Landfill mining: A case study regarding sampling, processing and characterization of excavated waste from an Austrian landfill

Abstract

The following case study belongs to the New-Mine project and the objective of the project is to develop a new “Enhanced Landfill Mining” (ELFM) scenario for a combined resource-recovery and remediation strategy. This strategy could reduce future remediation costs and reclaim valuable land while simultaneously unlocking valuable resources. In the past, insufficiently reliable data about the composition of landfills, overestimation of the quality of excavated material and poor product marketing of the possible recyclables have resulted in a bad reputation for landfill-mining projects. The ongoing research in the NEW-MINE project shall show that there are possibilities to create valuable outputs from landfills with enhanced treatment processes, such as a better distribution of the different mechanical processes. To create mechanical routes to recover valuable materials from old landfills, it is important to characterize the material, creating a basis for the research. The objective of this case study, executed from November 2016 until June 2017 at the landfill site in Halbenrain (Austria), is to study the efficiency of different sorting technologies with old landfill material. The excavated material was transported and used as feedstock in a configured state-of-the-art mechanical-biological treatment (MBT) plant located next to the landfill. During the mechanical processing, metals and high-calorific fractions were sorted out from the input flow. As a result of the mechanical processing, approx. 3% of the ferrous metals were recovered, approx. 20% of potential RDF (pRDF) was separated and could have been energetically recovered, and approx. 74% belonged to the finer fraction (< 40 mm). Each sample from the sampling campaign was sieved to obtain the particle size distribution. Via manual sorting, the material was classified into plastics, wood, paper, textile, inerts, Fe metal, NF metals, glass/ceramic and residuals. In addition, the moisture (wt%), the ash content (wt%), the calorific value (MJ/kg) and the concentration of heavy metals (%) of the finer fraction (<40 mm) were analysed. The aim of this study is to assess the possibilities of different mechanical processes with landfill mining (LFM) material and to gain information about the characterization of five material flows derived from the mechanical treatment, together with the mass balance of the MBT. Although every landfill has its own characteristics, the results obtained from this case study can help to understand the general potential, contribute to develop methodologies for characterization of old landfill material and identify problematic fields that require further research.