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Valorization of Secondary Resources

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A special issue of Sustainability (ISSN 2071-1050). This special issue belongs to the section "Resources and Sustainable Utilization".

Deadline for manuscript submissions: closed (15 January 2023) | Viewed by 11897

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Special Issue Editors

Dr. Ismael Matino

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Guest Editor

ICT-COISP Center of Institute of Communication, lnformation and Perception Technologies TECIP, Scuola Superiore Sant'Anna, 56124 Pisa, Italy
Interests: valorization of secondary material and energy resources; industrial sustainability; circular economy; industrial symbiosis; environmental impact; modelling and simulation; process integration and optimization; monitoring and control; artificial intelligence; machine learning; chemical and industrial engineering; metallurgy
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Dr. Valentina Colla

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Guest Editor

TeCIP Institute, Scuola Superiore Sant’Anna, 56124 Pisa, Italy
Interests: metallurgy; steel; modelling; simulation; sustainability; circular economy
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We are now more than 30 years from the date in which the Brundtland Report, better known as Our Common Future, introduced the concept of sustainable development. The main aim of a sustainable development is to ensure continuous access to natural resources avoiding permanent damages to the environment. According to this principle, the rate of the exploitation of primary resources must be lower or equal to their regeneration and the waste production rate needs to satisfy the ecosystem capacity to absorb them. Following these philosophies, more than 10 years ago the Circular Economy concept was introduced and became a priority in a society that requests ever more amounts of resources. Through its “take-transform-throw-take-transform-throw” recursive principle, the Circular Economy suggests the importance of resources optimization through the minimization of wastes and the valorization of secondary resources.

Secondary resources derive from wastes and residues of all industrial and public operations. Not only solid wastes are included but also wastewater and process off-gases that can be valorized through the application of process integration and industrial symbiosis solutions involving private and public entities. The valorization of any kind of secondary resource can lead to significant advantages in terms of waste prevention and reduction.

The valorization of secondary resources can be carried out through, for example, ad-hoc treatments and/or processes devoted to the sorting of particular fractions to be used as secondary raw materials or for their conversion in valuable materials/products or energy sources. Noticeable advantages can be obtained in terms of environmental, energetic, economic and social impacts. However, the valorization of secondary resources is sometimes hampered by several factors that are related to the nature and composition of wastes/residues as well as to social and political issues. For instance, the valorization of wastes and residues can be difficult if they contain dangerous or toxic compounds or if the required treatment processes generate significant emissions or are not environmental-friendly.

In addition, public awareness as well as the availability of adequate skills and training activities for the workers of both companies and public bodies can help to create a “culture” concerning by-products reuse and recycling as well as recovery of valuable material from wastes. Finally, progress in existing legislations can support removal of unnecessary obstacles and barriers that can slow the evolution towards a zero-waste society.

This Special Issue is focused on novel treatments, processes, and solutions for a sustainable valorization of secondary resources coming from both industrial and public fields as well as advanced techniques linked to the concept of Industry 4.0, such as innovative machine-learning-based modelling, data analytics tools, and optimization strategies, enabling an interdisciplinary approach to the waste minimization and resource efficiency maximization. In addition, the Special Issue also aims to cover social and political barriers and related pioneering solutions related to the secondary resources management and valorization.

Dr. Ismael Matino
Prof. Dr. Valentina Colla
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 development
circular economy
industrial symbiosis
innovations on reuse, recycle, recovery and regeneration of wastes and residues
integrated management of urban waste
differentiated waste collection chains (e.g., paper, plastics, glass, metals)
novel technologies for organic waste fraction treatment and for composting
biomass valorization
sustainable processes for the management of waste of electric and electronic equipments
end-of-life batteries management
rare earth elements recovery
toxic and hazardous waste management and treatments
construction and demolition waste recovery
pioneering solutions for waste sorting
green innovative systems for waste-to-energy
wastewater management (e.g. treatment, reuse, recycle)
industrial and public bodies symbiosis
process integration
modelling and simulation tools for improving material and energy resources efficiency
application of machine learning techniques and data analytics for improving secondary resources management
advanced optimization strategies for synergic miminization of wastes and maximization of recoveries
environmental-driven economy platforms
social and economic impacts of secondary resources valorization
ground-breaking solutions to social and political barriers for the implementation of resource efficiency and industrial symbiosis solutions
skills and training activities promoting circular economy and industrial symbiosis-based culture in industry

Published Papers (6 papers)

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Research

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24 pages, 4396 KiB

Open AccessArticle

Utilization of Synthetic Steel Gases in an Additively Manufactured Reactor for Catalytic Methanation

by Alexander Hauser, Alexander Feldner, Peter Treiber, Fabian Grimm and Jürgen Karl

Sustainability 2023, 15(9), 7652; https://doi.org/10.3390/su15097652 - 06 May 2023

