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Waste, Volume 1, Issue 4 (December 2023) – 9 articles

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14 pages, 4989 KiB  
Article
Recovery of Magnetic Particles from Wastewater Formed through the Treatment of New Polycrystalline Diamond Blanks
by Saliha Keita, Srecko Stopic, Ferdinand Kiessling, Tatjana Volkov Husovic, Elif Emil Kaya, Slavko Smiljanic and Bernd Friedrich
Waste 2023, 1(4), 993-1006; https://doi.org/10.3390/waste1040057 - 08 Dec 2023
Viewed by 847
Abstract
Cobalt’s pivotal role in global development, especially in lithium-ion batteries, entails driving increased demand and strengthening global trading networks. The production of different waste solutions in metallurgical operations requires the development of an environmentally friendly research strategy. The ultrasonic spray pyrolysis and hydrogen [...] Read more.
Cobalt’s pivotal role in global development, especially in lithium-ion batteries, entails driving increased demand and strengthening global trading networks. The production of different waste solutions in metallurgical operations requires the development of an environmentally friendly research strategy. The ultrasonic spray pyrolysis and hydrogen reduction method were chosen to produce nanosized magnetic powders from waste solution based on iron and cobalt obtained during the purification process of used polycrystalline diamond blanks. With specific objectives focused on investigating the impact of reaction temperature and residence time on the morphology, chemical composition, and crystal structure of synthesized nanosized cobalt powders, our research involved 15 experimental runs using two reactors with varying residence times (7.19 s and 23 s) and distinct precursors (A, B, and C). Aerosol droplets were reduced at 600 to 900 °C with a flow rate of 3 L/min of argon and hydrogen (1:2). Characterization via scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction revealed that higher temperatures influenced the spherical particle morphology. Altering cobalt concentration in the solution impacted the particle size, with higher concentrations yielding larger particles. A short residence time (7.9 s) at 900 °C proved optimal for cobalt submicron synthesis, producing spherical particles ranging from 191.1 nm to 1222 nm. This research addresses the environmental significance of recovering magnetic particles from waste solutions, contributing to sustainable nanomaterial applications. Full article
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16 pages, 2406 KiB  
Article
Enhanced Extraction of Carotenoids from Tomato Industry Waste Using Menthol/Fatty Acid Deep Eutectic Solvent
by Despoina Vlachoudi, Theodoros Chatzimitakos, Vassilis Athanasiadis, Eleni Bozinou and Stavros I. Lalas
Waste 2023, 1(4), 977-992; https://doi.org/10.3390/waste1040056 - 27 Nov 2023
Cited by 1 | Viewed by 935
Abstract
This study aimed to explore the efficiency of hydrophobic deep eutectic solvents (HDESs) composed of menthol and fatty acids for extracting carotenoids from tomato by-products. A selection of nine different HDESs and fatty acid mixtures were prepared and evaluated for their carotenoid extraction [...] Read more.
This study aimed to explore the efficiency of hydrophobic deep eutectic solvents (HDESs) composed of menthol and fatty acids for extracting carotenoids from tomato by-products. A selection of nine different HDESs and fatty acid mixtures were prepared and evaluated for their carotenoid extraction potential. The highest extraction yield was obtained with menthol/hexanoic acid 2:1 (94.5 ± 3.3 μg CtE/g dm), demonstrating the influence of the specific composition of DES components on extraction efficiency. An optimization process employing a Box–Behnken design was conducted to identify the optimal extraction conditions. The solvent-to-solid ratio, extraction time, and temperature were studied, resulting in an extraction yield increase of up to 48.5% under optimized conditions (solvent-to-solid ratio of 25:1, extraction time of 90 min, and temperature of 50 °C). Furthermore, potent antioxidant properties, including antiradical activity (63.7 ± 4 μmol AAE/g dm) and reducing power (26.7 ± 1.8 μmol AAE/g dm), were recorded. Comparative analyses with conventional organic solvents (hexane, ethyl acetate, and acetone) highlighted the superiority of HDES in both carotenoid extraction and antioxidant capacity. A color analysis of the extracts showed distinctive color profiles, with the HDES extract displaying higher redness and reduced yellowness compared to organic solvent extracts. Principal component analysis (PCA) and multivariate correlation analysis (MCA) revealed strong correlations between total carotenoid content and antioxidant parameters, underscoring the relationship between carotenoid extraction and antioxidant potential. In conclusion, this study highlights the potential of HDESs, particularly Men/Hex 2:1, as efficient and sustainable solvents for carotenoid extraction. These findings offer valuable insights for the development of innovative and environmentally friendly methods for extracting carotenoids with potential applications in various industries. Full article
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17 pages, 1455 KiB  
Review
A Short Review on Dye-Wastewater Valorization Using Up-Flow Anaerobic Sludge Blanket Reactors
by Ronei de Almeida and Claudinei de Souza Guimarães
Waste 2023, 1(4), 960-976; https://doi.org/10.3390/waste1040055 - 24 Nov 2023
Viewed by 889
Abstract
Dye-containing effluent generated in textile industries is polluting and complex wastewater. It should be managed adequately before its final destination. The up-flow anaerobic blanket (UASB) reactor application is an ecofriendly and cost-competitive treatment. The present study briefly reviews the UASB application for dye-containing [...] Read more.
