Waste doi: 10.3390/waste2010007
Authors: Rosa Hernández-López Aurelio López-Malo Ricardo Navarro-Amador Nelly Ramírez-Corona
Sugarcane bagasse (SCB) is a waste product from Mexico’s sugar industry that is generally burned or discarded. It contains around 48% cellulose, representing a significant source of this component from industrial waste. Eugenol is found in clove oil; it has been used for its medicinal and antimicrobial benefits in the food and pharmaceutical industries. This study aims to develop a filtering material using sugarcane bagasse (SCB) and encapsulated eugenol as an antimicrobial agent. The study involves extracting cellulose from SCB using alkaline hydrolysis with ultrasound, followed by forming composite materials encapsulated in alginate with eugenol concentrations from 0 to 1% v/v. These materials were characterized and tested for antimicrobial efficacy. The findings indicate that the cellulose–eugenol–alginate composite displays high eugenol encapsulation efficiency and effective short-term release. In well-diffusion assays, the material showed inhibition halos up to 20.47 mm against S. aureus, suggesting its potential as an eco-friendly alternative to traditional antimicrobial agents in filter materials.
]]>Waste doi: 10.3390/waste2010006
Authors: Souphaphone Soudachanh Alessio Campitelli Stefan Salhofer
One of the largest issues facing countries, particularly emerging nations with high population, production, and consumption growth, is an inadequate waste management system (WMS). This paper analyzes the development of the waste management systems of nine capital cities in the Association of Southeast Asian Nations (ASEAN) region by using a recently developed approach, the Waste Management System–Development Stage Concept. This concept comprises five development stages and various components, including Collection and Transport, Waste Disposal, Energy Recovery, Waste Recycling, and Waste Prevention and Reuse. The findings indicate that in terms of waste collection, waste disposal, and energy recovery, Singapore is at a higher development stage (Stage 5) and is more advanced than other ASEAN cities. For most of the components, Bangkok, Jakarta, Kuala Lumpur, and Manila fall into stages 2 to 4, whereas the early development stages 1 to 3 are present in Bandar Seri Begawan, Hanoi, Phnom Penh, and Vientiane. The results will be used to determine the next steps in developing the WMSs, including the introduction of separate collection for recycling or the installation of a waste-to-energy plant. The environmental impact of each measure will be later assessed using the LCA approach, and the most effective measures shall be identified in future studies.
]]>Waste doi: 10.3390/waste2010005
Authors: Nontobeko Gloria Maphuhla Opeoluwa Oyehan Oyedeji
Inadequate waste management and illegal trash dumping continue to be the leading causes of severe environmental pollution. Human exposure to harmful heavy metals has emerged as a serious health concern on the continent. Some people in Alice, a small town, grow their food in home gardens. They use animal manure and compost derived from soil obtained from landfills to enhance the fertility of the garden soil. Heavy metal heaps in garbage disposals are constantly present, releasing dangerous amounts of metal into the environment. The harmful effects of heavy metals on plants lead to unsanitary conditions and environmental problems. Animals and people who consume these vegetables may also be at risk for health problems. Assessing the soil’s enzyme activity can potentially lessen the negative effects of the accumulated pollutants and improve the soil’s overall health and quality. Soil enzymes are biologically active components that have a catalytic impact and are released from root exudates, crop residues, and animal remains. The activity of enzymes serves as an excellent bioindicator of soil cleanliness and quality because they are sensitive to heavy metals. X-ray diffraction (XRD) was used to quantify the mineral elements in soil using 40 kV parallel beam optics, 30 mA, and CuKα radiation. Meanwhile, the activity of the enzyme was essayed in different coupled substrates. Thirteen (13) clay minerals were found, including Talc 2M, Kaolinite 2M, and Chlorite Lawsonite Muscovite 2M1. The detected trace elements have high concentration levels that exceed the World Health Organization’s (WHO) allowed levels. The identified elements affected the enzyme activity at different levels. The Mn, Al, Si, V, Ti, and Ca negatively affect soil enzyme activity, specifically invertase (INV). However, the amount of Mg, K, Fe, and Zn showed a slightly positive effect on the same enzyme (INV). According to this view, these elements come from several sources, each with a particular impact on soil contamination and enzyme activity. High levels of heavy metals in this study may be due to improper waste disposal, limited recycling opportunities, lack of public awareness, and inadequate enforcement of waste management regulations. It is essential to employ Fourth Industrial Revolution (4IR) technologies, correct disposal techniques, suitable agricultural methods, preventive regulations, and efficient waste management to mitigate the negative effects of heavy metals on the environment.
]]>Waste doi: 10.3390/waste2010004
Authors: Nobuki Morita Yo Toma Hideto Ueno
The disposal of tea leaves discarded in the tea beverage market and clinker from coal-fired power plants has an impact on the environment; however, there are no reported cases of their combination for composting. Therefore, this study evaluated the effect of adding clinker from a coal-fired power plant to compost based on tea leaves, an organic waste product, on the composting rate and quality. The tea leaves-only compost was designated as Clinker 0%, and composts with 20% (w/w), 40% (w/w), and 60% (w/w) tea leaves supplemented with clinker were designated as Clinker 20, 40, and 60%, respectively. Each mixed material was placed in a 35 L polypropylene container with a lid and allowed to compost for 95 days. The composting rate was evaluated by the chemical oxygen demand (COD) in hot water extract and plant tests using juvenile komatsuna (Brassica rapa var. perviridis). The addition of clinker reduced the COD at the beginning of composting by 52.0, 74.3, and 86.7% in Clinker 20, 40, and 60%, respectively, compared to Clinker 0%. Furthermore, root elongation one month after composting was inhibited by Clinker 0% (60.1% relative to distilled water), but not by the addition of clinker (91.7–102.7% relative to distilled water). This suggests that the addition of clinker to tea leaf compost may accelerate composting.
]]>Waste doi: 10.3390/waste2010003
Authors: Tafannum Torsha Catherine N. Mulligan
Food waste has emerged as a pressing concern, and thus advanced techniques to valorize food waste into nutrition rich materials as well as renewable energy are highly important. The exceptional biodegradability of food waste renders it a highly suitable substrate for anaerobic treatment. This leads to energy production and a reduction in the carbon footprint. Nevertheless, in frigid territories like Canada, the conventional mesophilic anaerobic digestion at 30–40 °C can require substantial amounts of energy. Consequently, this study introduces a new approach to treat food waste at psychrophilic temperatures (1–20 °C). Lower temperatures can negatively impact cellular processes during anaerobic treatment, rendering substrates less accessible to microscopic organisms. To address this challenge associated with lower temperatures, the study introduces an innovative biogas recirculation strategy. The primary objectives of this study are to assess the viability of anaerobic treatment for food waste at psychrophilic temperatures and to investigate the effectiveness of reintroduction of the produced biogas to the anaerobic system in enhancing biomethane generation and stability of the system. Batch experiments were conducted on food waste in various assessments, both with and without biogas recirculation. The outcomes revealed a methane concentration ranging from 68% to 93% when biogas recirculation was employed, whereas without this technique, methane concentration varied between 10% and 45%. Moreover, with biogas recirculation, the reduction in volatile solids reached a maximum of 92%, and there was an 82% decrease in chemical oxygen demand. In conclusion, the utilization of the recirculation of biogas at the psychrophilic temperature range enhanced biomethane production and reduction of volatile solids and chemical oxygen demand. This study underscores the potential of employing anaerobic treatment with reintroduction of produced biogas into the system in cold regions as an economically viable and sustainable choice for treating food waste with nominal energy consumption.
]]>Waste doi: 10.3390/waste2010002
Authors: Foteini Sakaveli Maria Petala Vasilios Tsiridis Efthymios Darakas
Traditionally, anaerobic digestion has been applied to mixed sludge, combining primary sludge (PS) with secondary sludge. However, recent research has unveiled the advantages of dedicated PS digestion due to its higher energy content. Anaerobic digestion (AD) of primary sewage sludge can offer a sustainable solution for managing sewage sludge while generating renewable energy. The present study provides a comprehensive examination of the current state of knowledge regarding the anaerobic digestion of PS. Co-digestion of PS with organic substrates, including food waste and agro-industrial residues, emerges as a promising approach to boost biogas production. Additionally, the utilization of additives such as glucose and clay minerals has shown potential in improving methane yield. Critical factors affecting AD, such as pretreatment methods, carbon-to-nitrogen (C/N) ratio, temperature, pH, volatile fatty acids (VFAs) levels, organic loading rates (OLR), inoculum-to-substrate ratio (ISR), and the role of additives, have been meticulously studied. Finally, this review consolidates existing knowledge to advance our understanding of primary sewage sludge anaerobic digestion, fostering more efficient and sustainable practices in sludge management and renewable energy generation.
