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Recycling Materials for the Circular Economy—2nd Edition

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A special issue of Sustainability (ISSN 2071-1050).

Deadline for manuscript submissions: 30 September 2024 | Viewed by 3173

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Special Issue Editors

Prof. Dr. Md. Mizanur Rahman

E-Mail Website
Guest Editor

UniSA STEM (Science, Technology, Engineering and Mathematics), University of South Australia, Mawson Lakes, SA 5095, Australia
Interests: soil/geotechnical engineering; bio-cementation; permeable/pavements; sustainable construction material; resource recovery and recycling; energy efficiency/recovery
Special Issues, Collections and Topics in MDPI journals

Dr. Asif Iqbal

E-Mail Website
Guest Editor

UniSA STEM (Science, Technology, Engineering and Mathematics), University of South Australia, Mawson Lakes, SA 5095, Australia
Interests: pavement design; permeable pavement; urban/transport planning; emissions (risks assessment/management); sustainable construction; urban health

Special Issue Information

Dear Colleagues,

Each year, about 90 billion tonnes of primary materials are extracted and used globally, with only nine percent being recycled. The huge quantity of materials wasted due to this is unrecoverable, leading to the depletion of non-renewable natural resources. Again, often the design flaws or non-considerations of reducing the wastes at the beginning imposes a cost of recycling at the end of a process. A circular economy model considers preventing waste (material, pollution, energy, water, etc.) being generated at the beginning of the process by adopting responsible manufacturing/production options, along with the reuse and recycling of the wastes to be incorporated into the system. The lower wastage of materials, thus, leads to more commercially and environmentally sustainable system.

This Special Issue focuses on the recycling phase of the circular economy, at any phase of a system, aiming to reduce the amount of waste generated at the end. It aims to cover optimized design solutions that can ensure economic and environmental efficiency, which is in line with the aims of the journal Sustainability.

In this Special Issue, original research articles and reviews are welcome. Research areas may include (but are not limited to) the following:

Resource recovery and recycling;
Sustainable construction materials;
Water use efficiency;
Energy efficiency/recovery;
Carbon-neutral processes and carbon offset;
Zero waste;
Emission reduction;
Life cycle assessment.

Prof. Dr. Md. Mizanur Rahman
Dr. Asif Iqbal
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sustainability is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

sustainable construction
sustainable materials
zero waste
carbon offset

Published Papers (4 papers)

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Research

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15 pages, 3303 KiB

Open AccessArticle

Techno-Eco-Efficiency Assessment of Using Recycled Steel Fibre in Concrete

by Wahidul K. Biswas, Xihong Zhang, Corey Matters and Mitra Maboud

Sustainability 2024, 16(9), 3717; https://doi.org/10.3390/su16093717 - 29 Apr 2024

Viewed by 436

Abstract

The steel industry is one the three biggest producers of carbon dioxide and it is experiencing technical challenges due to the gradual decrease in the quality of iron ore. Steel is extensively used in the construction industry for structural applications like steel components, while steel fibres are intensively used as additives to concrete in order to improve its performance. It is thus important to consider the use of recycled steel as a replacement for virgin steel in order to address the aforementioned environmental consequences. This paper applies the eco-efficiency framework to determine the economic and environmental implications of the use of recycled fibre in concrete as a replacement for virgin steel. A number of concrete mixes were considered that used virgin, recycled, and treated recycled rebar in concrete. The eco-efficiency framework, which uses a life-cycle assessment approach to calculate the environmental and economic values of concrete mixes in order to determine the portfolio positions of these concrete mixes, was used for comparison purposes and to establish the eco-efficient option(s). Whilst the recovery and recycling process is energy-intensive, the use of recycled steel fibre in reinforced concrete has been found to be eco-efficient and deliver the same level of mechanical performance compared to that obtained using virgin steel fibre. Treating steel fibre could improve its technical performance, but it was found to increase both costs and environmental impacts and was therefore identified as not being eco-efficient. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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14 pages, 2456 KiB

Open AccessArticle

Eco-Efficiency Performance for Multi-Objective Optimal Design of Carbon/Glass/Flax Fibre-Reinforced Hybrid Composites

by Wahidul Biswas and Chensong Dong

Sustainability 2024, 16(7), 2928; https://doi.org/10.3390/su16072928 - 01 Apr 2024