Cited by 1 | Viewed by 1169

Abstract

The path to European climate neutrality by 2050 will require comprehensive changes in all areas of life. For large industries such as steelworks, this results in the need for climate-friendly technologies. However, the age structure of existing steelworks makes transitional solutions such as carbon capture, utilization and storage (CCUS) necessary as short-term measures. Hence, a purposeful option is the integration of technical syntheses such as methanation into the overall process. This work summarizes hydrogen-intensified methanation experiments with synthetic steel gases in the novel additively manufactured reactor ‘ADDmeth1’. The studies include steady-state operating points at various reactor loads. Blast furnace gas (BFG), basic oxygen furnace gas (BOFG) and three mixtures of these two gases serve as carbon sources. The methanation achieved methane yields of 93.5% for BFG and 95.0% for BOFG in the one-stage once-through setup. The results suggest a kinetic limitation in the case of BFG methanation, while an equilibrium limitation is likely for BOFG. There is a smooth transition in all respects between the two extreme cases. The reaction channel inlet temperature

ϑ_{i n}

showed a large influence on the reactor ignition behavior. By falling below the threshold value, a blow-off occurred during experimental operation. By means of a simulation model, practical operating maps were created which characterize permissible operating ranges for

ϑ_{i n}

as a function of the gas composition and the reactor load. Full article

(This article belongs to the Special Issue Valorization of Secondary Resources)

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14 pages, 2555 KiB

Open AccessArticle

New Glass Ceramic Materials Obtained from Cathode Ray Tubes Glass Wastes and Fly Ash

by Cosmin Vancea, Giannin Mosoarca, Simona Popa, Mircea Dan and Sorina Boran

Sustainability 2023, 15(4), 3021; https://doi.org/10.3390/su15043021 - 07 Feb 2023

Cited by 2 | Viewed by 1253

Abstract

This paper presents an alternative way to recycle cathode ray tube glass waste, together with fly ash and kaolin, into new glass ceramic materials. The samples were obtained using three firing temperatures: 700, 800, and 900 °C. The effect of the fly ash/CRT waste ratio upon the materials’ firing shrinkage, apparent density, apparent and total porosity, chemical stability, and compression strength was investigated. The firing shrinkage used as a dimensional stability parameter, a firing shrinkage range between 2.19–8.18%, was positively influenced by the waste mix amount. The apparent density of the obtained materials is positively affected by the heat treatment temperature, rising from 2.09 to 2.93 (g·cm⁻³), while the apparent porosity decreases with the increase of the firing temperature from 6.08 to 2.24 %. All the studied glass ceramics show very good chemical stability and complete immobilization of the Pb²⁺ and Ba²⁺ ions in the glass ceramic matrix. The compression strength of the sintered materials ranges between 1.42–11.83 (N·mm⁻²), being positively influenced by the kaolin amount and negatively influenced by porosity. The obtained results confirm the viability of the proposed alternative to use CRT waste and fly ash together with kaolin to obtain glass ceramic materials that can be used for outdoor paving applications. Full article

(This article belongs to the Special Issue Valorization of Secondary Resources)

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16 pages, 2716 KiB

Open AccessArticle

Optimizing Leaching of Rare Earth Elements from Red Mud and Spent Fluorescent Lamp Phosphors Using Levulinic Acid

by Tao Jiang, Sarabjot Singh, Kathleen A. Dunn and Yanna Liang

Sustainability 2022, 14(15), 9682; https://doi.org/10.3390/su14159682 - 05 Aug 2022

Cited by 2 | Viewed by 1700

Abstract

Although various hydrometallurgical and solvometallurgical efforts have been made to extract REEs from end-of-life (EoL) products and waste, a systematic and statistical analysis of the impacts of leaching parameters to optimize the leaching process using organic acids is necessary, but lacking in the literature. This study employed the response surface methodology to develop mathematical models for optimal leaching by levulinic acid (LevA) of REEs in two waste materials, namely red mud and spent fluorescent lamp phosphors. The established models exhibited excellent statistical properties, in terms of significance, fitting, prediction, and error distribution. For red mud, the optimal conditions of liquid-to-solid ratio (L/S; v/w) of 40, temperature of 70 °C, and duration of 60 h led to 100% leaching of REEs excluding Sc. At the same L/S and temperature, >98.7% of REEs were leached from fluorescent phosphors after 96 h. The SEM–EDS analysis of the waste materials revealed and confirmed morphological and compositional changes after leaching under the optimal conditions. Full article

(This article belongs to the Special Issue Valorization of Secondary Resources)

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12 pages, 1806 KiB

Open AccessEditor’s ChoiceArticle

Utilization of Organic Mixed Biosludge from Pulp and Paper Industries and Green Waste as Carbon Sources in Blast Furnace Hot Metal Production

by Tova Jarnerud, Andrey V. Karasev, Chuan Wang, Frida Bäck and Pär G. Jönsson

Sustainability 2021, 13(14), 7706; https://doi.org/10.3390/su13147706 - 09 Jul 2021