Dye-containing effluent generated in textile industries is polluting and complex wastewater. It should be managed adequately before its final destination. The up-flow anaerobic blanket (UASB) reactor application is an ecofriendly and cost-competitive treatment. The present study briefly reviews the UASB application for dye-containing wastewater valorization. Bioenergy and clean-water production potential during dye-containing wastewater treatment are emphasized to promote resource recovery in textile industries. Hydraulic retention time (HRT), organic loading rate (OLR), pH, temperature, and hydraulic mixing influence sludge granulation, microbial activity, and dye removal. HRT and OLR ranges of 6–24 h and 1–12 kg m−3 d−1 of chemical oxygen demand (COD) at a mesophilic temperature (30–40 °C) are recommended for efficient treatment. In these conditions, efficiencies of color and COD of 50–97% and 60–90% are reported in bench-scale UASB studies. Complex dye structures can hinder biomineralization. Pretreatment may be necessary to reduce dye concentration. Carbon-source and redox mediators are added to the UASB reactor to expedite kinetic reactions. A biogas yield of 1.48–2.70 L d−1 in UASB, which treats dye-containing effluents, is documented. Cotreatment of dye wastewater and locally available substrate could increase biogas productivity in UASB reactors. Organic waste generated in the textile industry, such as dye sludge, cotton, and starch, is recommended to make cotreatment cost competitive. Bioenergy production and water reuse allow environmental and economic benefits. Studies on combined systems integrating UASB and membrane processes, such as ultrafiltration and nanofiltration, for the production of reusable water and pretreatment of wastewater and sludge for improvements in biogas production might realize the complete potential for resource recovery of UASB technology. UASB bioenergy usage for integrated treatment trains can reduce operating costs and assist process sustainability in the textile industry. Full article
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25 pages, 3039 KiB  
Review
A Decade Review of Research Trends Using Waste Materials in the Building and Construction Industry: A Pathway towards a Circular Economy
by Robert Haigh
Waste 2023, 1(4), 935-959; https://doi.org/10.3390/waste1040054 - 20 Nov 2023
Cited by 3 | Viewed by 2016
Abstract
The construction industry is among the most prominent contributors to global resource consumption, waste production, and greenhouse gas emissions. A pivotal step toward mitigating these sectoral impacts lies in the adoption of a circular production and consumption system. The use of alternative waste [...] Read more.
