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Environmental Considerations in the Zero-waste Valorisation of Bauxite Residue: A Life Cycle Perspective
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Sustainability Assessment and Management.ORCID iD: 0000-0002-9560-3132
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bauxite residue, also known as red mud, is produced in large quantities as a result of alumina refining (the first stage in aluminium production), and is one of the world’s most abundant and important industrial wastes. As demand for aluminium continues to increase and space to store this residue diminishes, the potential to utilise bauxite residue as a secondary resource is increasingly being considered by the alumina industry. Bauxite residue can be used as a source of iron, aluminium, titanium oxide, scandium and rare earth oxides, or utilised for its bulk properties to create cement clinkers or inorganic polymers. Achieving any of these uses however requires a series of complex valorisation processes, which in turn require inputs of energy and materials. Some bauxite residues also contain trace amounts of naturally occurring radionuclides.

The EU Horizon 2020 MSCA-ETN REDMUD project was set up to investigate the valorisation of bauxite residue in an integrated manner. The ultimate aim of the REDMUD project is to develop environmentally-friendly, zero-waste, integrated processes for extracting valuable materials from bauxite residue and/or utilising it at high volume. This thesis presents the environmental perspective on this aim, taking a life cycle view; that is, taking into account the upstream and downstream impacts, in addition to the direct impacts, which may result from diverting bauxite residue from landfill to the proposed valorisation processes. This involves using Life Cycle Assessment (LCA) approaches to understand the environmental balance between the impact avoided through landfill diversion and the substitution of conventional materials, and the impacts incurred by the use of materials and energy in the valorisation processes themselves. Importantly, the potential ionising radiation impact from naturally occurring radionuclides is also considered from a life cycle perspective for the first time.

A new life cycle impact assessment method for assessing the impacts of naturally occurring radionuclides was developed. In addition, two pieces of research software, designed to overcome the current shortcomings in LCA software with respect to streamlined and prospective LCA studies of emerging technologies are presented as part of this thesis.

The potential hotspots of environmental impact in a single step valorisation process, the production of high bauxite residue content inorganic polymers, were identified. The results identify the high temperature processing of bauxite residue, in order to transform it into a reactive precursor capable of forming solid inorganic polymers, as a hotspot of environmental impact across a range of environmental impact measures. The production of alkaline activating solutions (the other reagent in the polymerisation reaction) also represented a hotspot of environmental impact. These hotspots were used to identify possible future research directions for this process, which have the potential to reduce the environmental impact of this valorisation process.

Finally it was shown that even in the absence of a detailed and quantified system description, qualitative approaches based on life cycle thinking can be usefully applied to identify important aspects on both sides of the environmental balance between the impacts avoided and the impacts incurred in waste valorisation. Chemical reaction products, chemical synthesis, thermal and mechanical energy are highlighted as potential sources of environmental impact. A case study, looking at the combined extraction of iron and production of inorganic polymers from bauxite residue was used to demonstrate the validity of these qualitative approaches. This study also demonstrated that combining the extraction of iron and inorganic polymers is vital in order to yield a net environmental benefit in terms of climate change.

This thesis provides an initial step on the road towards the environmentally sustainable valorisation of bauxite residue, as well as the analytical tools and additional impact assessment measures required to ensure that this journey can be continued, both within the REDMUD project and beyond.

Abstract [sv]