Cited by 4 | Viewed by 2102

Abstract

A six day industrial trial using hydrochar as part of the carbon source for hot metal production was performed in a production blast furnace (BF). The hydrochar came from two types of feedstocks, namely an organic mixed biosludge generated from pulp and paper production and an organic green waste residue. These sludges and residues were upgraded to hydrochar in the form of pellets by using a hydrothermal carbonization (HTC) technology. Then, the hydrochar pellets were pressed into briquettes together with commonly used briquetting material (in-plant fines such as fines from pellets and scraps, dust, etc. generated from the steel plant) and the briquettes were top charged into the blast furnace. In total, 418 tons of hydrochar briquettes were produced. The aim of the trials was to investigate the stability and productivity of the blast furnace during charging of these experimental briquettes. The results show that briquettes containing hydrochar from pulp and paper industries waste and green waste can partially be used for charging in blast furnaces together with conventional briquettes. Most of the technological parameters of the BF process, such as the production rate of hot metal (<1.5% difference between reference days and trial days), amount of dust, fuel rate and amount of injected coal, amount of slag, as well as contents of FeO in slag and %C, %S and %P in the hot metal in the experimental trials were very similar compared to those in the reference periods (two days before and two days after the trials) without using these experimental charge materials. Thus, it was proven that hydrochar derived from various types of organic residues could be used for metallurgical applications. While in this trial campaign only small amounts of hydrochar were used, nevertheless, these positive results support our efforts to perform more in-depth investigations in this direction in the future. Full article

(This article belongs to the Special Issue Valorization of Secondary Resources)

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13 pages, 3575 KiB

Open AccessArticle

Mechanochemical Treatment of Historical Tungsten Tailings: Leaching While Grinding for Tungsten Extraction Using NaOH

by Jane Mulenshi, Saeed Chehreh Chelgani and Jan Rosenkranz

Sustainability 2021, 13(6), 3258; https://doi.org/10.3390/su13063258 - 16 Mar 2021

Cited by 3 | Viewed by 2066

Abstract

Innovative tungsten (W) extraction techniques are continually being sought because of challenges of low leaching efficiencies, despite using advanced processing units such as autoclaves operating high temperatures and pressures. Compared to conventional leaching, mechanochemical treatment improves the efficiency of leaching. Therefore, in this study, an innovative mechanochemical treatment method, referred to as leaching while grinding (LWG), was employed as a reprocessing option to optimize W recovery from historical tungsten tailings. Experiments were run using the regular two-level factorial design to screen through the four factors of stirrer speed, liquid/solid ratio, temperature, and digestion time to assess their criticality and effects in the LWG process. The stirrer speed and the liquid/solid ratio were the most critical factors in the optimization of W recovery. The maximum W recovery (91.2%) was attained at the highest stirrer speed (410 rpm), low liquid/solid ratio (0.8), long digestion time (6 h), and low leaching temperature (60 °C). The attained low leaching temperature (60 °C) was due to the mechanical activation of scheelite resulting from the simultaneous grinding and leaching. For such low- grade W material, liquid/solid ratio optimizing is critical for maintaining the digestion mixture fluidity, and for environmental and economic sustainability regarding the sodium hydroxide (NaOH) consumption, which was low. Full article

(This article belongs to the Special Issue Valorization of Secondary Resources)

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Review

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20 pages, 2155 KiB

Open AccessReview

Skills Demand in Energy Intensive Industries Targeting Industrial Symbiosis and Energy Efficiency

by Teresa Annunziata Branca, Barbara Fornai, Valentina Colla, Maria Ilaria Pistelli, Eros Luciano Faraci, Filippo Cirilli and Antonius Johannes Schröder

Sustainability 2022, 14(23), 15615; https://doi.org/10.3390/su142315615 - 24 Nov 2022

Cited by 6 | Viewed by 1924

Abstract

Technological development, closely related to the implementation of industrial symbiosis and energy efficiency, affects all areas of energy intensive industries, and involves the whole industrial workforce. This paper deals with a part of the work developed in the early stage of a current Erasmus+ project, which aims at developing an industry-driven and proactive skills strategy to assist the implementation and exploitation of industrial symbiosis and energy efficiency across the energy intensive sectors. The paper presents the current state of workforce in the context of industrial symbiosis and energy efficiency implementations. The most recent literature on the effects of new skills requirement and training needs for the European process industry workforce is analyzed and discussed. In addition, implementation advantages and barriers as well as possible solutions to satisfy ongoing and future skill demands are considered. Through skill integrations and workforce attraction and training, new skills, and greater abilities for working across sector boundaries can be achieved. In addition, policies on green economy and on skills development can enable anticipating labor market changes, by identifying skill requirement impacts. This can be achieved by introducing new training programs, revising existing ones and by monitoring the impact of trainings on the labor market. Full article

(This article belongs to the Special Issue Valorization of Secondary Resources)

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