Evaluating energy and resource efficiency for recovery of metallurgical residues using environmental and economic analysis

Abstract

Energy and resource efficiency are today key elements for the metallurgical industry in the context of the new European Green Deal. Although the currently available technologies have recently led to an optimisation of energy and materials use, the decarbonisation targets may not be met without the development of new and innovative technologies and strategies. In this context, the goal of the H2020 project CIRMET (Innovative and efficient solution, based on modular, versatile, and smart process units for energy and resource flexibility in highly energy-intensive processes) is to develop and validate an innovative and flexible circular solution for energy and resource efficiency in a metallurgical plant. The circular model proposed is composed of three units: (1) a metallurgical furnace for the recovery of valuable metals from industrial metallic wastes, (2) a unit for heat recovery from the furnace’s exhaust gases, and (3) a digital platform for the optimisation of the whole process. Also, the circular model investigates the possibilities of substituting the metallurgical coke used in the furnace with biobased material (BIOCHAR). This study presents an environmental and economic assessment of the circular model, based on a real pilot testing campaign in which residues from non-ferrous metals production are treated for the recovery of metals, mechanical energy from waste heat, and inert fraction. Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) are used to assess the environmental and economic performances of the circular model. The results of the LCA and the LCC highlight the main environmental and economic hot spots of the proposed technologies. The environmental analysis showed the environmental positive effects of recovering secondary metals and energy. However, for some environmental impact categories (e.g. climate change), the benefits are balanced out by the high electricity and natural gas demand in the metallurgical furnace. In this regard, the substitution of metallurgical coke with BIOCHAR can significantly lower the environmental impacts of the whole process. The economic analysis showed the potential economic profitability of the whole process, depending mostly on the quantity and marketability of the recovered metals. For both environmental and economic analysis, the electricity demand in the metallurgical furnace represents the main barrier that can hinder the viability of the process. Therefore, looking for alternative energy sources (e.g. waste heat from other industries) is identified as the most effective strategy to push the sustainability of the whole process. As the proposed technology is under development, these preliminary results can provide useful insights and contribute to the environmental and economic optimisation of the technology.