The construction industry is among the most prominent contributors to global resource consumption, waste production, and greenhouse gas emissions. A pivotal step toward mitigating these sectoral impacts lies in the adoption of a circular production and consumption system. The use of alternative waste materials can mitigate landfill accumulation and the associated detrimental environmental effects. To highlight unconventional materials, this study began with a bibliometric assessment via a bibliography analyzis software called “Bibliometrix” (version 4.1.3). The outputs from the analyzis can assist in identifying research trends, gaps in literature and benchmark research performance. The search engine used for sourcing publications was Scopus, using the main criteria as “Waste materials used in building and construction”. The time-period analysed was from 2013 to 2023. The results included publications obtained in journal articles, book chapters and conference proceedings. The assessment reviewed 6238 documents from 1482 sources. The results revealed an array of waste materials; however, rubber, textiles, and ceramics had a significant reduction in research attention. Rubber waste presents promising opportunities in civil concrete construction methods. The preparatory steps of textile fibres in composite materials are frequently disregarded, resulting in structural issues for the end-product. Obstacles persist in ceramic technology due to the absence of transparency, primarily because industry entities closely safeguard proprietary information. While sustainability research often emphasizes emissions, practical trials commonly revolve around integrating materials into current systems. A more comprehensive approach, contemplating the complete lifecycle of materials, could provide deeper insights into fostering sustainable construction practices. Researchers can use these findings when determining trends, research gaps, and future research directions. Full article
(This article belongs to the Special Issue Solid Waste Management and Environmental Protection)
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16 pages, 2935 KiB  
Article
Influences of Management Practices and Methodological Choices on Life Cycle Assessment Results of Composting Mixtures of Biowaste and Green Cuts
by Ben Joseph and Heinz Stichnothe
Waste 2023, 1(4), 919-934; https://doi.org/10.3390/waste1040053 - 12 Nov 2023
Viewed by 630
Abstract
This paper presents an analysis that aimed to quantify the consequences of modelling choices in the life cycle assessment of composting by investigating the influence of composting management practices and the influence of the selected marginal product for substitution. In order to investigate [...] Read more.
This paper presents an analysis that aimed to quantify the consequences of modelling choices in the life cycle assessment of composting by investigating the influence of composting management practices and the influence of the selected marginal product for substitution. In order to investigate the different influencing factors, a set of 11 scenarios were defined. The scenario results revealed that increasing the turning frequency of the input material leads to a Global warming potential (GWP) reduction of approx. 50%. However, there is a trade-off between GWP reduction and increases in other environmental impacts, including acidification potential (AP), ozone formation potential (OFP), and stratospheric ozone depletion potential (ODP). GWP and AP can also be reduced by optimal exhaust gas filter maintenance, although this causes OFP and ODP to increase. The most relevant factor for GWP is the choice of substituted products. When peat for horticulture can be replaced, GWP can be substantially lowered while hardly affecting other environmental impacts. Full article
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18 pages, 6259 KiB  
Article
Amount of Fill Product Residues in Plastic Packagings for Recycling
by Konstantin Schinkel, Bastian Küppers, Sven Reichenbach, Teresa Rohrmeier, Kajetan Müller, Tanja Fell and Sven Sängerlaub
Waste 2023, 1(4), 901-918; https://doi.org/10.3390/waste1040052 - 09 Oct 2023
Viewed by 1390
Abstract
Fill product residues in packagings are equivalent to product losses. They are washed out after sorting and before commencing recycling processes. Not much data have been published about how much fill product is still present in packagings dedicated for recycling. Results are often [...] Read more.
Fill product residues in packagings are equivalent to product losses. They are washed out after sorting and before commencing recycling processes. Not much data have been published about how much fill product is still present in packagings dedicated for recycling. Results are often from laboratory trials. Therefore, several hundred packagings from a sorting plant of a dual system in Germany were analysed to determine the amount of fill product residues. Approximately 10 wt. % of highly viscous fill products in tubes were lost as residue. In the case of packagings that were easy to empty, such as cups, and in the case of low-viscosity fill products, such as water, less than 1 wt. % of the fill products remained in the packagings. The mean amount of residue in relation to clean packaging was 0.9 g residue in 1 g of packaging material (without residue) in tubes and 0.07 g in PET bottles. These values were significantly lower for low-viscosity fill products compared to high-viscosity fill products, as expected. Full article
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17 pages, 1491 KiB  
Article
Valorizing the Input and Output Waste Streams from Three PtX Case Studies in Denmark—Adopting a Symbiotic Approach
by Rikke Lybæk and Tyge Kjær
Waste 2023, 1(4), 884-900; https://doi.org/10.3390/waste1040051 - 06 Oct 2023
Viewed by 1132
Abstract
This study aimed to investigate the waste streams from the production of hydrogen energy carriers from PtX technology and identify how they can be valorized by applying a symbiotic approach to enable greater utilization of the inputs and outputs from such plants. Various [...] Read more.
