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Appraising the value of compositional information and its implications to scrap-based production of steel
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.ORCID iD: 0000-0002-4456-5949
KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability, Industrial Dynamics & Entrepreneurship.ORCID iD: 0000-0002-1185-3696
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.ORCID iD: 0000-0002-8802-4036
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.ORCID iD: 0000-0003-1919-9964
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2023 (English)In: Mineral Economics, ISSN 2191-2203, E-ISSN 2191-2211Article in journal (Refereed) Published
Abstract [en]

The current nature of steel design and production is a response to meet increasingly demanding applications but without much consideration of end-of-life scenarios. The scrap handling infrastructure, particularly the characterization and sorting, is unable to match the complexity of scrapped products. This is manifested in problems of intermixing and contamination in the scrap flows, especially for obsolete scrap. Also, the segmentation of scrap classes in standards with respect to chemical compositions is based on tolerance ranges. Thus, variation in scrap composition exists even within the same scrap type. This study applies the concept of expected value of perfect information (EPVI) to the context of steel recycling. More specifically, it sets out to examine the difference between having partial and full information on scrap composition by using a raw material optimization software. Three different scenarios with different constraints were used to appraise this difference in terms of production and excess costs. With access to perfect information, production costs decreased by 8–10%, and excess costs became negligible. Overall, comparing the respective results gave meaningful insights on the value of reestablishing the compositional information of scrap at the end of its use phase. Furthermore, the results provided relevant findings and contribute to the ongoing discussions on the seemingly disparate prioritization of economic and environmental incentives with respect to the recycling of steel.

Place, publisher, year, edition, pages
Springer Nature, 2023.
Keywords [en]
Steel recycling, Steel scrap, Value of information, Excess cost, EVPI
National Category
Metallurgy and Metallic Materials
Research subject
Metallurgical process science
Identifiers
URN: urn:nbn:se:kth:diva-322972DOI: 10.1007/s13563-022-00361-zISI: 000907055700002Scopus ID: 2-s2.0-85145554276OAI: oai:DiVA.org:kth-322972DiVA, id: diva2:1725111
Note

QC 20230116

Available from: 2023-01-10 Created: 2023-01-10 Last updated: 2024-03-15Bibliographically approved
In thesis
1. Recirculation of scrapped resources: The role of material information in enhancing the sustainability of recycling
Open this publication in new window or tab >>Recirculation of scrapped resources: The role of material information in enhancing the sustainability of recycling
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Industries have responded to the climate change problem by positioning their activities as compatible with concepts such as the Circular Economy. Conveying the idea of maximizing and keeping the resources in a manner that aligns with the principles of sustainable development, the endorsements for implementing circularity measures has arguably become a boon for businesses. Firms that have traditionally consumed both primary and anthropogenic resources in the production of materials used in infrastructure, transportation, and other technological requirements are in a special position. On the one hand, their products are needed for societal development. But on the other hand, their activities emit considerable amounts of greenhouse gases.

The steel industry is a classic example where material and energy resource savings are achieved when the End-of-Life (EoL) products are recycled. However, these assumed efficiencies are provisional to scrap being a suitable replacement for ore-based resources. The replacement of primary (i.e. purer) - with secondary (i.e. contaminated) as feedstock for production depends heavily on a recycling system’s capability to deal with the complexity of the ferrous scrap streams that society is generating. More specifically, in reference to recovering the material identity through characterization and sorting that lessens or avoids the current practice of either diluting contaminants or compensating for insufficient alloying through addition of primary resources.

This present thesis takes a critical look at the use of scrap with the view that recycling is a technical process that is carried out by enterprises. The impression that recycling consequently replaces the use of primary resources is scrutinized, with consideration of scrap as a characteristically appropriate, but innately challenging feedstock to use. Case studies focusing on the Swedish scrap-based production context revealed that the recycling system actors operate and transact on the basis ofscrap’s quality, which in turn was interpreted as being multidimensional and dependent on each actor’s preferences. The alignment of economic and environmental interests connected with scrap utilization was found to be limited, with companies preferring the use of primary resources when scrap is no longer suitable.

The idea of suitability was then ascribed to compositional information regarding scrap and tested at two levels: having access to partial or full information. The former is what is achieved through the current scrap handling in the reverse loop while the latter is an idealized situation where the exact chemistry of the scrap is known. An optimization program was then used to simulate steel recycling where the scenarios tested were designed to focus on the response of the production model to the scrap chemistry of the input materials. The results obtained showed an overall decrease in production costs and an increase in the proportion of scrap used in production. In most cases, this was attributed to the flexibility to allocate scrap based on its composition to the closest matching target products.

