Abstract

Metals recycling is one of the oldest industries in the United States that now employs over 530,000 individuals. It has always played a significant role in the economy, contributing $109.78 billion to the US economy in 2018. Furthermore, recycling supplies extensive goods and services, the Institute of Scrap Recycling Industries (ISRI) reported that every year greater than 900M Mt of scrap (~2 billion pounds) are consumed by manufactures globally, equating to 40% of the raw material demand. Additionally, as climate change becomes a greater threat, we must seek practices to lessen our carbon footprint, and recycling helps to reduce the environmental impact of metal production. Relying on this industry as an alternative to make-take-waste habits means understanding how the industry’s efficiency is being challenged by growing feed volumes of diverse, complex product designs. This work details the internal and external factors that impact the development of ferrous and nonferrous recycling operations. This knowledge is then applied to design and perform an extensive “true to yard” analysis with technologies that have potential for addressing inbound inspection and material identification challenges. These results allowed us to understand the limitations that would arise when attempting their deployment at material handling facilities, and then use these factors to build a model capable of quantifying and comparing these techniques, which is not available in previous literature. Inbound inspection and material identification are critical; they are the first opportunity once material is received to prevent comingling, downcycling, and contamination. Scrap yards identify and sort specific alloys from large quantities of mixed metals by means of visual and cognitive recognition with the aid of a few standard tools (a magnet, file, acids, and/or grinding wheel). This work tested handheld analyzers (HHs) that utilize x-ray fluorescence (XRF) and laser induced breakdown spectroscopy (LIBS) technology to determine the level of technological assistance they can provide to improving identification during the inspection process. Beforehand, we had a good indication of how HHs perform on material that has clean, smooth, uncoated surfaces (prompt scrap) but, what we aim to find is their response when used on “unprepared materials,” like those coming out of stock that are old, used, weathered, and/or warped (obsolete scrap). For these instruments to be deemed useful for inbound inspection/ identification purposes, it is crucial to understand and evaluate their limitations on scrap that is not altered and thus, true to a yard setting. Results indicate that in their current state, HHs can inform and verify content for a significant range of materials. They also show grade matching (identification of an alloy by name) is possible but less likely on unprepared scrap. However, the ability to register and share elemental composition percentages at rapid speeds, allows a trained user to know immediately what contaminants are present, often being high levels of Si and Fe. In addition to understanding how these technologies perform under real world conditions, it is also important to quantify whether their benefits outweigh their costs. This work examined five different scenarios for sorting and identification, each scenario offering different levels of alloy-specific sorting capabilities. The model that was created allowed for return on investment (ROI) comparisons, and evaluated the impacts of different market conditions, changes in volume, volume distribution, and uncertainty. This technoeconomic assessment showed that even a high amount of comingled material can be profitable at high volumes under certain market conditions. Although, comingling led to diminished profits, where segregating proved beneficial even at lower volumes. As we continue to invest, educate, and execute sustainable practices, we must understand that recycling should only come as an attempt after we have exhausted our efforts to reduce and reuse. Moreover, we can work to obtain a better balance along the supply chain by encouraging and creating more practices like design for recycling (DfR) and extended producer responsibility. Being that these behaviors will require a lot of societal reform, we need to ensure that we work to reduce landfill feed by providing the recycling industry with the tools and practices that are effective and efficient at getting materials identified and sorted.

Library of Congress Subject Headings

Scrap metals--Recycling--Technological innovations--Evaluation; Iron alloys--Identification; Sorting devices

Publication Date

8-13-2021

Document Type

Dissertation

Student Type

Graduate

Degree Name

Sustainability (Ph.D.)

Department, Program, or Center

Sustainability (GIS)

Advisor

Thomas Trabold

Advisor/Committee Member

Sandra Rothenberg

Advisor/Committee Member

Gabrielle Gaustad

Campus

RIT – Main Campus

Plan Codes

SUST-PHD

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