This study aimed to investigate the waste streams from the production of hydrogen energy carriers from PtX technology and identify how they can be valorized by applying a symbiotic approach to enable greater utilization of the inputs and outputs from such plants. Various electrolysis development projects are under development or in the pipeline in Europe and Denmark, but in many cases, it is not clear how waste streams are emphasized and valued in these projects. Thus, three exploratory case studies (a city, a rural, and an energy hub case) were investigated herein exemplifying state-of-the-art electrolysis projects currently being deployed, with a focus on identifying how and to what extent waste streams are being valorized in these projects and energy system integration is being pursued. Inspired by the industrial symbiosis literature, we analyzed how internal, regional, and long-distance symbiotic collaboration is realized within these cases and found them to be very different in terms of the energy carrier produced, the current development stage, and the access to appropriate energy infrastructure. This paper concludes that the co-location of PtX technology near biogas plants would provide a great opportunity for the integration of the produced energy carriers and waste streams into the existing energy system and, hence, could assist in stabilizing fluctuating renewable energy sources to enable their more efficient use in the energy system. Full article
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24 pages, 7885 KiB  
Review
Mechanical Recycling of Thermoplastics: A Review of Key Issues
by Alae Lamtai, Said Elkoun, Mathieu Robert, Frej Mighri and Carl Diez
Waste 2023, 1(4), 860-883; https://doi.org/10.3390/waste1040050 - 04 Oct 2023
Cited by 1 | Viewed by 3656
Abstract
During the last decade, the consumption of plastics has increased highly in parallel with plastic waste. The transition towards a circular economy is the only way to prevent the environment from landfilling and incineration. This review details the recycling techniques with a focus [...] Read more.
During the last decade, the consumption of plastics has increased highly in parallel with plastic waste. The transition towards a circular economy is the only way to prevent the environment from landfilling and incineration. This review details the recycling techniques with a focus on mechanical recycling of polymers, which is the most known and developed technique in industries. The different steps of mechanical recycling have been highlighted, starting from sorting technologies to the different decontamination processes. This paper covers degradation mechanisms and ways to improve commodity polymers (Polyolefins), engineering polymers (PET, PA6), and bio-sourced polymers (PLA and PHB). Full article
(This article belongs to the Special Issue Solid Waste Management and Environmental Protection)
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19 pages, 1541 KiB  
Review
Overview of the Biotransformation of Limonene and α-Pinene from Wood and Citrus Residues by Microorganisms
by Adama Ndao and Kokou Adjallé
Waste 2023, 1(4), 841-859; https://doi.org/10.3390/waste1040049 - 04 Oct 2023
Viewed by 1917
Abstract
This review provides an overview of the biotransformation of limonene and α-pinene, which are commonly found in wood residues and citrus fruit by-products, to produce high-value-added products. Essential oils derived from various plant parts contain monoterpene hydrocarbons, such as limonene and pinenes which [...] Read more.
This review provides an overview of the biotransformation of limonene and α-pinene, which are commonly found in wood residues and citrus fruit by-products, to produce high-value-added products. Essential oils derived from various plant parts contain monoterpene hydrocarbons, such as limonene and pinenes which are often considered waste due to their low sensory activity, poor water solubility, and tendency to autoxidize and polymerise. However, these terpene hydrocarbons serve as ideal starting materials for microbial transformations. Moreover, agro-industrial byproducts can be employed as nutrient and substrate sources, reducing fermentation costs, and enhancing industrial viability. Terpenes, being secondary metabolites of plants, are abundant in byproducts generated during fruit and plant processing. Microbial cells offer advantages over enzymes due to their higher stability, rapid growth rates, and genetic engineering potential. Fermentation parameters can be easily manipulated to enhance strain performance in large-scale processes. The economic advantages of biotransformation are highlighted by comparing the prices of substrates and products. For instance, R-limonene, priced at US$ 34/L, can be transformed into carveol, valued at around US$ 530/L. This review emphasises the potential of biotransformation to produce high-value products from limonene and α-pinene molecules, particularly present in wood residues and citrus fruit by-products. The utilisation of microbial transformations, along with agro-industrial byproducts, presents a promising approach to extract value from waste materials and enhance the sustainability of the antimicrobial, the fragrance and flavour industry. Full article
(This article belongs to the Special Issue Agri-Food Wastes and Biomass Valorization)
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