Environmental and Economic Performance of Enhanced Landfill Mining

Abstract

Enhanced Landfill Mining (ELFM) is an innovative concept developed to reintroduce historic waste streams present in the landfills to the material cycle either as energy or as materials. Besides, ELFM contributes to minimise the environmental and social impacts of landfills and to regain the large areas of land. The objective of this work was to investigate the environmental and economic performance of this ELFM concept. The research consisted of three parts. In the first part, the general process flow diagram and a model to assess the environmental and economic performances of ELFM were developed. Traditional landfill mining case studies were considered in order to decide the major components to be in the process flow diagram of ELFM. The model was based on life cycle assessment and life cycle costing tools. The model allowed the assessment of the overall impact of the entire ELFM system, individual processes, and also of the trade-off between environmental and economic performances. In the second part, the model was applied to the first ELFM case study to assess its environmental and economic feasibility. The study showed clear environmental benefits of ELFM against the landfill’s existing situation. The study revealed that the thermal treatment process is the most important process both environmentally and economically. A cluster of environmental and economic drivers (recovery efficiencies of refuse derived fuel and metals, net electrical efficiency and investment cost of thermal treatment process, calorific value of refuse derived fuel, and price of electricity) that should be cautiously controlled in future ELFM studies, were identified. A separate analysis was conducted to identify the impact of use of thermal treatment residues to produce building materials such as aggregates and alternatives for products based on Portland cement. The study revealed that the quality of the products determines the net environmental and economic impacts of valorisation routes of thermal treatment residues. In addition, the study showed that the higher value applications of thermal treatment residues (alternatives for products based on Portland cement) are necessary to acquire the higher environmental benefits and economic profits. Furthermore, a detailed analysis was performed to identify the impact of plasma gasification in the context of ELFM. The study concluded that plasma gasification is a viable candidate in ELFM due to its combined energy and material valorisation capacity, which shows an overall better environmental and economic performance than a conventional incineration process. The analysis further confirmed that the environmental and economic performance of plasma gasification can be improved by using thermal treatment residues to produce building materials instead of landfilling. In the last part, the ELFM concept was applied to reduce the environmental and socio-economic impacts due to open waste dumps in a developing country. It was found that the open waste dump mining largely eliminates the global warming potential caused by the emission from uncontrolled dumps. However, the study confirmed the need for the government’s involvement in order to achieve the economic profits of open waste dump mining in a developing country.