Heavy metals in soil-like material from landfills – Resource or contaminants?

Abstract

In the last decade landfill mining (LFM) has gained particular attention due to the possibility of resource recovery from landfills. However, landfills consist mainly of soil-like material (SLM) which is of little or no economic value. The aim of the present study is to provide a global overview of SLM in terms of heavy metal concentrations and its resource potential. As references for the resource assessment served metal concentrations in ores, thresholds for compost and earthworks, and abundance in Earth's crust. The preparation of a meta-analysis included 573 chemical analyses from 59 landfills in 12 countries. Average concentrations of arsenic, zinc and nickel turned out to be quite similar worldwide, whereas those of lead, copper and mercury showed remarkable differences between the landfills. Chromium, nickel, lead and zinc concentrations proved to exceed most likely compost, while arsenic and mercury concentrations remained usually below thresholds. With regard to a reuse of SLM in earthworks, elevated zinc concentrations were most of concern, followed by lead, copper, chromium and cadmium. However, chromium and nickel concentrations were found to be most similar to abundances in Earth's crust. Heavy metal concentrations in SLM were worldwide not comparable to those found in ores. Moreover, we observed that the option of multiple metal recovery did not improve significantly the resource potential.