]]>Waste doi: 10.3390/waste2010001
Authors: Ioannis Makrygiannis Vassilis Athanasiadis Theodoros Chatzimitakos Martha Mantiniotou Eleni Bozinou Stavros I. Lalas
Stone fruits, such as the apricot (Prunus armeniaca L.), are frequently consumed. As such, a substantial volume of apricot waste is generated at each stage of the food supply chain, including harvesting, processing, packaging, warehousing, transportation, retailing, and eventual consumption. This generates tons of waste annually on a global scale. The significant amounts of phenolics present in these wastes are primarily responsible for their antioxidant capacity and the subsequent health advantages they provide. As such, apricot pulp by-products could be a valuable reservoir of bioactive compounds, such as tocopherols, polyphenolic compounds, proteins, dietary fibers, etc. Moreover, apricot kernels are also recognized for their abundance of bioactive compounds, including polyphenols and tocopherols, which find utility in diverse sectors including cosmetology and the food industry. Both conventional and green methods are employed, and generally, green methods lead to higher extraction efficiency. The antimicrobial properties of apricot kernel essential oil have been widely recognized, leading to its extensive historical usage in the treatment of diverse ailments. In addition, apricot kernel oil possesses the capacity to serve as a viable resource for renewable fuels and chemicals. This review examines the potential of apricot waste as a source of bioactive compounds, as well as its utilization in diverse applications, with an emphasis on its contribution to health improvement.
]]>Waste doi: 10.3390/waste1040057
Authors: Saliha Keita Srecko Stopic Ferdinand Kiessling Tatjana Volkov Husovic Elif Emil Kaya Slavko Smiljanic Bernd Friedrich
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.
]]>Waste doi: 10.3390/waste1040056
Authors: Despoina Vlachoudi Theodoros Chatzimitakos Vassilis Athanasiadis Eleni Bozinou Stavros I. Lalas
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.
]]>Waste doi: 10.3390/waste1040055
Authors: Ronei de Almeida Claudinei de Souza Guimarães
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.
]]>Waste doi: 10.3390/waste1040054
Authors: Robert Haigh
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.
]]>Waste doi: 10.3390/waste1040053
Authors: Ben Joseph Heinz Stichnothe
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.
]]>Waste doi: 10.3390/waste1040052
Authors: Konstantin Schinkel Bastian Küppers Sven Reichenbach Teresa Rohrmeier Kajetan Müller Tanja Fell Sven Sängerlaub
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.
]]>Waste doi: 10.3390/waste1040051
Authors: Rikke Lybæk Tyge Kjær
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.
]]>Waste doi: 10.3390/waste1040050
Authors: Alae Lamtai Said Elkoun Mathieu Robert Frej Mighri Carl Diez
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).
]]>Waste doi: 10.3390/waste1040049
Authors: Adama Ndao Kokou Adjallé
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.
]]>Waste doi: 10.3390/waste1030048
Authors: Pranshoo Solanki Bhupesh Jain Xi Hu Gaurav Sancheti
This study systematically examined dredged materials from various aspects, including their sources, the volume generated annually, beneficial uses, and the management processes currently practiced. In addition, this paper presents the relevant policies governing the dredging, reuse, and disposal of dredged materials in the United States. A summary of various sources, types/classifications, and the physical and chemical properties of dredged materials used by various researchers are presented. This paper also summarizes the innovative techniques for the beneficial reuse of dredged materials in a wide range of applications in concrete materials, construction products, roadway construction, habitat building, landfill liner/cap, agriculture soil reconstruction, and beach nourishment. Further, limitations and corresponding solutions related to the beneficial use and management of dredged materials were provided in the end.
]]>Waste doi: 10.3390/waste1030047
Authors: Ana L. Izábal-Carvajal Leonardo Sepúlveda Mónica L. Chávez-González Cristian Torres-León Cristóbal N. Aguilar Juan A. Ascacio-Valdés
This study investigated the recovery of polyphenolic compounds such as punicalagin, punicalin, and ellagic acid via solid-state fermentation (SSF)-assisted extraction from pomegranate peel (Punica granatum L.) using Aspergillus niger GH1 and Saccharomhyces cerevisiae. Food processing has contributed to the increase in agroindustrial wastes, which has become a global concern due to environmental protection. However, these wastes can be valorized via the extraction of high-value components such as bioactive compounds. Ellagitannins extracted during the bioprocesses were identified via the HPLC–MS technique and quantified via total polyphenols (hydrolyzable and condensed assays). Enzymatic activities were tested. HPLC–MS analysis showed a decrease in the levels of punicalagin, the formation of punicaline, and the accumulation of ellagic acid during fermentation kinetics. The present study compares two different bioprocesses in order to obtain, from agroindustrial wastes, high-added-value compounds using SSF-.
]]>Waste doi: 10.3390/waste1030046
Authors: Zarifeh Raji Ahasanul Karim Antoine Karam Seddik Khalloufi
Heavy metal contamination in wastewater is a significant concern for human health and the environment, prompting increased efforts to develop efficient and sustainable removal methods. Despite significant efforts in the last few decades, further research initiatives remain vital to comprehensively address the long-term performance and practical scalability of various adsorption methods and adsorbents for heavy metal remediation. This article aims to provide an overview of the mechanisms, kinetics, and applications of diverse adsorbents in remediating heavy metal-contaminated effluents. Physical and chemical processes, including ion exchange, complexation, electrostatic attraction, and surface precipitation, play essential roles in heavy metal adsorption. The kinetics of adsorption, influenced by factors such as contact time, temperature, and concentration, directly impact the rate and effectiveness of metal removal. This review presents an exhaustive analysis of the various adsorbents, categorized as activated carbon, biological adsorbents, agricultural waste-based materials, and nanomaterials, which possess distinct advantages and disadvantages that are linked to their surface area, porosity, surface chemistry, and metal ion concentration. To overcome challenges posed by heavy metal contamination, additional research is necessary to optimize adsorbent performance, explore novel materials, and devise cost-effective and sustainable solutions. This comprehensive overview of adsorption mechanisms, kinetics, and diverse adsorbents lays the foundation for further research and innovation in designing optimized adsorption systems and discovering new materials for sustainable heavy metal remediation in wastewater.
]]>Waste doi: 10.3390/waste1030045
Authors: Dimitris Kalompatsios Vassilis Athanasiadis Theodoros Chatzimitakos Dimitrios Palaiogiannis Stavros I. Lalas Dimitris P. Makris
The current project aimed at examining the effect of the enrichment of commercial seed oils with waste orange peel (WOP) extracts on their polyphenolic profiles and resistance against oxidation. Polyphenol-containing WOP extracts were produced using a novel combination of ethanol and triacetin, and they were incorporated into seed oils (sunflower, soybean, corn oil), at a level of 36.87 mg per kg of oil. The oils were then stored at 60 °C, for 58 days. By performing a Rancimat test, it was shown that enrichment of sunflower, soybean, and corn oils with WOP extracts did not provoke any prooxidant effects, but, to the contrary, exerted an antioxidant action, with protection factors varying from 1.01 to 1.61. Furthermore, in all cases examined, it was demonstrated that, during the storage period, the stabilizing effect of WOP extract against oxidation was comparable to that observed in oil samples containing 200 mg BHT per kg oil. This outcome was ascertained by measuring the onset of peroxide value, thiobarbituric-acid-reactive substances, and the TOTOX value. Furthermore, it was revealed that the Trolox-equivalent antiradical activity of the enriched oils exhibited a decline at the end of the examination period, a fact most probably attributed to the depletion of the antioxidants occurring in the oils. It was concluded that the method proposed might be a means of stabilizing commercial seed oils against oxidation, and of enhancing their nutritional value by enriching them with natural polyphenols.
