IV-2011.
6 Boldrin, A., et al., 2014, Environmental exposure assessment framework for nanoparticles in solid waste. Journal of Nanoparticle Research 16, 1-19.
7 See Boldrin et al. (EN 6), page 4.
8 Mudgal, S. et al., 2011, Study on coherence of waste legislation. Final Report. European Commission (DG ENV). 11 August 2011.
9 Bestandsaufnahme der Abfallwirtschaft in Österreich. Statusbericht 2012. Umweltbundesamt, Wien, im Auftrag des BMLFUW, page 7.
10 Tellenbach-Sommer, M., 2010, Entwurf Konzeptpapier, Umweltverträgliche und sichere Entsorgung von Abfällen aus Herstellung sowie industrieller und gewerblicher Verarbeitung von synthetischen Nanomaterialien, Arbeitsgruppe "Entsorgung von Nanoabfällen", Commissioned by: BAFU.
11 Directive 2008/98/EG of 19 November 2008 on wastes and the repealing of certain directives.
17 The Project on Emerging Nanotechnologies, Woodrow Wilson International Center for Scholars, Consumer Products Inventory.
18 NanoTrust Dossier Nr. 009.
19 Table from: Möller, M. et al., 2013, Nanomaterialien: Auswirkungen auf Umwelt und Gesundheit, page 53, TA-Swiss 60/2013: Zentrum für Technikfolgen-Abschätzung, vdf Hochschulverlag AG an der ETH-Zürich.
20 NanoTrust Dossier Nr. 015en.
21 NanoTrust Dossier Nr. 010en.
22 See Möller et al. (EN 19), page 178.
23 NanoTrust Dossiers Nr. 008en and Nr. 033en.
24 NanoTrust Dossiers Nr. 027en.
25 NanoTrust Dossier Nr. 020en.
26 See Möller et al. (EN 19), page 179.
27 NanoTrust Dossier Nr. 032en.
28 See Möller et al. (EN 19), page 182.
29 NanoTrust Dossier Nr. 022en.
30 NanoTrust Dossier Nr. 024en.
31 Lozano, P. et al, 2012, Single-walled carbon nanotube behavior in representative mature leachate. Waste Management 32: 1699-1711.
33 Walser, T. et al., 2012, Persistence of engineered nanoparticles in a municipal solid-waste incineration plant, Nature Nanotechnology Letters, Vol. 7, 520-524.
34 Bottom ash refers to ash that accumulates in the combustion part (the bottom or grate) of the incineration facility.
35 Müller, N.C., et al., 2012, Nanomaterials in waste incineration and landfills, EMPA.
36 Roes, L. et al., 2012, Preliminary evaluation of risks related to waste incineration of polymer nanocomposites, Science of the Total Environment 417-428, 76-86.
37 Vejerano, E. P. et al., 2013: Emissions of Polycyclic Aromatic Hydrocarbons, Polychlorinated Dibenzo-p-Dioxins, and Dibenzofurans from Incineration of Nanomaterials. Environmental Science & Technology 47: 4866-4874.
By NanoTrust, Austrian Academy of Sciences. NanoTrust Dossiers are published irregularly and contain the research results of the Institute of Technology Assessment in the framework of its research project NanoTrust. The Dossiers are made available to the public exclusively on epub.oeaw.ac.at/ita/nanotrust-dossiers.