Date of Award

2016

Degree Type

Thesis

Degree Name

Master of Science in Systems Engineering

Department

Mechanical, Industrial and Systems Engineering

First Advisor

Gretchen A. Macht

Abstract

Over three hundred thousand battery electric vehicles (BEV) and plug-in hybrid electric vehicles (PHEV) are currently registered in the United States (US) as of 2015, which is less than one percent of the total vehicle market share. An expected increase for electric vehicles (EV), half of all vehicles sold in the US are expected to be EVs by 2020, will inevitably lead to a high number of EV batteries reaching their end-of-life (EOL). Manufacturers must create processes to ensure a sustainable management system in order to fulfill government recycling regulations while assuming environmentally friendly processes. Recycling used EV batteries presents unique economical and ecological challenges, considering the increased volume, diversity of car batteries, and the lack of a generalizable disposal processes. Specifically, the sustainability aspect of recycling processes for EV batteries currently lacks assessment, in order to establish a more environmentally friendly and economically efficient process for battery recyclers.

Sustainability’s “triple bottom line” is based on three factors: humans, the economy, and the environment. This study investigates the different recycling processes for EV lithium-ion batteries (LIB) and the associated environmental impacts and economical aspects based on the potential increased use. In order to generate the data required for an Input-Process-Output (I-P-O) model of the different processes, companies who recycle LIBs were identified. An environmental assessment of the recycling processes was performed using Life Cycle Assessment (LCA) executed via Umberto NXT LCA. The LCA explores the comparability of the disposal processes for LIBs and quantifies the process value regarding the ecological impact with regards to the Global Warming Potential (GWP), the Human Toxicity Potential (HTP), and the Terrestrial Ecotoxicity Potential (TETP). The generated results highlighted, that a major part of the environmental impacts of the recycling processes are related to the landfill of material waste, the incineration of plastics and the generated electricity, especially for energy intensive processes, such as smelting treatment methods. In terms of environmental effects, this paper identified processes that utilize low temperatures and recover both plastics and lithium as the most beneficial processes.

To contrast the economical perspective of the different industrialized recycling processes a comparison matrix was created. The most commonly recovered materials with one of the highest values per metric ton of spent LIBs are copper, nickel, and cobalt. After determining the benefit of the different recycling processes, by evaluating the system inputs and outputs, the processes were rated on an economical level, depending on the amount of benefit generated. Overall, the recycling processes, involving different combinations of mechanical-, hydro-, and pyrometallurgical treatment steps, from five companies were compared. This paper suggests utilizing recycling processes based on a combination of mechanical and hydrometallurgical or mechanical-, pyro- and hydrometallurgical process steps, contrasting both, environmental and economic aspects. Pure pyrometallurgical treatment methods or a combination of mechanical and pyrometallurgical processes are not suggested, especially due to the absence of a lithium carbonate recovery and a resulting deposit of lithium in the slag, or a lower lithium product output.

This research is one of the few studies in this area of EV LIBs and aims to further research, by identifying environmentally friendly and economically processes for battery recyclers. The presented results can be relevant to policy makers and recyclers since this type of waste is currently part of the European waste legislation for the treatment of Waste Electrical and Electronic Equipment (WEEE). The knowledge gained from this study will advise the recycling companies to be more conscious in their environmental behavior.

Further research can be established from this paper to assess how future LIB recycling could be examined in order to minimize the environmental impacts of recycling and how to improve the recovery of different materials. New recycling processes should be designed with a stronger orientation towards a more lithium based recovery in order to counteract a future lithium shortage.

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