Bauxitrester, även känt som rödslam, eller bauxitslam (eng: red mud), produceras i stora mängder vid förädling av bauxit till aluminiumoxid och är ett av världens mest rikligt förekommande och viktiga industriella avfall. Eftersom efterfrågan på aluminium fortsätter att öka och utrymme för att lagra detta avfall blir allt mer begränsat, överväger industrin alltmer möjligheten att utnyttja bauxitrester som en sekundär resurs. Bauxitrester kan användas som en källa till utvinning av järn, aluminium, titanoxid, scandium- och sällsynta jordartsmetalloxider eller utnyttjas för dess bulkegenskaper för att tillverka cementklinkers eller geopolymerer (eng: inorganic polymers). För att uppnå något av dessa användningsområden krävs emellertid en rad komplexa valoriseringsprocesser, som i sin tur kräver användning av energi och material. Vissa bauxitrester innehåller också spårmängder av naturligt förekommande radionuklider.EU:s Horizon 2020 MSCA-ETN REDMUD-projekt inrättades för att undersöka möjligheter för valorisering av bauxitrester på ett integrerat sätt. Det slutgiltiga målet med REDMUD-projektet är att utveckla miljövänliga, avfallsfria, integrerade processer för att extrahera värdefulla material från bauxitrester och/eller utnyttja det i stora volymer. Avhandlingen behandlar detta syfte ur miljösynpunkt och med ett livscykelperspektiv; det vill säga med hänsyn till den uppströms- och nedströms miljöpåverkan som, utöver de direkta effekterna, kan uppstå då bauxitrester flyttas från deponi till de föreslagna valoriseringsprocesserna. Det innebär att man använder Livscykelanalys (LCA) för att förstå balansen mellan å ena sidan miljöpåverkan som undviks genom minskad deponering och substitution av konventionella material och å andra sidan den ytterligare miljöpåverkan som användningen av material och energi i valoriseringsprocesserna medför. Det är viktigt att den potentiella joniserande strålningseffekten från naturligt förekommande radionuklider också bedöms från ett livscykelperspektiv för första gången.En ny metod för miljöpåverkansbedömning i LCA av effekterna av naturligt förekommande radionuklider har utvecklats. Dessutom presenteras två nyutvecklade mjukvaror för LCA forskning, utformade för att övervinna de nuvarande begränsningarna i tillgänglig LCA-mjukvara med avseende på förenklad ochframåtblickande LCA-studier av framväxande teknologier som en del av denna avhandling.Potentiella miljömässiga hotspots i en enstegs valoriseringsprocess, produktion av geopolymerer med hög andel bauxitrester, identifierades. Resultaten visar att högtemperaturbehandling av bauxitrester, för att omvandla dessa till en reaktiv prekursor som kan bilda fasta geopolymerer, är en hotspot för en rada olika kategorier av miljöpåverkan. Produktionen av alkalisk aktivator (eng: alkaline activating solution) (det andra reagenset i polymerisationsreaktionen) utgjorde också en hotspot av miljöpåverkan. Dessa hotspots användes för att identifiera möjliga framtida forskningsvägar för denna process, som har potential att minska miljöpåverkan av denna valoriseringsprocess.Slutligen visades att även om det saknas en detaljerad och kvantifierad systembeskrivning kan kvalitativa tillvägagångssätt baserat på livscykeltänkande med fördel användas för att identifiera viktiga aspekter på båda sidor av balansen mellan den miljöpåverkan som undviks och den som uppstår vid avfallsvalorisering . Kemiska reaktionsprodukter, kemisk syntes, termisk och mekanisk energi lyfts fram som potentiella källor till miljöpåverkan. En fallstudie av den kombinerade utvinningen av järn och produktion av geopolymerer från bauxitrester användes för att visa giltigheten av dessa kvalitativa metoder. Denna studie visade också att en kombination av utvinning av järn och tillverkning av geopolymerer är avgörande för att ge en netto miljönytta med avseende på klimatpåverkan.Denna avhandling redogör för ett första steg på vägen mot en miljömässigt hållbar valorisering av bauxitrester, samt de analytiska verktygen och de ytterligare metoder för miljöpåverkansbedömning som krävs för att säkerställa att denna utveckling kan fortsätta, både inom REDMUD-projektet och bortom det.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. , p. 77
Series
TRITA-ABE-DLT ; 1835
Keywords [en]
Life Cycle Assessment (LCA), bauxite residue, waste valorisation, Naturally Occurring Radioactive Materials (NORM), Life Cycle Thinking, LCA software, Circular Economy
Keywords [sv]
Livscykelanalys (LCA), bauxitrest, avfallsvalorisering, naturligt förekommande radioaktiva ämnen (NORM), livscykeltänkande, LCA-programvara, cirkulär ekonomi
National Category
Environmental Sciences
Research subject
Planning and Decision Analysis
Identifiers
URN: urn:nbn:se:kth:diva-239389ISBN: 978-91-7873-004-9 (print)OAI: oai:DiVA.org:kth-239389DiVA, id: diva2:1264889
Public defence
2019-01-07, F3, Lindstedtsvägen 26, Stockholm, 13:00 (English)
Opponent
Supervisors
Projects
REDMUD Project
Funder
EU, Horizon 2020, 636876
Note