]]>Waste doi: 10.3390/waste1030044
Authors: Duncan Cree Stephen Owuamanam Majid Soleimani
An option to reduce the exploitation and depletion of natural mineral resources is to repurpose current waste materials. Fillers are often added to polymers to improve the properties and lower the overall cost of the final product. Very few studies have assessed the use of waste brown eggshell powder (BESP) as filler in polylactic acid (PLA). The addition of mineral fillers in a polymer matrix can play an important role in the performance of a composite under load. Therefore, tailoring the amount of filler content can be a deciding factor as to which filler amount is best. The goal of this study was to investigate the effect of brown eggshells compared to conventional limestone (LS) powder on the mechanical properties of PLA composites. One-way analysis of variance (ANOVA) was used to carry out the statistical analysis on the average values of each composite mechanical property tested. Scanning electron microscopy (SEM) was used to view if there were any differences in the fractured surfaces. Overall, the LS performed marginally better than the BESP fillers. The highest ultimate tensile and ultimate flexural strengths for eggshell composites containing 32 µm fillers had values of 48 MPa (5–10 wt.% BESP) and 67 MPa (10 wt.%. BESP), respectively. Both the tensile and flexural modulus improved with filler contents and were highest at 20 wt.% with values of 4.5 GPa and 3.4 GPa, respectively. The Charpy impact strength decreased for all filler amounts. SEM micrographs identified changes in the fractured surfaces due to the additions of the filler materials. The ANOVA results showed statistically significant differences for the composite materials. After five weeks of soaking in distilled water, the composites containing 20 wt.% BESP fillers had the highest weight gain. The study demonstrated that waste brown eggshells in powdered form can be used as a filler in PLA composites.
]]>Waste doi: 10.3390/waste1030043
Authors: Eduardo J. P. Martin Deborah S. B. L. Oliveira Luiza S. B. L. Oliveira Barbara S. Bezerra
The improper disposal of PET bottle waste in Brazil jeopardizes the sustainability goals, impacting the social, economic, and environmental aspects. In order to tackle this issue, this study introduces a framework that was developed using a combination of environmental and social life cycle assessments (LCAs), along with a modified Analytic Hierarchy Process (AHP) methodology. Nine disposal scenarios were evaluated in Bauru, Brazil, including various combinations of landfills, sorting cooperatives, and incineration. Environmental (Env-LCA) and social (S-LCA) assessments followed the ISO 14040 standards, with the S-LCA incorporating the UNEP/SETAC guidelines. Scenario 9 was identified as the most sustainable option from the evaluated scenarios, with 100% of the waste sent to sorting cooperatives, with modified collection schemes. Conversely, Scenario 1, with a high landfill percentage, proved to be the least sustainable.
]]>Waste doi: 10.3390/waste1030042
Authors: Paul W. Baker Adam Charlton
Valorisation of wheat bran can be achieved by solid state fermentation (SSF), through application of this material as a growth substrate for a natural white rot fungal isolate, Trametes versicolor CM13, to produce lignin-degrading enzymes. One of the main challenges in optimising and upscaling (SSF) processes is the accurate adjustment and maintenance of moisture conditions. This factor was assessed in the scale up of microcosms and was evaluated over 28 days, under two slightly different moisture contents, reflecting minor differences in experimental conditions during set up and operation of the SSF process. In addition, the microcosms were processed differently from the initial trial using homogenisation of whole microcosms to create a homogeneous mixture prior to sampling. This appeared to result in less variation among the collected samples from the microcosms. Variation of measured parameters as a percentage of actual values measured ranged from 1.33% to 144% in the unmixed microcosms and from 0.77% to 36.0% in the pre-mixed microcosms. Decomposition in the more saturated microcosms progressed more quickly as hemicellulose content decreased and reached a steady state after 14 days, whereas hemicellulose content continued to decrease until 21 days in the less saturated microcosms. Lignin-degrading enzyme activities were not significantly different between either sets of experiments except for laccase on day 7. Laccase and manganese peroxidase activities were highest on day 21 and were similar in both sets of experiments. Enzyme activities on day 21 in the microcosms at moisture content of 42.9% and at 54.6% for laccase activities were 750 ± 30.5 and 820 ± 30.8 units, and for manganese peroxidase, activities were 23.3 ± 6.45 and 21.4 ± 21.4 units, respectively. These results revealed different decomposition rates during the early stage of solid-state fermentation as a function of the initial moisture content, whereas final enzyme activities and fibre content during the later stage were similar in microcosms having different moisture contents at the start.
]]>Waste doi: 10.3390/waste1030041
Authors: Yuxiang Yao Chandhini Ramu Allison Procher Jennifer Littlejohns Josephine M. Hill James W. Butler
The amount of municipal solid waste (MSW) generation in Canada was 34 million tonnes in 2018. Responsible waste management is challenging, but essential to protect the environment and to prevent the contamination of the ecosystem on which we rely. Landfilling is the least desirable option, and diversion through thermo-chemical conversion to value-added products is a good option for difficult-to-recycle waste. In this study, the amounts, moisture contents, heating values, and compositions of municipally collected solid waste produced in Canada are reported, a classification that is suitable for conversion purposes is proposed, and the potential for thermo-chemical conversion is determined. Much of the waste generated in Canada is suitable for being converted, and its potential for heat or electricity generation was determined to be 193 PJ/yr and 37 TWh/y, respectively. The GHG emissions that are saved through diversion from the landfill, while assuming the generated heat or electricity offsets natural gas combustion, gives a GHG reduction of 10.6 MMTCO2E/yr or 1.6% of Canada’s GHG emissions. The blending of waste in feedstocks can have varying effects on the amount of biogenic CO2 produced per unit energy in the feedstock, which is an important consideration for new projects. Other considerations include the heating values, moisture contents, and contaminant levels in the waste.
]]>Waste doi: 10.3390/waste1030040
Authors: Guilherme Peixoto Gustavo Mockaitis Wojtyla Kmiecik Moreira Daniel Moureira Fontes Lima Marisa Aparecida de Lima Filipe Vasconcelos Ferreira Lucas Tadeu Fuess Igor Polikarpov Marcelo Zaiat
Second-generation (2G) ethanol production has been increasingly evaluated, and the use of sugarcane bagasse as feedstock has enabled the integration of this process with first-generation (1G) ethanol production from sugarcane. The pretreatment of bagasse generates pentose liquor as a by-product, which can be anaerobically processed to recover energy and value-added chemicals. The potential to produce biohydrogen and organic acids from pentose liquor was assessed using a mesophilic (25 °C) upflow anaerobic packed-bed bioreactor in this study. An average organic loading rate of 11.1 g COD·L−1·d−1 was applied in the reactor, resulting in a low biohydrogen production rate of 120 mL·L−1 d−1. Meanwhile, high lactate (38.6 g·d−1), acetate (31.4 g·d−1), propionate (50.1 g·d−1), and butyrate (50.3 g·d−1) production rates were concomitantly obtained. Preliminary analyses indicated that the full-scale application of this anaerobic acidogenic technology for hydrogen production in a medium-sized 2G ethanol distillery would have the potential to completely fuel 56 hydrogen-powered vehicles per day. An increase of 24.3% was estimated over the economic potential by means of chemical production, whereas an 8.1% increase was calculated if organic acids were converted into methane for cogeneration (806.73 MWh). In addition, 62.7 and 74.7% of excess organic matter from the 2G ethanol waste stream could be removed with the extraction of organic acid as chemical commodities or their utilization as a substrate for biomethane generation, respectively.
