Advancing Circular Economy through Phytomining: Critical Mineral Recovery from Mine Tailings and Environmental Impact Assessment

In addition to exploring global hyperaccumulators for extracting U.S. Geological Survey (USGS)-listed Critical Raw Minerals (CRMs) from mining waste, a life cycle assessment (LCA) was done to evaluate the environmental profile of phytomining. The functional unit was 1 kg of each type of CRM produced, considering different steps from farming to metal extraction based on three different scenarios of low bioaccumulation (LB), medium bioaccumulation (MB), and high bioaccumulation (HB). It was found that organic reagents, such as ethylenediaminetetraacetic acid (EDTA) and citric acid, had higher environmental impacts compared with inorganic ones during the farming step. Furthermore, the LB scenario generated higher environmental impacts due to increased material and energy usage. The main finding was that the CO2 emissions from LB, MB, and HB were 42.97, 30.23, and 22.03 kg CO2 equiv, respectively. Considering the photosynthesis process, the actual carbon footprints were −58.67, −52.61, and −46.99 kg of CO2, respectively. This paper presents not only the first local database for hyperaccumulators for CRM phytomining, along with comprehensive guidelines for ecological restoration and succession, leading to advanced phytomining, but also the first LCA of this new process based on different bioaccumulation scenarios of metals.