QC 20181122

Available from: 2018-11-22 Created: 2018-11-21 Last updated: 2018-11-22Bibliographically approved
List of papers
1. A framework for including enhanced exposure to naturally occurring radioactive materials (NORM) in LCA
Open this publication in new window or tab >>A framework for including enhanced exposure to naturally occurring radioactive materials (NORM) in LCA
2017 (English)In: The International Journal of Life Cycle Assessment, ISSN 0948-3349, E-ISSN 1614-7502, Vol. 22, no 7, p. 1078-1095Article in journal (Refereed) Published
Abstract [en]

Purpose Despite advances in the development of impact categories for ionising radiation, the focus on artificial radionuclides produced in the nuclear fuel cycle means that the potential impacts resulting from increased exposure to naturally occurring radioactive materials (NORM) are still only covered to a limited degree in life cycle assessment (LCA). Here, we present a potential framework for the inclusion of the exposure routes and impact pathways particular to NORM in LCA. Methods We assess the potential magnitude of enhanced NORM exposure, particularly in light of the potential use of NORM residues in building materials, and set out the potential exposure routes that may exist. We then assess the current state of the art, in terms of available fate, exposure and damage models, both within and outside of the LCA sphere. Finally, these exposure routes and modelling techniques are combined in order to lay out a potential framework for NORM assessment in LCA, both in terms of impact on humans and ecosystems. Results and discussion Increased exposure to NORM radionuclides can result either from their release to the environment or their proximity to humans as they reside in stockpiles, landfills or products. The exposure route via products is considered to be increasingly significant in light of current attempts to incorporate technologically enhanced NORMs (TENORM) including bauxite residue into building materials, by groups such as the ETN-MSCA REDMUD project. Impact assessment models for NORM exposure are therefore required to avoid potential burden shifting in the assessment of such TENORM products. Models describing the fate of environmental releases, the exhalation of radon from building products and the shielding effects on landfills/stockpiles are required to assess potential exposure. Subsequently, models relating exposure to radiation sources and the effective internal and external dose received by receptors are required. Finally, an assessment of the damage caused to the receptors is desirable. Conclusions A sufficient suite of currently existing and internationally recognised models exist that can, with varying degrees of modification, form the building blocks of a comprehensive NORM characterisation method for LCA. The challenge ahead lies in consolidating these models, from disparate fields, into a coherent and generally applicable method for the assessment of enhanced NORM exposure in LCA.

Place, publisher, year, edition, pages
Springer, 2017
Keywords
Ionising radiation, LCIA, Naturally occurring radioactivematerial, NORM, TENORM, Impact assessment model
National Category
Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-197922 (URN)10.1007/s11367-016-1218-2 (DOI)000403557600007 ()2-s2.0-84996487013 (Scopus ID)
Projects
MSCA-ETN REDMUD
Funder
EU, Horizon 2020, 636876
Note

QC 20170109

Available from: 2016-12-09 Created: 2016-12-09 Last updated: 2018-11-22Bibliographically approved
2. Impact assessment of enhanced exposure from Naturally Occurring Radioactive Materials (NORM) within LCA
Open this publication in new window or tab >>Impact assessment of enhanced exposure from Naturally Occurring Radioactive Materials (NORM) within LCA
Show others...
2018 (English)In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 172, p. 2824-2839Article in journal (Refereed) Published
Abstract [en]