]]>Waste doi: 10.3390/waste1030039
Authors: Essossinam Beguedou Satyanarayana Narra Komi Agboka Damgou Mani Kongnine Ekua Afrakoma Armoo
Waste and resource management in Togo is expected to become more difficult due to increasing socioeconomic development, industrialization, and renewable energy investments. Although there are numerous elements that affect waste and resource management, legislation and policy frameworks are essential. In response to the growing demands for environmental protection, the legal provisions and regulatory frameworks of waste and resource management, as well as the legal implementation process, must be more and more comprehensive. Some actions have been taken in Togo to improve the incorporation of more sustainable industrial processes, which include restrictions and regulations on MSW generation, decentralization of MSW management, policies and incentive systems that promote waste reduction, reuse, and recycling, improvement of enforcement through investigation and treatment of violations, and encouragement of macro-socio-economies in the management of municipal solid waste. In spite of the presence of these policies, the sector is still plagued with numerous challenges, mostly in terms of implementation and the application of these policies to develop tailor made and locally feasible solutions. This research paper highlights relevant policies relating to MSW management in Togo as well as key international conventions and policies. It also discusses the contribution that “transition management” can make to such processes, emphasizes the role of governance for sustainable development, and it suggests solutions with a long-term transformation impact such as the incorporation of waste to energy systems into industrial processes. The paper further identifies some flaws and challenges with law implementation on MSW management and suggests solutions to improve the effectiveness of law implementation and the conditions and criteria for a safe and secure way to use waste-derived materials and fuels or by-products coming from society or other industries. These policy suggestions may also be applicable globally at an individual industry level to encourage the creation of more Green Industrial Companies (GICs).
]]>Waste doi: 10.3390/waste1030038
Authors: Nikita Zatyko Savindi Caldera Cheryl Desha
Every year in Australia, the household, commercial and industry sectors generate more than five million tonnes of food waste, with the majority of it ending up in landfills that are costly to run and diminishing in availability. There are urgent calls for effective waste management practices to better address the challenges related to increasing volumes of food waste. This study evaluates potential food waste collection and composting initiatives that will ensure the implementation of the appropriate policies and technologies, and best practice of utilizing food waste as a natural resource. A series of semi-structured interviews were conducted with practitioners from the Southeast Queensland waste industry to gain insights on the challenges and opportunities for implementing a Food Organics, Garden Organics (FOGO) system. The interviews revealed five key themes: levies and taxes, capital investment challenges, lack of capacity, contract inefficiencies, and separate waste streams. Organisations and companies in the waste industry heavily rely on funding in order to technologically advance. There is a divergence of attention between technology and policy. Advancement of technology grows faster than the policies that regulate the appropriate use and level of effectiveness of the introduced technology. Both policy and technological changes need to occur simultaneously for Queensland to evolve and develop a social-economic system that favours a non-wasteful and sustainable future.
]]>Waste doi: 10.3390/waste1030037
Authors: Paolina Scarponi Marco Bravi Cristina Cavinato
The winery sector represents one of the most important agricultural industries in Mediterranean country. Wine production processes generate a large amount of wastes and wastewaters that must be treated before their release in the environment. Among these wastes, wine lees, defined as the viscous material that settles on the bottom of fermenters, represent about 13% of the total wine production. The wine lees do not have applications within a circular economy approach, due to their low value; ethanol and tartaric acid are the only compounds recovered, while the rest is usually not valorized. The aim of this study is to explore the possible cultivation of microalgae on a liquid fraction of wine lees in a batch test at different substrate/inoculum dilutions. The results highlighted that Chlorella vulgaris can grow on wine lees at 1:10 and 1:5 dilutions, but a spontaneous yeast-microalgae consortium is observed (biomass production of 2 g l−1). A high lipid and protein storage was detected in the yeast-microalgae consortium (34.56 ± 13.70% and 39.73 ± 4.49%, respectively), associated with a high sCOD and polyphenols removal (99.95 ± 0.01% and 92.31 ± 0.02%, respectively), encouraging biological wine lees treatment.
]]>Waste doi: 10.3390/waste1030036
Authors: Salifou Ndam Alirou Fit Touikoue Jérôme Chenal Jean-Claude Baraka Munyaka Armel Kemajou Abdou Kouomoun
More and more cities in Southern Africa are struggling to manage their waste in a context of rapid urbanisation and increasing poverty. In the Cameroon’s largest city, Yaoundé, managing household waste is a growing concern. The public and the authorities cast blame on each other, and the actions taken by each party far from guarantee an efficient management of household waste, which litters the streets. Considering the above, this paper analyses the socio-political practices of stakeholders and their influence on household waste management in Yaoundé. Based on a qualitative survey that combined both a literature review and interviews, the research analysed the challenges related to household waste management with regard to the economy, the environment, and public health. In addition, a cartographic survey using KoboToolbox was conducted in all seven municipalities to analyse the geographical distribution of the waste areas, their size, and their status within the city organizational framework. In total, 264 waste dumps were collected, of which 110 were formal waste using a waste bin of varying size. Social constructivism, stakeholder theory, and strategic analysis were mobilized to analyse the urban waste governance in Yaoundé. Thus, the poor quality of household waste management in Yaoundé was explained using political, economic, sociocultural, and environmental parameters. The social practices and dynamics of the stakeholders generate undesirable consequences that hinder the achievement of the Sustainable Development Goals (SDGs). By combining social science and engineering methods, this research aims to demonstrate that the shortcomings of waste governance in Yaoundé are both a collective (authorities/public powers) and individual (citizens) matter.
]]>Waste doi: 10.3390/waste1030035
Authors: Modeste Kameni Nematchoua José A. Orosa
Nowadays, the methodology aiming to achieve carbon neutrality and net zero energy on a large scale is known. Despite this, few specialists are mastering this technology globally. What new scenarios. applied at the neighbourhood scale. generate a significant reduction in the rate of CO2 emissions and energy demand? In addition, a lack of massive, regular, and consistent data on carbon emissions and energy consumption has made it significantly difficult to understand the origins of climate change at the building and neighbourhood scales. This work has, as its main goal, the assessment of different strategies that facilitate reduction in the concentration of CO2 and lower energy demands at the district level. The life cycle assessment of a new district has been carried out over 100 years during the four stages of the life cycle of the neighbourhood (construction, operation, demolition and end of life). The results showed that up to 93% of greenhouse gas (GHG) was produced during the operational stage. The energy demand due to transport and waste management represented 60% of the total energy demand of the district during the operational stage. There is still a possibility to maintain air temperature growth around 1.5 °C in the next decade by means of the following: Global warming + 100% of heavy renovation of all buildings + 100% of electric car − renewable energy. This strategy would facilitate a reduction of over 92% of the CO2 produced at the district level.
]]>Waste doi: 10.3390/waste1020034
Authors: Kuok Ho Daniel Tang
Plastic pollution has received unprecedented attention globally, and there are increasing calls to control it. Despite this, the uptrends of plastic consumption and mismanaged plastic waste show little sign of reversal. This review aims to examine the attitudes of various societal groups towards plastics to identify the behavioral barriers to reduce plastic pollution and synthesize effective countermeasures. It achieved the aim through content analysis of the most recent literature related to attitudes and behaviors towards plastic pollution, consumption and management, as well as an important emerging theme on plastics recycling ecosystem and economy. It reveals the general negative attitudes of the participants in the studies reviewed towards plastic pollution and their willing attitude to act against it by supporting campaigns, paying for environmentally friendly alternatives and supporting solution-based interventions from governments including policies, regulations and guidelines. Inconvenience due to limited options for plastic items and habits are two main barriers to behavioral changes. This underscores the crucial roles of governments to tap into these attitudes to lead and intensify plastic pollution control through a multi-pronged approach that facilitates systematic substitution of conventional plastics with environmentally friendly alternatives as well as the stepping-up of the circular plastic economy and industrial symbiosis. This review deems that progressively regulated capping of conventional plastic production and consumption could help the transition, and the public could complement government endeavors through education, mutual influence and awareness-raising which could also be driven by governmental policies and programs.
]]>Waste doi: 10.3390/waste1020033
Authors: Veronica D’Eusanio Lucia Bertacchini Andrea Marchetti Mattia Mariani Stefano Pastorelli Michele Silvestri Lorenzo Tassi
Apricot (AS), peach (PS), and plum shells (PlS) were examined as sustainable aggregates for non-structural lightweight concrete. The extraction of natural resources has a significant environmental impact and is not in line with the Sustainable Development Goals (SDGs) of Agenda 2030. Recycling agri-food waste, such as fruit shells, fully respects circular economy principles and SDGs. The chemical and physical properties of the shells were investigated using scanning electron microscopy (SEM) for microstructure analysis and TG-MS-EGA for thermal stress behavior. Two binding mixtures were used to prepare the concrete samples, one containing lime only (mixture “a”) and one containing both lime and cement (mixture “b”). Lime is a more sustainable building material but it compromises mechanical strength and durability. The performance of lightweight concrete was determined based on the type of aggregate used. PS had a high-water absorption capacity due to numerous micropores, resulting in lower density (1000–1200 kg/m3), compressive strength (1–4 MPa), and thermal conductivity (0.15–0.20 W/mK) of PS concrete. AS concrete showed the opposite trend (1120–1260 kg/m3; 2.8–7.0 MPa; 0.2–0.4 W/mK) due to AS microporosity-free and denser structure. PlS has intermediate characteristics in terms of porosity, density, and water absorption, resulting in concrete with intermediate characteristics (1050–1240 kg/m3; 1.9–5.2 MPa; 0.15–0.3 W/mK).
