Life Cycle Comparison of Battery Recycling and Conventional Material Refining

Abstract

Background: The rise of renewable energy generation and vehicle electrification has created exponential growth in lithium-ion battery (LIB) production, particularly for electric vehicles.1 However, the limited supply of raw materials needed for prominent battery chemistries has exacerbated concerns linked to economic, environmental, national security, and human rights dimensions.2 For example, raw materials necessary for LIB production are not equally distributed, and current supply chains are insufficient for projected demand. For countries with natural reserves of critical LIB elements, the mining of ore for battery production often involves the destruction of natural ecosystems and sometimes employs child labor under harsh working conditions.3 Further, many small LIBs in consumer electronics are carelessly disposed of in garbage or recycling bins at end-of-life. Because these disposal streams are not designed to process energized batteries, LIBs have caused fires and millions of dollars in damage to waste management and recycling centers.4 Taken together, these concerns underscore the need for robust recycling programs for LIBs and their components. Methods: We performed a comparative environmental assessment of the gate-to-gate refinement process of battery material production based on conventional battery material refining versus LIB recycling by Redwood Materials. Two- and three-step recycling processes were assessed for battery feedstocks that included production scrap and mixed spent lithium-ion batteries. Data detailing energy, water, and consumables usage were provided by Redwood and normalized to elemental mass flows and products of interest. The system boundary does not include other operations at Redwood Materials outside of the direct refinement processes nor the embodied resources in the capital equipment used for material refinement.The functional unit employed in the analysis was a 1 kg of active nickel, cobalt, aluminum oxide (NCA) battery material. The primary LCA criteria evaluated included global warming potential (CO2eq), primary energy demand, and water consumption. Data for conventional material refining were adapted from the Argonne National Laboratory’s Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET®) 2020 model. GREET was also employed to acquire the life cycle parameters for producing consumables used in both conventional metal refining and Redwood Materials’ recycling processes to provide common scaling factors. Transportation between stages was not included in this analysis because it was not consistently available in the GREET model. The environmental metrics for each metal pathway were normalized by the mass of the individual element of interest within the final product and then normalized again by the mass of that element in the functional unit. Results and Implications: The goal of this study was to compare environmental metrics of two scenarios: (1) conventional refining of raw battery materials and (2) recycling of batteries by Redwood Materials. Relative to conventional refining, the Redwood Materials recycling processes reduced both water (by 70–80%) and energy consumption (by 81–87%) per kg of NCA battery active material. The Redwood processes lowered CO2 emissions by 67–68% compared to conventional ore refining. The output products of each recycling process were dependent on the battery feedstock and recycling efficiency. In the case of Ni-rich feedstock, the CO2 emissions by mass of Ni were 30–45 times lower for recycling versus conventional refining when considering only nickel as the output product.In addition to comparing recycling processes to conventional refining, we also conducted a prospective life-cycle assessment to identify optimization opportunities at Redwood. Among the three process steps (mechanical processing, low-temperature calcination, and hydrometallurgy), the hydrometallurgical process was the most resource- and carbon-intensive, counter to popular opinion. This was due to the embodied resources required to produce the input consumables Ca(OH)2, H2O2, and electricity from the Nevada electrical grid. The addition of a low-temperature calcination step prior to hydrometallurgy slightly reduced overall resource consumptions and emissions because fewer input consumables were needed for the hydrometallurgical step. Overall, this study identified value propositions and optimization opportunities for battery recycling as it reaches a much-needed scale to support the burgeoning LIB market. This assessment will guide battery recyclers on environmental targets, and inform several stakeholders (e.g., public, policymakers, electrochemists and electrochemical engineers) regarding the tradeoffs and opportunities for a circular battery economy relative to conventional battery manufacturing. References Electric Vehicles are starting to buoy the global metals market. https://www.bloombergquint.com/technology/the-relentless-march-toward-an-ev-future-is-good-news-for-miners.National Blueprint for Lithium Batteries; U. S. Department of Energy: 2021.Findings on the Worst Forms of Child Labor: Democratic Republic of the Congo. https://www.dol.gov/agencies/ilab/resources/reports/child-labor/congo-democratic-republic-drc.Staub, C. MRF operator: Lithium-ion batteries are ‘ticking time bombs’. https://resource-recycling.com/recycling/2021/04/13/mrf-operator-lithium-ion-batteries-are-ticking-time-bomb.