Characterisation of excavated landfill waste fractions to evaluate the energy recovery potential using Py-GC/MS and ICP techniques

Abstract

Fuelled by further planet degradation concerns, the circular economy concept spreads worldwide, incorporating the need for the closing of material loops. This can be done not only by waste prevention and recycling but also by excavating old landfill sites. In line with this need, the Enhanced Landfill Mining concept was developed, which covers mining of old landfills combined with material and energy recovery from the excavated material. Site-specific investigations of excavated material are required because the way of excavated material utilisation has to be individually tailored to the material features. In this article, the valorisation options for the excavated waste from the old part of the landfill located in Mont-Saint-Guibert (Belgium) are preliminarily assessed. Seven separated waste fractions were analysed regarding their thermal decomposition pattern (TGA), pyrolysis potential (Py-GC/MS), and elemental composition (ICP-OES). Most of the analysed fractions are characterised by a highly heterogeneous composition, which excludes their primary or secondary recycling. The fractions are also characterised by high calorific value, which indicates the potential for thermochemical utilisation (i.e., pyrolysis). The presence of a significant amount of heavy metals (especially Hg and Pb) and chlorine may, however, pose a considerable risk of the contamination of pyrolysis products. It may require costly washing of the feedstock prior to the utilisation or cleaning of the process products prior to their use. Therefore, in order to limit additional costs, collective pyrolysis of all fractions seems to be a feasible way of their utilisation.