]]>Waste doi: 10.3390/waste1020032
Authors: Ioannis Varvaringos Eva Skourtanioti Georgios Letsos Evgenia Rizoudi Ektoras Makras Margarita Panagiotopoulou Sofia Papadaki Katerina Valta
Sustainable bioeconomy is a promising pathway towards the transition to a circular and climate-neutral economy. The valorization of biowaste is a key player in this direction. This paper presents the design and development of the AgriPLaCE Platform, which aims to promote synergies that enable the utilization of biowaste from the fruit and vegetable supply chain. The platform consists of the AgriPLaCE Waste Management Database, which provides users with an extended list of potential utilization methods for various types of fruit and vegetable biowaste streams, and the AgriPLaCE Synergies Tool, which facilitates synergies between different actors involved in the biowaste-to-resource value chain from agricultural waste production to waste treatment and new valuable products’ exploitation. Initially, the conceptual design of both tools took place based on analysis of user needs and services alongside the system architecture. Following this, the AgriPLaCE Platform was developed with the implementation of all the necessary subsystems. The results of the platform’s implementation demonstrated its potential to generate multiple collaborations and synergies while users can also deepen their knowledge about alternative and emerging treatment technologies and valuable products from a wide range of fruit and vegetable biowaste streams.
]]>Waste doi: 10.3390/waste1020031
Authors: Sergey M. Frolov Anton S. Silantiev Ilias A. Sadykov Viktor A. Smetanyuk Fedor S. Frolov Jaroslav K. Hasiak Alexey B. Vorob’ev Alexey V. Inozemtsev Jaroslav O. Inozemtsev
Reported in the article is further progress in the development of the novel pulsed detonation gun (PDG) technology for the conversion of organic wastes into syngas in a two-component gasifying agent (GA) containing ultra-superheated steam and carbon dioxide obtained by pulsed detonations of a natural gas–oxygen mixture at a frequency of 1 Hz. Experimental studies were carried out on a waste converter with a 40 dm3 flow reactor and two PDGs with a total volume of 2.4 or 3.2 dm3, which is approximately a factor of 6 and 4.5 less than in previous studies, respectively. The objective of the research was to find the design and operation parameters of the waste converter that provide a minimum amount of CO2 in the gasification products. Waste machine oil was used as a feedstock. It is shown that, compared with the earlier experiments with a higher average temperature of the reactor wall and with a PDG of a much larger volume, the contents of H2, CO, CH4, and CO2 in the syngas remained virtually unchanged, whereas the efficiency of the gasification process increased significantly: the use of 1 g of natural gas made it possible to gasify up to 4 g of the feedstock. It is also shown that the determining role in the gasification process of liquid feedstock is played by the feedstock residence time in the PDG rather than in the reactor. The minimum ratio between the flow rates of the GA and liquid feedstock, the minimum ratio between the flow rates of combustible gas and liquid feedstock, as well as the actual GA consumption in the gasification process are determined experimentally.
]]>Waste doi: 10.3390/waste1020030
Authors: Arthur Chevalier Philippe Evon Florian Monlau Virginie Vandenbossche Cecilia Sambusiti
This study aimed to evaluate the effects of mechanical treatment through twin-screw extrusion for the enhancement of biomethane production. Four lignocellulosic biomasses (i.e., sweetcorn by-products, whole triticale, corn stover and wheat straw) were evaluated, and two different shear stress screw profiles were tested. Chemical composition, particle size reduction, tapped density and cellulose crystallinity were assessed to show the effect of extrusion pretreatment on substrate physico-chemical properties and their biochemical methane production (BMP) capacities. Both mechanical pretreatments allowed an increase in the proportion of particles with a diameter size less than 1 mm (from 3.7% to 72.7%). The most restrictive profile also allowed a significant solubilization of water soluble coumpounds, from 5.5% to 13%. This high-shear extrusion also revealed a reduction in cellulose crystallinity for corn stover (i.e., 8.6% reduction). Sweetcorn by-products revealed the highest BMP values (338–345 NmL/gVS), followed by corn stover (264–286 NmL/gVS), wheat straw (247–270 NmL/gVS) and whole triticale (233–247 NmL/gVS). However, no statistical improvement in maximal BMP production was provided by twin-screw extrusion. Nevertheless, BMP kinetic analysis proved that both extrusion pretreatments were able to increase the specific rate constant (from 13% to 56% for soft extrusion and from 66% to 107% for the high-shear one).
]]>Waste doi: 10.3390/waste1020029
Authors: Magdalena Lech Oliwia Gala Karolina Helińska Katarzyna Kołodzińska Hanna Konczak Łukasz Mroczyński Eliza Siarka
Nowadays, electroplating plants are factories that use huge amounts of water in the coating process of anti-corrosion layers. They are required to decrease the heavy metal content to very low values before releasing the post-process water into the aquatic environment. They very often decrease their content using coagulation combined with flocculation. However, these processes are often not effective enough, and the concentration of a given metal does not reach a satisfactory low level. The use of membrane techniques to purify this type of wastewater leads to a reduction in the content of heavy metals, including nickel, to zero values. This allows for not only reducing the negative impact on the aquatic environment but also a step toward more conscious management of water resources—namely, the reuse of water in the electroplating process. The following review not only describes the membrane methods used to treat the wastewater considered, e.g., nanofiltration, ultrafiltration, or electrodialysis, but also shows the directions of development of these processes.
]]>Waste doi: 10.3390/waste1020028
Authors: Claudio Marciano
Waste management is one of the most strategic areas of regional policy planning. The impact of decisions such as the allocation of industrial waste treatment plants and waste collection strategies can affect the economic structure and quality of life of territories. The effectiveness of regulatory and organisational arrangements of Regional Waste Plans is linked to the availability of technologies and material infrastructure, but also to social consensus and behaviours. On this level, participatory planning conducted through foresight techniques plays an increasing role. The article presents an innovative case carried out in Valle d’Aosta in 2021, with the aim of promoting the participatory methodology experimented and the institutionalisation of such applications in strategic waste planning processes. The process involved 35 different stakeholders (unions, businesses, schools, trade, environmental associations, etc.) in structured consultations based on the principle of building a shared transition to 2030. In particular, the project was effective in broadening the participation of civil society in the area, in making the plan’s objectives more ambitious, and in fostering the creation of a collaborative network between public, market and third sector actors.
]]>Waste doi: 10.3390/waste1020027
Authors: Apichon Watcharenwong Kawintra Kongka Anusara Kaeokan Chanat Chokejaroenrat Chainarong Sakulthaew
Ethanol production wastewater contains high quantities of dark–brown pigments (melanoidin) that result in low color removal using conventional biological treatments. Advanced oxidation processes (AOPs) are the most documented methods for reducing the color associated with melanoidin. This study examines the degradation of melanoidin using AOPs based on photo–Fenton, sono–Fenton, and sono–photo–Fenton processes. Their effects on decolorization were investigated based on light intensity, ultrasonic frequency, and the iron concentration (Fe2+)–to–H2O2 ratio. This study showed that ultrasonic waves and UV light result in a higher melanoidin decolorization efficiency than Fenton reactions alone. The initial color values were reduced from 5000–5500 ADMI to below 500 ADMI for both processes because the ultrasonic waves and ultraviolet light induced H2O2 breakdown into the 🞄OH radical. Reducing the color of the melanoidin using the photo–Fenton process resulted in a decolorization rate of 0.1126 min−1, which was higher than the rates of both the sono–Fenton and sono–photo–Fenton processes. These results provide proof that the photo–assisted Fenton process is more applicable to treating dye–contaminated water than are other enhancing approaches.