The potential impact of ionising radiation from enhanced exposure to Naturally Occurring Radioactive Materials (NORM) to humans and the environment is not currently accounted for sufficiently in Life Cycle Assessment (LCA). Here we present midpoint and endpoint characterisation factors resulting from the implementation of impact assessment models for human health and ecosystems for NORM exposure. These models build upon existing fate, exposure and effect models from the LCA and radiological literature. The newly developed models are applied to a theoretical study of the utilisation of bauxite residue, a by-product of alumina processing enriched in natural radionuclides, in building materials. The ecosystem models have significant sensitivity to uncertainties surrounding the differential environmental fate of parent and daughter radionuclides that are produced as a part of decay chains, and to assumptions regarding long term releases from landfill sites. However, conservative results for environmental exposure suggest that in addition to landfill of materials, power consumption (burning coal and mining uranium) is a potentially significant source of radiological impact to the environment. From a human perspective, exposure to NORM in the use phase of building materials is the dominant source of impact, with environmental releases of nuclides playing a comparatively minor role. At an endpoint level, the impact of NORM exposure is highly significant in comparison to other impact categories in the area of protection of human health. The dose increase is of an order of magnitude comparable to lifestyle factors. The results highlight the importance within LCA of having sufficient impact assessment models to capture all potential impacts, such that issues of burden shifting between impact measures can be captured, interpreted and resolved in the optimisation of product systems.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Bauxite residue, Burden shifting, Construction materials, LCA impact category, NORM, Agronomy, Economics, Elongation, Environmental impact, Environmental management, Fertilizers, Gas emissions, Grain growth, Greenhouse gases, Information management, Nitrogen, Nitrogen compounds, Nitrogen fertilizers, Proteins, Sustainable development, Urea, Energy indexes, GHG emission, Grain quality, N fertilizers, Triticum, Grain (agricultural product)
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-223168 (URN)10.1016/j.jclepro.2017.11.131 (DOI)000423002200135 ()2-s2.0-85038867547 (Scopus ID)
Note

QC 20180912

Available from: 2018-02-28 Created: 2018-02-28 Last updated: 2018-11-22Bibliographically approved
3. Lcopt - An interactive tool for creating fully parameterised Life Cycle Assessment (LCA) foreground models
Open this publication in new window or tab >>Lcopt - An interactive tool for creating fully parameterised Life Cycle Assessment (LCA) foreground models
2017 (English)In: The Journal of Open Source Software, ISSN 2475-9066, Vol. 2, no 16, p. 339-Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Open Source Initiative, 2017
National Category
Software Engineering
Identifiers
urn:nbn:se:kth:diva-232078 (URN)10.21105/joss.00339 (DOI)
Note

QC 20180717

Available from: 2018-07-10 Created: 2018-07-10 Last updated: 2018-11-21Bibliographically approved
4. Computer vision for LCA foreground modelling – an initial pipeline and proof of concept software, lcopt-cv
Open this publication in new window or tab >>Computer vision for LCA foreground modelling – an initial pipeline and proof of concept software, lcopt-cv
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Purpose

The majority of LCA studies begin with the drawing of a process flow diagram, which then needs to be translated manually into an LCA model. This study presents an initial image processing pipeline, implemented in an open source software package, called lcopt-cv, which can be used to identify the boxes and links in a photograph of a hand-drawn process flow diagram and automatically create an LCA foreground model.

Methods

The computer vision pipeline consists of a total of fifteen steps, beginning with loading the image file and conversion to greyscale. The background is equalised, then the foreground of the image is extracted from the background using thresholding. The lines are then dilated and closed to account for drawing errors. Contours in the image are detected and simplified, and rectangles (contours with four corners) are identified from the simplified contours as ‘boxes’. Links between these boxes are identified using a flood-filling technique. Heuristic processing, based on knowledge of common practice in drawing of process flow diagrams is then performed to more accurately identify the typology of the identified boxes and the direction of the links between them.

Results and Discussion

The performance of the image processing pipeline was tested on four different flow charts of increasing difficulty: A simple flow chart drawn in MS PowerPoint and saved as an image, followed by three photographs of hand-drawn flow charts. These consisted of a simple flow chart, a complex flow chart and a deliberately difficult example with merged lines. A set of default parameters for the pipeline was developed through trial and error. With minor tweaks to the default parameters, possible through the user interface of lcopt-cv, all of the flow charts were capable of being correctly processed and turned into LCA models. These models were successfully exported to further open source LCA software packages (lcopt and Brightway) to be analysed.

Conclusions

This study demonstrates that it is possible to generate a fully functional LCA model from a picture of a flow chart. This has potentially important implications not only for LCA practitioners as a whole, but in particular for the teaching of LCA. Skipping the steep learning curve required by most LCA software packages allows teachers to focus on important LCA concepts, while participants maintain the benefits of experiential learning by doing a ‘real’ LCA.

