Abstract
The UN Sustainable Development Goal 12, regarding responsible production and consumption of raw materials, guides ongoing international efforts to enhance sustainability in all parts of the mineral sector. Of particular interest, is improving the recyclability of secondary waste streams and thereby increasing the efficiency of recycling end-of-life products. Municipal solid waste – residual waste from household and industry – constitutes one of these secondary streams. It is typically incinerated in waste-to-energy plants producing two types of waste streams that carry a raw material resource potential: incinerator bottom ash (IBA) and incinerator fly ash (IFA). IBA is of particular interest in the recycling industry, where it is commonly recycled to produce three main fractions: (i) ferrous material, (ii) non-ferrous material, and (iii) residual slag. In most cases the two metal fractions are separated further downstream in the value chain, prior to smelting. The residual, non-magnetic fraction (typically 0–45 mm) is used mainly as construction aggregate. Improvements in the efficiency of existing separation technologies are still being made, but less effort is focussed on characterising the fundamental composition and mineral resource potential of IBA. For this reason, the Urban-X project was launched by the Geological Survey of Denmark and Greenland (GEUS) to characterise the composition and resource potential of various waste streams at Amager Bakke waste-to-energy plant in Copenhagen, Denmark. This paper discusses some of the main outcomes of the Urban-X project with respect to IBA, and a full analysis of all waste streams analysed at Amager Bakke is available in Clausen et al. 2019.
Highlights
Four incinerator bottom ash (IBA) samples were collected in duplicate from Amager Bakke plant each day for 30 consecutive days in November 2017
Five material classes dominated the coarse fraction of the IBA-bulk sample: magnetic metal (29 wt%), non-magnetic metal (6 wt%), glass (14 wt%), ceramics and building aggregates (14 wt%) and melt (37 wt%; Figs 1B, C)
The composite IBA-bulk sample consisted of 66 wt% coarse (2–63 mm) material and 34 wt% fine (< 2 mm) material
Summary
Four IBA samples were collected in duplicate from Amager Bakke plant each day for 30 consecutive days in November 2017 (series A–D, Fig. 2). We combined one series into a composite sample, which represented the average IBA material collected during the 30 days of sampling (C series, Fig 2). Additional subdivisions were made according to the degree of degradation; glass for example was subdivided into four sub-classes This part of the study is not reported in this article but can be found in Clausen et al 2019. A classical mineral exploration approach would be to produce an IBA ‘whole-rock’ chemical signature to identify potentially economic elements and minerals. This is neither possible nor meaningful for IBA material for the following reasons: 1. This is neither possible nor meaningful for IBA material for the following reasons: 1. The technical challenge: Homogenisation by means of crushing and milling of IBA material is expensive, if not impossible, due to the content of ductile metal fragments
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