]]>Waste doi: 10.3390/waste1020026
Authors: David D. J. Antia
In this study, a continuous flow of a synthetic, dry, and acidic waste synthesis gas (WSG) (containing N2, H2, CO, CH4, and CO2) at ambient temperatures was first passed through a fixed bed reactor (FBR) containing halite + m-Fe0 and then a saline bubble column diffusion reactor (BCDR) containing m-Fe0. The FBR converted 47.5% of the CO + CH4 + CO2 into n-C0. Passage of the n-C0 into the BCDR resulted in the formation of the desalination catalyst (Fe0:Fe(a,b,c)@C0) + CH4 + CO + CO2 + CxHy, where 64% of the feed n-C0 was converted to gaseous products. The desalination pellets can remove >60% of the water salinity without producing a reject brine or requiring an external energy source. The gaseous products from the BCDR included: CxHy (where x < 6), CO, CO2, and H2.
]]>Waste doi: 10.3390/waste1020025
Authors: Adam Lyndsell James M. Buick
In practical applications, waste water piping includes elbows and bends which give unrepeatable, asymmetric and swirling flow profiles, which result in flow meter inaccuracy. Flow conditioners can be inserted into the pipe network to remove these flow patterns prior to a flow meter, to improve the accuracy of the measurement and to reduce the length of straight-run which would otherwise be required. In this investigation, a new design of flow conditioner is considered in two configurations, with and without vanes. The performance of the conditioner is considered by exposing it to a swirling flow that was disturbed by two 90° bends. The flow downstream of the conditioner was simulated using CFD software STAR-CCM+ 12 to find the downstream axial velocity profile, swirl angle and pressure drop. The vane-less conditioner provided a suitable axial profile for flow measurement 2D downstream, at which point the swirl was removed. This illustrated the improved performance compared to other conditioners in the literature, but came at the price of a somewhat higher pressure drop. The addition of vanes improved the performance slightly in terms of regulating the flow and removing swirl, while at the same time increasing the pressure drop further.
]]>Waste doi: 10.3390/waste1020024
Authors: Muyiwa Lawrence Adedara Ridwan Taiwo Hans-Rudolf Bork
The annual volume of waste generated in sub-Saharan Africa (SSA) increased from 81 million tonnes to 174 million tonnes per year between 2012 and 2016 and is projected to reach 269 million tonnes in 2030. In 2018, SSA’s municipal solid waste (MSW) collection coverage was estimated at 44%. Concerned that the waste generation rate outweighs the collection pace, we conducted a systematic review of studies on MSW collection to examine the current situation in the region concerning the waste collection and coverage rates and to highlight the impediments to rapid progress in waste collection using the lens of four cities. Findings reveal that, despite the involvement of private waste collectors, collection and coverage rates are still below the desired 100% with backlogs of uncollected waste in public spaces, especially in low-income neighbourhoods where coverage remains abysmally low. This study fortifies the systematic discussion on MSW collection and coverage rates by conducting a meta-analysis. The result of the analysis shows that the waste collection and coverage rates are 65% and 67% in SSA, respectively. Aside from the paucity of data on waste generation rate and characterisation, most available data are incongruent. The review further shows that although several studies have been carried out on waste disposal, waste treatment and recycling in SSA studies directly focused on MSW collection are still few, leaving room for more research in this area. The review offers suggestions on how collection and coverage rates can be increased and equally proposes a strategy for reducing scavenging activities in the region’s unsanitary landfills, given its concomitant health impacts on the scavengers.
]]>Waste doi: 10.3390/waste1020023
Authors: Genevieve Soon Hui Zhang Adrian Wing-Keung Law Chun Yang
The formulation of the CFD-DEM model, CD-MELT, is established in this study to include three-phase non-isothermal processes with simultaneous combustion and melting for gasification simulations. To demonstrate the model capability, CD-MELT is used to assess the need for slag recycling for the non-isothermal melting of municipal solid wastes (MSW) in a prototype waste-to-energy research facility. The simulation encompasses the full fixed-bed slagging gasification process, including chemical reactions and melting of MSW and slag. In order to assess the need for slag recycling, comparisons are made for the two cases of with and without, in terms of the slag mass, liquid slag volume fraction, exit gas composition, and temperature distribution in the gasifier. The prediction results enable the tracking of liquid molten slag as it permeates through the solids-packed bed for the first time in the literature as far as we are aware, which is crucial to address design considerations such as distribution of bed temperature and optimal location for slag-tap holes at the bottom, as well as potential slag clogging within the porous media. The model also predicts an uneven and intermittent slag permeation through the packed bed without the recycling, and provides a plausible explanation for the operators’ experience of why slag recycling is important for process stability. Finally, the predicted slag outlet temperature using the proposed CFD approach also agrees well with the measurement data published in an earlier case study for the same facility.
]]>Waste doi: 10.3390/waste1020022
Authors: W. A. M. A. N. Illankoon Chiara Milanese Maria Cristina Collivignarelli Sabrina Sorlini
The quantity of organic waste generated by agricultural sectors is continually increasing due to population growth and rising food demand. Rice is the primary consumable food in Asia. However, many stakeholders follow a linear economic model such as the “take–make–waste” concept. This linear model leads to a substantial environmental burden and the destruction of valuable resources without gaining their actual value. Because these by-products can be converted into energy generating and storage materials, and into bio-based products by cascading transformation processes within the circular economy concept, waste should be considered a central material. This review examines the composition of rice straw, bran, and husks, and the procedures involved in manufacturing value-added goods, from these wastes. Moreover, starting with an extensive literature analysis on the rice value chains, this work systematizes and displays a variety of strategies for using these by-products. The future development of agricultural waste management is desirable to capitalize on the multi-functional product by circulating all the by-products in the economy. According to the analysis of relevant research, rice straw has considerable potential as a renewable energy source. However, there is a significant research gap in using rice bran as an energy storage material. Additionally, modified rice husk has increased its promise as an adsorbent in the bio-based water treatment industry. Furthermore, the case study of Sri Lanka revealed that developing countries have a huge potential to value these by-products in various sectors of the economy. Finally, this paper provides suggestions for researchers and policymakers to improve the current agriculture waste management system with the best option and integrated approach for economic sustainability and eco- and environmental solution, considering some case studies to develop sustainable waste management processes.
]]>Waste doi: 10.3390/waste1020021
Authors: Portia Adade Williams Satyanarayana Narra Edward Antwi Wilhemina Quaye Elizabeth Hagan Roland Asare Johnny Owusu-Arthur Vicky Shettigondahalli Ekanthalu
Issues of rising waste generation are calling for proper management and the sustainable control of waste. This study examines waste- and energy-relevant policies and strategies in Ghana and the stakeholders’ perceptions on such policies and strategies. It explores the gaps and challenges in national policy documents to guide the implementation of waste-to-energy projects in Ghana. The approach adopted includes a comprehensive review of relevant policy documents and key informant interviews with selected key stakeholders. Factors such as limited funding, inadequate logistics, expertise and infrastructure, growing population and negative attitudes of general public towards the environment, amongst others, are the concerns identified. Findings from the policy review revealed that capacity to harness energy from waste could be improved through appropriate technologies suitable for Ghana. Adequate institutional framework, stakeholders and mechanisms to explore opportunities to coordinate implementation of various policy strategies and interventions have been established. Streamlining strategies to constitute components to improve governance on waste management, improving financing to ensure sustainable investment in waste-to-energy projects, improving research on waste-to-energy technologies as well as enhancing public interest and education on proper waste management could enhance the implementation of national waste and energy policies for feasible up-scaling of waste-to-energy technologies in Ghana.
]]>Waste doi: 10.3390/waste1010020
Authors: Matthieu Jacob Bertrand Segues Marie-Claire Lot El hadji Ibrahima Ndiaye Cecilia Sambusiti Patrick Baldoni-Andrey Frédéric Perie
This paper presents the results obtained on an oil and gas field terminal in Gabon during a continuous 8-month long operation involving the move of a pre-industrial bed biofilm bioreactor pilot for treating highly saline produced water (100 g/L). After several months of efficient acclimation of the biofilm carriers, more than 90% of the biological oxygen demand, 50% of total organic carbon and 35% of the chemical oxygen demand were removed during 1 h of residence time at a maximum organic loading rate of 12 kgCOD.m−3.day−1, making it a highly promising solution for offshore produced water treatment. These values reached more than 95%, 80% and 60% of BOD, TOC and COD removal, respectively, for 12 h residence time. In addition to the significant removal efficiency of the pilot, it is also important to highlight the robustness of the process. The presence of an acclimated biofilm properly attached to the carriers strongly reduced biomass washing during anomalous phases in comparison to a conventional activated sludge configuration. This technology favorably follows the three key pillars for implementing offshore technologies: high removal performance, robustness and low footprint.
