Landfill Mining: Prospecting metal in Gärstad landfill

Abstract: All processes in society produce waste. In nature, the waste is normally used as a resource for another process, but in human societies waste is often discarded. These discarded materials end up in places for depositing waste known as landfills. The increase in population, and humans’ tendency to improve their quality of life, has led to an increase in consumption of material. More material consumption means generating more waste, and more waste means bigger landfills. The increasing size of landfills has brought some other issues, such as increased land use and higher environmental impact. However in these landfills a lot of valuable materials are discarded and the concept of landfill mining (LFM) has been proposed in order to solve these issues and use landfills as a possible source of materials. Landfill mining is not yet a common practice, and the first barrier for this is the uncertainty of the amount and value of materials within landfills. The purpose of this study is to prospect the amount of metals in one specific landfill, in this case Gärstad landfill in Linköping, Sweden.  This is a first step to show the feasibility of landfill mining as an alternative way of extracting materials. The study is limited only to metals because they are one of the most important resources in today’s society. The theoretical background of the study is based on material flow analysis (MFA). Two approaches are used to study the materials in the landfill. The first is top-down which studies the flows of materials and the second is bottom-up which studies the stocks of material in the landfill. Based on these approaches the method was developed. First the system boundaries in time and space were defined. Then the amount of waste in landfill was estimated from the two mentioned approaches. In the end the metal content of the waste was estimated. Some criteria are also defined to compare the accessibility of the metals in the landfill. The results of this study show that there is a considerable amount of metals in the landfill, and that ash deposits resulting from incineration are the most interesting source of metals; with iron, aluminium, copper and zinc being the most abundant. The results are presented by type of waste, area of the landfill and accessibility in order to identify the hotspots. Later it is discussed that the method is cheap and fast but highly depends on previous data and available information. Also the metal content of the landfill is compared with natural ores. In the end the metal content of the landfill is evaluated and estimated to be around 3 billion SEK. It shows that aluminium, titanium and copper have the highest value money wise. As conclusion it was shown material flow analysis is a valid way to prospect landfills. But further cost-benefit analysis must be carried out to determine if landfill mining is justifiable. Also some recommendations are proposed to Tekniska Verken in order to facilitate future studies. The first is to develop a systematic way for landfilling different kind of waste and document them. Second is to include metals which have economic potential in the regular sampling from landfill.