Municipal waste incineration fly ashes: from a multi-element approach to market potential evaluation

Anne-Lena Fabricius,Monika Renner,Roberta Graf,Anton Perfoll,Stephan Fromm,Michael Funk,Marieke Voss,Lars Duester,Florian Gehring

doi:10.1186/s12302-020-00365-y

Abstract

BackgroundFly ashes from municipal solid waste incineration contain significant amounts of (technology critical) elements. Processes to recover Cu or Zn are already in practice, but it still remains difficult to evaluate the full secondary resource potential of the ashes. One reason is the absence of a worldwide comparable analytical basis for detailed market analyses. To encounter this, (i) an advice on how to analyse 65 elements after microwave-assisted digestion by ICP-OES and ICP-MS is delivered, (ii) the heterogeneity (hours to annual cycle) is evaluated for a incineration plant, (iii) leaching efficiency with three different eluents and (iv) the market potential of the elements as commodities are evaluated.Results and conclusionsAqua regia digestion was found to be sufficient to evaluated the recovery potential; except for the mass constituents Al, Si, Sn, Ti and the trace components Cr, Hf, Nb, U and W, for which HF-containing digestions delivered better recoveries. On different time scales, ashes were very homogenous and HCl- as well as H2SO4-supported leaching delivered, satisfying results within an hour (exceptions are, e.g., Bi and Sb). By applying characterisation factors of the life cycle assessment impact category “Resource depletion—minerals and metals” supplemented by the list of critical raw materials of the EU: Ag, Bi, Cd, Ga, In and Sb are most interesting elements to be recovered in future activities.

Highlights

Fly ashes from municipal solid waste incineration contain significant amounts of elements
With respect to the analyses, the change of water content over a time period of ~ 1.5 years seems negligible, but should be considered if samples are stored for longer time periods
Particle size distributions of the intern reference material (IRM) showed a mean value of 39 ± 2 μm (Additional file 1: S2.2)

Summary

Introduction

Fly ashes from municipal solid waste incineration contain significant amounts of (technology critical) elements. An increasing number of investigations identified the different residues as potential secondary resources and addressed the challenges to recover metals from different matrices [12,13,14,15,16,17,18,19,20,21]. In this context it was accepted at an early stage, that speciation and fractionation of analytes are key factors with respect to leaching and were already addressed in the 1980s (e.g., [22, 23]). Comprehensive analyses combining a huge variety of compounds, time-dependent fluctuations, leaching characteristics and marked potential are still missing

Methods

Results

Conclusion