]]>Waste doi: 10.3390/waste1010019
Authors: Waste Editorial Office Waste Editorial Office
High-quality academic publishing is built on rigorous peer review [...]
]]>Waste doi: 10.3390/waste1010018
Authors: Pietro Romano Emanuele Melchiorre Francesco Vegliò
Printed circuit boards are considered a secondary source of raw materials, such as precious or base metals. One of the most promising solutions for recovering these metals is certainly hydrometallurgy. However, the leaching of different metals from PCBs is hindered by the presence of an organic fraction that lowers the extraction yields. One solution to this problem is a pyrolysis pre-treatment which removes the organic fraction and enhances it through conversion into syngas. A steady-state simulation model was developed using ASPEN PLUS to describe the thermodynamic behavior of PCB pyrolysis. The pyrolysis reactor was modeled as a combination of the Yields reactor and the Gibbs reactor. The model has been validated using various data present in the literature. The composition of the different products was estimated through the minimization of Gibbs’s free energy. A sensitivity analysis was performed to investigate the influence of different parameters on the conversion yield and the syngas quality produced. Thanks to the study, it was possible to describe and analyze the pyrolysis of PCBs without requiring numerous experimental tests. The results show how steam gasification appears to be the most efficient technology for the pre-treatment of PCBs within a hydrometallurgical process.
]]>Waste doi: 10.3390/waste1010017
Authors: D. M. N. S. Dissanayaka S. S. Udumann D. K. R. P. L. Dissanayake T. D. Nuwarapaksha Anjana J. Atapattu
As a result of the increase in agricultural production and environmental pollution, waste management and disposal are becoming vital. Proper treatments, such as converting abundant bio-mass wastes into beneficial materials, might mitigate the negative effects and convert waste into reusable resources. Aquatic weeds are a significant concern in the majority of water bodies. Their quick growth, rapid ecological adaptations, and lack of natural enemies make these plants invasive, problematic, and challenging to manage over time. Although there are many methods to manage aquatic weeds, composting has been identified as one of the easily adapted and eco-friendly methods for transferring nutrients to the cropping cycle. Their short life cycle, higher biomass yield, higher nutrient compositions, and allelopathic and phytoremediation properties confirm their suitability as raw materials for composting. Most aquatic ecosystems can be maintained in optimum conditions while facilitating maximum benefits for life by identifying and developing proper composting techniques. Studying the ecology and morphological features of aquatic weeds is essential for this purpose. This is an overview of identifying the potential of aquatic weeds as a source of composting, targeting sustainable plant nutrient management while managing weeds.
]]>Waste doi: 10.3390/waste1010016
Authors: Alistair F. Holdsworth Harry Eccles Clint A. Sharrad Kathryn George
Nuclear fuel is both the densest form of energy in its virgin state and, once used, one of the most hazardous materials known to humankind. Though commonly viewed as a waste—with over 300,000 tons stored worldwide and an additional 7–11,000 tons accumulating annually—spent nuclear fuel (SNF) represents a significant potential source of scarce, valuable strategic materials. Beyond the major (U and Pu) and minor (Np, Am, and Cm) actinides, which can be used to generate further energy, resources including the rare earth elements (Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, and Tb), platinum group metals, (Ru, Rh, Pd, and Ag), noble gases (He, Kr, and Xe), and a range of isotopes useful for medical and energy generation purposes are also produced during fission. One reason for the accumulation of so much SNF is the low uptake of SNF recycle (or reprocessing), primarily due to the high capital and operational costs alongside concerns regarding proliferation and wastes generated. This study will highlight the predominantly overlooked potential for the recovery of strategic materials from SNF, which may offset costs and facilitate advanced waste management techniques for minimised waste volumes, thus increasing the sustainability of the nuclear fuel cycle on the path towards Net Zero. Potential challenges in the implementation of this concept will also be identified.
]]>Waste doi: 10.3390/waste1010015
Authors: Guanfu Liu Helena Hagelin-Weaver Bruce Welt
Regenerative Robust Gasification promises to convert unsorted organic waste, including all plastic waste, into the fungible, primary feedstock chemical methanol. As the backbone of the C1 chemical industry, methanol has broad application in circular economy chemical synthesis. This paper summarizes traditional and newer approaches for producing methanol from synthesis gas. Approaches, methods, reaction mechanisms, catalyst systems, catalyst synthesis methods, reactor types, and many other aspects are summarized.
]]>Waste doi: 10.3390/waste1010014
Authors: Audrey Lallement Christine Peyrelasse Camille Lagnet Abdellatif Barakat Blandine Schraauwers Samuel Maunas Florian Monlau
Agricultural biogas plants are increasingly being used in Europe as an alternative source of energy. To optimize the sizing and operation of existing or future biogas plants, a better knowledge of different feedstocks is needed. Our aim is to characterize 132 common agricultural feedstocks in terms of their chemical composition (proteins, fibers, elemental analysis, etc.) and biochemical methane potential shared in five families: agro-industrial products, silage and energy crops, lignocellulosic biomass, manure, and slurries. Among the families investigated, manures and slurries exhibited the highest ash and protein contents (10.3–13.7% DM). High variabilities in C/N were observed among the various families (19.5% DM for slurries and 131.7% DM for lignocellulosic biomass). Methane potentials have been reported to range from 63 Nm3 CH4/t VS (green waste) to 551 Nm3 CH4/t VS (duck slurry), with a mean value of 284 Nm3 CH4/t VS. In terms of biodegradability, lower values of 52% and 57% were reported for lignocelluloses biomasses and manures, respectively, due to their high fiber content, especially lignin. By contrast, animal slurries, silage, and energy crops exhibited a higher biodegradability of 70%. This database will be useful for project owners during the pre-study phases and during the operation of future agricultural biogas plants.
]]>Waste doi: 10.3390/waste1010013
Authors: Tom Haeldermans Jeamichel Puente Torres Willem Vercruysse Robert Carleer Pieter Samyn Dries Vandamme Jan Yperman Ann Cuypers Kenny Vanreppelen Sonja Schreurs
Green roofs contribute to more sustainable cities, but current commercial substrates suffer from important limitations. If carefully selected, biochar could serve as a viable option for a more sustainable green roof substrate. We propose a protocol to select an optimal biochar for green roof substrate amendment. Coffee husks, medium-density fiberboard, palm date fronds, and a mixture of waste wood, tree bark, and olive stone kernels are selected as residues for biochar production to develop a selection protocol. The residues are pyrolyzed at 350, 450, 500, and 550 °C in a lab-scale reactor. A pyrolysis temperature of 450 °C is selected for upscaling and is based on biochar yield, pH, salinity, and elemental composition. From evaluating the biochar characteristics after upscaling, it can be concluded that the biochar’s carbonization degree is mainly controlled by pyrolysis temperature, while yield, pH, and salinity are more dependent on the biomass properties. Ultimately, our procedure evaluates the presence of important contaminants, the biochar’s water holding capacity, salinity, pH, and carbonization degree. To validate the developed protocol, plant coverage experiments on green roofs are performed, which are quantified using a novel digital image processing method, demonstrating its efficient use to facilitate future biochar selection in substrates.
]]>Waste doi: 10.3390/waste1010012
Authors: Jung Eun Park Sang Eun Lee Seokhwi Kim
The oyster shell is a valuable calcium resource; however, its application is limited by its high NaCl content. Therefore, to establish the use of oyster shells as a viable resource, conditional experiments were conducted to select optimum parameters for NaCl removal. For this purpose, we compared leaching methods with batch and sequential procedures, determined the volume of water used for washing, and evaluated the mixing speed. The batch system removed NaCl when washed for >24 h over a shell to water ratio of 1:5. Results from the batch experiments confirmed that washing twice can completely remove NaCl from the shells on a like-for-like basis. Additionally, the efficiency of washing was sequentially evaluated in terms of the number of washing cycles. Compared to batch experiments, continuous washing could remove NaCl in approximately 10 min at a shell to water ratio of 1:4. We found that regardless of the washing methods, the volume of water used for washing is key for enhancing NaCl removal. Consequently, increasing the volume of water used for washing coupled with a proper sorting of fine particles can help enhance the purity of calcium, which will enable the use of oyster shell as an alternate Ca-resource.
