Abstract
The recycling of scrap is one of the common approaches aiming at reduction of mining-based production of critical metals and mitigation of their supply risk as well as processing-related environmental impact. The number of currently available end-of-life vehicles (ELVs) indicates—significant potential for critical metals recycling, especially niobium (Nb). Therefore, the quantification of environmental impact of niobium recovery starts to be an important issue in assessment of sustainability of large-scale recycling processes. In this paper, we assess energy consumption and greenhouse gas (GHG) emissions in individual stages of niobium supply chain in the automotive industry over the period 2010–2050. The different stages including mining, production and recycling are analyzed using dynamic simulation. The results show the majority of the consumed energy (45% of energy demand in niobium supply chain) is used in the primary production stage. This stage also contributes to 72% of total gas emissions of supply chain over the period 2010–2050. Mining of niobium consumes up to 36% of energy and generates ca. 21% of GHG emissions. While, in recycling stage, the secondary production of niobium requires 19% of supply chain energy and generates 7% of gas emissions. The detailed calculations show that recycling of niobium could save around 133–161 m GJ energy between 2010 and 2050. The recycling would also contribute to the reduction of 44–53 mt CO2-eq in the same period. It shows around 18% reduction of annual emissions between 2010 and 2050 thanks to reuse of niobium in secondary production rather than primary production.
Highlights
Niobium (Nb) is an essential element for production of steel and superalloys, superconductors, electronic components, medical implants, etc
The balance of energy consumption and greenhouse gas (GHG) emissions from the supply chain helps to determine the environmental sustainability of recycling and the level of investment in recycling
The correlation between energy consumption and GHG emissions is clearly visible in all stages of niobium supply chain
Summary
Niobium (Nb) is an essential element for production of steel and superalloys, superconductors, electronic components, medical implants, etc. It is worth to mention that the niobium demand has increased dramatically over the past decade, as an element of microalloys in high strength and stainless steels used in the automotive industry [6]. In 2010, based on the available global number of ELVs, the amount of niobium in high-strength steel (HSS) alloy used in passenger cars (average weight 1.5 tonnes) could be estimated at around 36,000 tonnes compared to 49,100 tonnes of niobium mined globally [15]. The question remains as to what levels of energy consumption and GHG emissions at each stage of the niobium supply chain would ensure environmental sustainability. The main objective of this paper is to present a dynamic model of the niobium supply chain to investigate energy consumption and GHG emissions at each stage including mining, production and recycling
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