Viewed by 633

Abstract

An eco-efficiency optimisation study on unidirectional carbon/glass fibre-reinforced hybrid composites with natural fibre (i.e., flax) and without flax is presented in this paper. The mechanical performance was assessed by determining the flexural properties obtained via finite element analysis (FEA)-based simulation. Given the required flexural strength, optimal candidate designs were found using a set of design rules and regression analysis, with minimising the cost and weight being the objectives. An eco-efficiency framework was applied to determine the eco-efficient hybrid composites. Life cycle assessment was an indispensable component of the framework as it helped determine the life cycle environmental impacts and costs of the hybrid composite materials. The environmental impacts and cost values were converted to the eco-efficiency portfolios of these composites for both comparison and selection purposes. The hybrid composites using bio-based flax fibre have been found to be eco-efficient in most of the cases due to the avoidance of energy-intensive and expensive reinforcing materials. The environmental impacts of the hybrid composites using flaxes are 12 to 13% less than the ones using no flaxes and the former are 7 to 13% cheaper than the latter, making the flax-based hybrid composites eco-efficient. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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20 pages, 9664 KiB

Open AccessArticle

The Sustainability of Using DuraCrete as Cement Additive to Estuarine Soft Soil Stabilization

by Ali N. Al-Gemeel, Noor Al-Hayo, Dominic E. L. Ong and Yan Zhuge

Sustainability 2024, 16(1), 231; https://doi.org/10.3390/su16010231 - 26 Dec 2023

Viewed by 669

Abstract

Large areas of estuarine deposits exist on the coastal plains of the southeast Queensland coast with a countered depth of up to 30 m. These deposits are categorized as sediments that originated during the Holocene Age. The sediments have not been consolidated or subjected to considerable pressure since the end of the Ice Age. The structure of these deposits consists of large ratios of porosity, causing high soil compressibility, which lowers the bearing capacity of the soils. Therefore, the soils of the region cannot maintain sufficient support for construction loads, and consequent malfunctions could occur in short-term and long-term periods. The objective of this paper is to investigate the suitability of new soil stabilization additives in the southeast Queensland region and the optimum additive content of cementitious materials and an advanced mixing modifier branded as DuraCrete. A combination of Portland cement and DuraCrete was used as a soil additive. Three DuraCrete-to-cement ratios were used: 2%, 3%, and 4% by weight. Soil collected from the Port of Brisbane region was treated by adding the additives as a percentage of its weight; four percentages were considered: 10%, 20%, 25%, and 30% for each combination of additives. The performance of the treated soils was examined under unconfined compression after 28 days of curing. The results revealed that increases in the unconfined compressive strength were detected as DuraCrete was added to the mixtures. For 30% additives, increases of about 15%, 34%, and 17% were detected when DuraCrete was added as 2%, 3%, and 4%, respectively. The results also revealed that 3% DuraCrete content provided significant stabilization compared to 2% and 4% for 25% and 30% additive-treated soils; such behavior was also observed for the specimens of 25% content of additives. Additionally, DuraCrete can be considered a promising material that can be combined with cement to obtain the desired stabilization of soft soils. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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Review

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27 pages, 5868 KiB

Open AccessReview

Sustainable Biocomposites: Harnessing the Potential of Waste Seed-Based Fillers in Eco-Friendly Materials

by Cristiano Fragassa, Felipe Vannucchi de Camargo and Carlo Santulli

Sustainability 2024, 16(4), 1526; https://doi.org/10.3390/su16041526 - 10 Feb 2024

Viewed by 966

Abstract

With the growing concerns over environmental degradation and the increasing demand for sustainable materials, eco-friendly composites have gained considerable attention in recent years. This review paper delves into the promising realm of seed-based fillers, reinforcements and polysaccharidic matrices in the production of biocomposites that are yet focusing on those seeds, which can be considered industrial process waste. Seeds, with their inherent mechanical properties and biodegradability, which are often the waste of production systems, offer a compelling solution to reduce the environmental impact of composite materials. This paper explores the properties of various seeds considered for composite applications and investigates the processing techniques used to incorporate them into composite matrices. Furthermore, it critically analyzes the influence of seed fillers on the mechanical and physical properties of these eco-friendly composites, comparing their performance with traditional counterparts. The environmental benefits, challenges, and limitations associated with seed-based composites from waste seeds are also discussed, as well as their potential applications in diverse industries. Through an assessment of relevant case studies and research findings, this review provides valuable insights into the outlook of seed-based composites as a sustainable alternative in the composite materials landscape, emphasizing their role in promoting a greener and more responsible approach to materials engineering. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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