Grain-Size Specific Characterisation and Resource Potentials of Municipal Solid Waste Incineration (MSWI) Bottom Ash: A German Case Study

Iveta Vateva,David Laner

doi:10.3390/resources9060066

Abstract

Municipal solid waste incineration (MSWI) is a major element of modern waste management and produces annually around 5.7 million tonnes of bottom ash (BA) in Germany. In order to save natural resources and protect the environment, utilisable materials need to be recovered from BA. It was the aim of the present study to determine metal and mineral resource potentials of MSWI BA based on a characterisation study of raw and aged BA of the MSWI plant in Kassel (Germany). The BA investigated consisted of 82.2% mineral materials, 16.3% metals, and 1.5% unburnt organic matter. Overall, 12.1% and 3.6% of the MSWI BA were theoretically recoverable as native ferrous (Fe) and non-ferrous (NFe) metals, respectively. Assuming state-of-the-art recovery technology, 10.7% and 2.0% of the BA were actually extractable as Fe and NFe metals. The processed BA, as a mixture, did not comply with current German limit values for use as a construction material mainly due to excessive soluble salt contents. Coarser grain size fractions were less contaminated, resulting in a utilisable potential of less than 30% of the BA as a construction material. Hence, grain-size specific processing routes need to be developed for MSWI BA to fully exploit its mineral resource potential.

Highlights

Municipal solid waste incineration (MSWI) is an important treatment method for non-recyclable waste in Europe
The partly significant differences, expressed as the standard deviation, in the nine daily samples regarding the material composition (Figure 5 and Table S5 of the Supplementary Information (SI)) indicate that MSWI bottom ash (BA) composition is subject to substantial daily variations
The aged BA consisted of 40.6% mineral fraction, 16.5% magnetic ash, 14.1% ferrous metals, 2.2% non-ferrous metals, 5.0% glass, 1.6% unburned

Summary

Introduction

Municipal solid waste incineration (MSWI) is an important treatment method for non-recyclable waste in Europe. Solid residues like bottom ash (BA) and fly ash remain. MSWI BA is the main solid residue and amounts to. MSWI plants operate wet BA discharge systems [4]. Wet discharged BA is characterised by the formation of new mineral phases and hardening processes. Potentially recoverable metals are bound in the mineral matrix [5]. MSWI BA is commonly processed in order to recover the metals contained. Due to its high water content, wet bottom ash must be stored (aged) prior to dry treatment. In Germany, the BA is currently stored for four weeks on average before processing, with a trend towards shorter aging periods [6]. Shorter aging facilitates the recovery of fine metals, which could otherwise be incorporated

Methods

Discussion

Conclusion