Finally, additional interviews with industry practitioners further clarified established, company-based protocols for dealing with the lack of information and provided insights with regard to opportunities for increasing scrap utilization. An analysis of the responses suggested that there are contextual differences when it comes to practices by each company, and even attitudes, towards anthropogenic resources. Ultimately, the insights from this thesis lend support to the need of enterprises to address the trade-offs related to scrap utilization and lead to enhanced sustainability in steel recycling.

Abstract [sv]

Industrier bemöter klimatkrisen genom att positionera verksamheten i linje med begrepp såsom cirkulär ekonomi. Genom att förmedla idén om att optimera och cirkulera resurser på ett sätt som överensstämmer med principerna för hållbar utveckling har trycket för att genomföra åtgärder för cirkularitet ökat, samtidigt som det finns tydliga ekonomiska incitament. Företag som traditionellt har förbrukat både primära och antropogena resurser i produktionen av material som används inominfrastruktur, transport och för andra tekniska behov har en särskild ställning. Å ena sidan behövs deras produkter för samhällsutvecklingen. Men å andra sidan ger deras verksamheter upphov till betydande mängder växthusgaser.

Stålindustrin är ett klassiskt exempel där besparingar av material- och energiresurser uppnås när produkterna återvinns i slutet av deras livscykel. De positiva effekterna är dock beroende av att skrotär en lämplig ersättning för malm-baserade resurser. Ersättningen av primära (dvs. renare) resurser med sekundära (dvs. förorenade) som råmaterial för produktionen är starkt beroende avåtervinningssystemets förmåga att hantera komplexiteten hos de järn- och stål-skrotströmmar som samhället genererar. Mer specifikt, behöver aktörerna i värdekedjan återställa materialets identitet genom karaktärisering och sortering som minskar eller undviker den nuvarande praxisen att antingen utspäda föroreningar eller kompensera för otillräcklig legering genom tillsats av primära resurser.

Denna avhandling granskar användningen av skrot med uppfattningen att återvinning är en tekniskprocess som utförs av företag. Intrycket att återvinning följaktligen ersätter användningen av primära resurser granskas, med beaktande av skrot som ett karaktäristiskt lämpligt men samtidigt utmanande råmaterial att använda. Fallstudier som fokuserar på den svenska skrotbaserade produktionskontexten visade att aktörerna inom återvinningssystemet agerar baserat på skrotets kvalitet, vilket i sin tur tolkades som mångdimensionellt och beroende av varje aktörs preferenser. Samstämmigheten mellan ekonomiska och miljömässiga intressen kopplade till skrotanvändning visade sig vara begränsad, med företag som föredrog användningen av primära resurser när skrot inte längre var lämpligt.

Tanken på lämplighet tillskrevs sedan kompositionell information om skrot och testades på tvånivåer: att ha tillgång till partiell eller fullständig information. Det förra är vad som uppnås genomden nuvarande hanteringen av skrot i den omvända loopen medan det senare är en idealiserad situation där den exakta kemin hos skrotet är känd. Ett optimeringsprogram användes sedan för att simulera stålåtervinning där de testade scenarierna var utformade för att fokusera på produktionsmodellens respons på skrotets kemiska sammansättning. De erhållna resultaten visade en övergripande minskning av produktionskostnaderna och en ökning av andelen skrot som används i produktionen. I de flesta fall tillskrevs detta flexibiliteten att tilldela skrot baserat på dess sammansättning till de närmast matchande målprodukterna.

Slutligen klargjorde ytterligare intervjuer med branschutövare etablerade och företagsbaserade protokoll för att hantera bristen på information och gav insikter med avseende på möjligheter att öka skrotanvändningen. En analys av svaren antydde att det finns kontextuella skillnader när det gäller praxis från varje företag, och även attityder, gentemot antropogena resurser. Slutligen stöder insikterna från denna avhandling behovet för företag att hantera de kompromisser som är relaterade till skrotanvändning och leder till förbättrad hållbarhet inom stålåtervinning.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2024. p. 77
Series
TRITA-ITM-AVL ; 2024:4
Keywords
Steel recycling, anthropogenic resources, scrap, value of information, Circular Economy, sustainability, Stål återvinning, antropogena resurser, skrot, cirkulär ekonomi, hållbarhet
National Category
Materials Engineering
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-343560 (URN)978-91-8040-856-1 (ISBN)
Public defence
2024-03-15, Kollegiesalen - https://kth-se.zoom.us/j/66736996132, Brinellvägen 8, Stockholm, 09:00 (English)
Opponent
Supervisors
Available from: 2024-02-21 Created: 2024-02-19 Last updated: 2024-03-12Bibliographically approved

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Compañero, Reinol JosefFeldmann, AndreasSamuelsson, PeterTilliander, AndersJönsson, PärGyllenram, Rutger

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