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Modelling for a sustainable coal-based direct reduction iron production using an integrated approach of circular economy and systems thinking for compliance and comprehensiveness and for eco-friendly environmental decision-making
Thesis (PhD (Industrial Engineering))--University of Pretoria, 2025.
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University of Pretoria
2026
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| access_status_str | Open Access |
| author2 | Ayomoh, Michael |
| author_browse | Ayomoh, Michael |
| author_facet | Ayomoh, Michael |
| collection | Thesis |
| dc_rights_str_mv | © 2024 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Thesis (PhD (Industrial Engineering))--University of Pretoria, 2025. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/108417 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-07-01T04:05:54.014Z |
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| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/108417 Modelling for a sustainable coal-based direct reduction iron production using an integrated approach of circular economy and systems thinking for compliance and comprehensiveness and for eco-friendly environmental decision-making Ayomoh, Michael u21837440@tuks.co.za Ncube, Ratidzo Yvonne UCTD Sustainable Development Goals (SDGs) Circular economy Direct reduction iron System dynamics Sustainability Thesis (PhD (Industrial Engineering))--University of Pretoria, 2025. The global shift towards sustainable industrial practices has intensified the need for environmentally responsible approaches to metallurgical processes, particularly coal-based Direct Reduction Iron (DRI). This study presents a holistic framework integrating the Hybrid Structural Interaction Matrix (HSIM), Circular Economy (CE) strategies, and System Dynamics (SD) to enhance the sustainability of coal-based DRI operations. This study identifies key waste drivers, maps their interactions, and quantifies the effects of 5R (Reduce, Reuse, Recycle, Recover, and Reclaim) CE interventions across multiple material and energy pathways. DRI metal is a preferred raw material to scrap metal in steel production; however, its production process is associated with substantial environmental burdens due to pollutants and waste generated. This research seeks to address the waste challenges and resource inefficiencies associated with the coal-based DRI process. Initially, HSIM was employed to prioritise and quantify material and energy flows within the DRI system, facilitating the identification of key waste streams. The Intensity Rating Factor (IRF) of the waste elements, computed from the HSIM, reveals that emissions and waste heat exhibited the highest weight intensity rating of 5.667, underscoring their substantial influence within the system. Subsequently, the prioritised streams are then aligned with the 5R framework (Reduce, Reuse, Recycle, Recover, and Reclaim) to develop targeted strategies for material circulation, thereby minimising losses and maximising resource efficiency. The Systems Thinking (ST) approach is utilised to generate a causal loop diagram, illustrating how waste from one stage of the process can be reused as input at another stage, thereby promoting material circularity. The developed 5R framework is then integrated into the DRI process to enhance resource efficiency, promote material recirculation, and minimise waste. A Circularity Index (CI) is derived as a metric to quantify the CE framework model for the coal-based DRI process. Case study data were utilised to illustrate the circularity index based on the 5R framework, resulting in a CI of 53% or 0.53. The CI value from the case study indicates a moderate level of circularity and significant potential for material utilisation, recycling, and energy recovery during production. Finally, a System Dynamics model is developed using VENSIM to simulate the temporal evolution of material reuse and recycling rates under various intervention scenarios. The integrated 5R framework is operationalised through dynamic modelling, enabling a predictive assessment of the process’s sustainability over a 12-month horizon. Data from secondary sources and several case studies were used to validate the System Dynamics model. Through sensitivity and scenario analyses, the model evaluates short-medium term impacts on waste reduction and energy recovery from various CE intervention levels: 10%, 30%, 50%, 70%, and 90%. Simulation results show substantial material reductions, especially for CE intervention levels above 50%. Virgin material demand decreases significantly at 90% intervention, resulting in more than 3.15 million tons of reduced material. Energy recovery almost doubles on the lower levels of CE intervention, levels of 10% to 50%CE intervention, reducing reliance on non-coking coal and lowering overall carbon dioxide emissions. The strategic implications of CE interventions at varying levels have many benefits, including a reduction in virgin material use, enhanced resource productivity, and lower fuel consumption.The HSIM-CE-SD approach developed in this research provides both a methodological innovation and a practical tool for sustainability improvement. By capturing both the structural complexity and dynamic behaviour of material interactions within the coal-based DRI system, this work bridges the gap between sustainability theory and industry practice in the metallurgical sector. OWSD (Organisation for Women in Science for the Developing World) Fund Reservation No: 3240318607 Industrial and Systems Engineering PhD (Industrial Engineering) Unrestricted Faculty of Engineering, Built Environment and Information Technology SDG-12: Responsible consumption and production SDG-11: Sustainable cities and communities 2026-02-18T13:43:22Z 2026-02-18T13:43:22Z 2026-05-21 2025-09-30 Thesis * A2026 http://hdl.handle.net/2263/108417 10.25403/UPresearchdata.31359781 en © 2024 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | UCTD Sustainable Development Goals (SDGs) Circular economy Direct reduction iron System dynamics Sustainability Modelling for a sustainable coal-based direct reduction iron production using an integrated approach of circular economy and systems thinking for compliance and comprehensiveness and for eco-friendly environmental decision-making |
| title | Modelling for a sustainable coal-based direct reduction iron production using an integrated approach of circular economy and systems thinking for compliance and comprehensiveness and for eco-friendly environmental decision-making |
| title_full | Modelling for a sustainable coal-based direct reduction iron production using an integrated approach of circular economy and systems thinking for compliance and comprehensiveness and for eco-friendly environmental decision-making |
| title_fullStr | Modelling for a sustainable coal-based direct reduction iron production using an integrated approach of circular economy and systems thinking for compliance and comprehensiveness and for eco-friendly environmental decision-making |
| title_full_unstemmed | Modelling for a sustainable coal-based direct reduction iron production using an integrated approach of circular economy and systems thinking for compliance and comprehensiveness and for eco-friendly environmental decision-making |
| title_short | Modelling for a sustainable coal-based direct reduction iron production using an integrated approach of circular economy and systems thinking for compliance and comprehensiveness and for eco-friendly environmental decision-making |
| title_sort | modelling for a sustainable coal based direct reduction iron production using an integrated approach of circular economy and systems thinking for compliance and comprehensiveness and for eco friendly environmental decision making |
| topic | UCTD Sustainable Development Goals (SDGs) Circular economy Direct reduction iron System dynamics Sustainability |
| url | http://hdl.handle.net/2263/108417 |