Keywords
Process flow diagram, Computer vision, LCA foreground modelling, Open-source software
National Category
Computer Vision and Robotics (Autonomous Systems) Environmental Sciences
Research subject
Industrial Ecology
Identifiers
urn:nbn:se:kth:diva-239340 (URN)
Note

QC 20181122

Available from: 2018-11-21 Created: 2018-11-21 Last updated: 2018-11-22Bibliographically approved
5. Identifying hotspots of environmental impact in the development of novel inorganic polymer paving blocks from bauxite residue
Open this publication in new window or tab >>Identifying hotspots of environmental impact in the development of novel inorganic polymer paving blocks from bauxite residue
Show others...
2018 (English)In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 138, p. 87-98Article in journal (Refereed) Published
Abstract [en]

High bauxite residue content inorganic polymer paving blocks have the potential not only to provide a solution to the ongoing waste management issues faced by the alumina sector, but to simultaneously provide low environmental impact building materials to the construction sector. In order to realise the potential of this emerging technology, it is important to understand where the hotspots of environmental impact are likely to occur, and identify routes to reduce this impact, at an early stage of development. In this study we use anticipatory Life Cycle Assessment (LCA) to identify hotspots of environmental impact in the production of paving blocks made from inorganic polymers derived from bauxite residue. This technology has only been demonstrated at laboratory scale; however, production was modelled at industrial scale. The bauxite residue is fired in a rotary kiln in the presence of a carbon and silica source, in order to create a reactive precursor. When mixed with an alkali the precursor forms a solid block. Our results identify the firing process as the major hotspot of environmental impact, primarily due to the combustion of fossil fuels in the rotary kiln. Steps to reduce the impact of the firing step or to reduce the amount of fired precursor used in the final paving block are suggested as routes for future impact reduction. Optimisation of the environmental aspects of these building materials at an early stage in their development could lead to a promising future for high-volume bauxite residue valorisation at low environmental cost.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Life cycle assessment, Inorganic polymers, Bauxite residue, Secondary resources, Waste management, Waste valorisation
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-235551 (URN)10.1016/j.resconrec.2018.07.006 (DOI)000444789400010 ()2-s2.0-85050227042 (Scopus ID)
Note

QC 20181002

Available from: 2018-10-02 Created: 2018-10-02 Last updated: 2018-11-30Bibliographically approved
6. Using Life Cycle Thinking to assess the sustainability benefits of complex valorization pathways for Bauxite Residue: the case of the MSCA-ETN REDMUD Project
Open this publication in new window or tab >>Using Life Cycle Thinking to assess the sustainability benefits of complex valorization pathways for Bauxite Residue: the case of the MSCA-ETN REDMUD Project
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Bauxite residue, the main waste product of alumina production, is a potentially valuable secondary resource. The MSCA-ETN REDMUD project aims to develop environmentally friendly technologies to realize this value, by extracting valuable materials (aluminium, iron, titanium, scandium, rare earth elements) or utilizing it in construction applications. Simply utilizing a waste product as an input is not however sufficient to claim that a process is environmentally friendly; the processes developed must be demonstrably better for the environment, from a life cycle perspective, than business as usual. The earlier in the research and development process that environmental information can be taken into account, the more impact it can have on decision making. In this study we demonstrate that Life Cycle Thinking approaches can provide actionable environmental information at an early stage in the research process, and that in doing so it can help steer early stage technology development towards overall improved industry environmental performance. Knowledge of the potential environmental benefit from displacing different materials can help identify primary or additional targets, for example the use of metal extraction residues for construction materials. A high level ‘red flags’ assessment of the relative environmental impact of inputs to valorization processes and the products they displace can be used to identify problematic inputs and processes in the absence of quantitative details. Finally, once preliminary quantitative data are available for a process, streamlined Life Cycle Assessment can be used to calculate the environmental balance of a process, and identify specific hotspots of environmental impact.

Keywords
Bauxite residue, red mud, valorization, sustainability, life cycle thinking, life cycle assessment
National Category
Environmental Sciences
Research subject
Industrial Ecology
Identifiers
urn:nbn:se:kth:diva-239341 (URN)
Projects
REDMUD Project
Funder
EU, Horizon 2020, 636876
Note

QC 20181122

Available from: 2018-11-21 Created: 2018-11-21 Last updated: 2018-11-22Bibliographically approved

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