]]>Waste doi: 10.3390/waste1010011
Authors: Santa Margarida Santos Ana Carolina Assis Leandro Gomes Catarina Nobre Paulo Brito
This paper aims to briefly overview gasification technologies of biomass and heterogeneous wastes as a means for syngas production. For this purpose, an overview of the existing technologies, their main advantages, limitations, and costs, as well as commercial plants and projects (lower TRL) operating with these technologies and syngas applications is presented. The type of technology and operating parameters should be selected considering the quality of the syngas as it will dictate its end use. Syngas quality is determined by the combination of feedstock properties, type of technology and process operating conditions, and the scale of operation. For smaller projects with a capacity of up to 10 MWth, fixed-bed technologies have been a recurring choice, while fluidized bed reactors can have an installed capacity above 100 MWth and are, therefore, more suitable for medium- and large-scale projects. Fluidized bed gasification technology supports feedstock flexibility, has scale-up potential, and presents relatively low cost, making it a suitable solution and a frequent choice for heterogeneous waste gasification in medium- or large-scale projects. Commercializing waste gasification technology is already a reality. However, more efforts need to be made so that pilot and demonstration projects can overcome the technological and economic problems and move towards commercialization.
]]>Waste doi: 10.3390/waste1010010
Authors: Jan Tinz Tim de Ancos Holger Rohn
In view of the increasing amount of plastic waste due to a yearly rise in production volume, mechanical recycling of post-industrial waste offers a way to use the scarce resources on earth more efficiently in addition to reducing the global warming potential in the production of raw materials. Therefore, this study addresses the calculation of the product carbon footprint for sorted industrial waste according to the specifications of ISO 14067. The plastics acrylonitrile–butadiene–styrene copolymer (ABS), polyamide 6.6 with 30% glass fiber (PA66GF30), polycarbonate (PC) and polyoxymethylene (POM) were balanced in Umberto LCA+ using the Ecoinvent v3.8 and GaBi SP40 2020 databases and primary data collection from the recycling company Occhipinti. A cut-off approach was applied as an allocation method for evaluating the industrial waste so that the plastic for grinding was imported without burdens from the previous product system. The results show that for all plastics under study, one of the main drivers of the carbon footprint is plastic dust from the grinding process. This insight was used in sensitivity analyses to optimize the modelled processes for a more sustainable production. Improvement potentials were identified by using solar power and disposing of the plastic dust separately according to the type of plastic.
]]>Waste doi: 10.3390/waste1010009
Authors: Cosmin Vancea Giannin Mosoarca
This research presents a new solution to use bottle glass wastes together with aluminum hydroxide for porous alumina glass ceramics synthesis. The firing of the samples was conducted at three temperatures: 800, 1000 and 1200 °C. The effect of the bottle waste glass addition on the firing shrinkage, apparent density porosity, chemical stability and compression strength of the sintered samples was investigated. The dimensional stability of the samples, varying between 4.75–11.87% is positively affected by waste glass/alumina substitution ratio. Higher amounts of glass waste lead to higher apparent densities, up to 1.80 g/cm3 and lower apparent porosities, around 33.74%, depending on the heat treatment temperature. All the studied glass ceramics have very good chemical stability that increase with the glass waste/alumina ratio. The compression strength of the obtained samples, ranging between 4.72–24.20 N/mm2 is negatively affected by increasing the glass waste amount due to its brittle behavior. The obtained results suggest the viability of the proposed recycling alternative for bottle glass waste together with aluminum hydroxide as porous alumina glass ceramics.
]]>Waste doi: 10.3390/waste1010008
Authors: Ioannis Giovanoudis Vassilis Athanasiadis Theodoros Chatzimitakos Olga Gortzi George D. Nanos Stavros I. Lalas
The traditional extraction methods used to recover natural antioxidants from food industry wastes involve significant amounts of hazardous solvents. A viable alternative is the use of non-toxic surfactants to remove organic compounds from wastes at temperatures above the cloud point. Cloud point extraction has only recently begun to be used to recover high-value added compounds from food industry wastes. In the current work, a method for the isolation of high-value added components from liquid tomato wastewater using a cloud point extraction method was developed and optimized. Food-grade lecithin was examined for its potential to be used as a surfactant in the developed procedure. Moreover, parameters affecting the extraction (ionic strength, sample pH, temperature of extraction, and surfactant concentration) were examined and optimized. According to the results, the maximum recovery of carotenoids from the sample could be achieved with the developed procedure, by simply adjusting the pH to 3.5, adding 35.6% (w/v) sodium chloride, and setting the temperature at 45 °C. Moreover, the amount of lecithin used was examined. In order to extract the total amount of carotenoids from a sample, it was found that either three extractions with 1% lecithin are needed, or two extractions with 2% lecithin. In addition, the antioxidant activity of the extract was examined and it was found to scavenge 36.3% of DPPH free radicals. This percentage was 10% lower compared to the initial sample, which suggests that the extracted compounds retain their activity. Overall, the developed procedure can be used to recover carotenoids in a cost-efficient and easy way.
]]>Waste doi: 10.3390/waste1010007
Authors: Rasha Maal-Bared
Quantitative microbial risk assessments (QMRAs) present an opportunity to systematically assess risk to wastewater treatment plant (WWTP) workers and mitigate work-related infectious diseases. However, while QMRAs often explore the impacts of aeration or treatment mechanism, or the use of controls to mitigate risk (e.g., ventilation, personal protective equipment (PPE)), fewer studies address other variables, such as differing tasks across plants, time spent conducting these tasks or size of plant. QMRA approaches also vary substantially in their findings and recommendations. The objective of this paper is to provide a risk-based wastewater worker task characterization for urban, municipal and industrial WWTPs along with mitigation measures. Routine tasks fell into five categories in ascending order of exposure and risk, Type A being the lowest and Type E being the highest. Percentage of full-time equivalent time spent on each task category was estimated, along with amount of wastewater exposure (mL) and inhalation duration (h). Estimates differed between urban and municipal plants but were similar in industrial and municipal systems. Finally, a checklist was developed to identify potential mitigation measures and prioritize H&S solutions for eight inspected WWTPs. The present work provides practical information for job safety assessments, H&S policies and QMRA method refinement.
]]>Waste doi: 10.3390/waste1010006
Authors: Charalampos Pavlopoulos Konstantina Papadopoulou Minas Theocharis Petros Tsakiridis Pavlina Kousi Artin Hatzikioseyian Emmanouella Remoundaki Gerasimos Lyberatos
As installed photovoltaic panels (PVPs) approach their End of Life (EoL), the need for a sustainable recovery plan becomes imperative. This work aims to reuse silicon from EoL PVPs as a potential catalyst/photocatalyst for wastewater treatment. PVPs were pretreated thermally. The resulting mixture was separated into different fractions using a trommel screen. Recovered silicon flakes were cleaned with HΝO3 and HF in order to obtain pure Si, which was then etched through a single stage Ag-assisted Chemical Etching process and decorated with Ag/Cu. Photocatalytic reduction of Cr(VI) in the presence of 5 mM citric acid was carried out in a 600 mL batch reactor irradiated by a Xenon 150 W arc lamp as well as under dark conditions. It was found that, in the presence of 1.2 g/L of Si catalyst, Cr(VI) at an initial concentration of 15 mg/L can be reduced below the detection limit (>99%), even under dark conditions, in 30–180 min, depending on the pH of the solution and the citric acid concentration. Citric acid was proved to assist the reaction in three ways: lowering the pH, increasing the solubility of the precipitate, preventing inhibition, and as sacrificial agent in photocatalysis. Irradiation, however, was shown to possibly inhibit the process if the citric acid concentration is low.
]]>Waste doi: 10.3390/waste1010005
Authors: Qahtan Thabit Abdallah Nassour Michael Nelles
The waste management field in Middle Eastern and North African countries suffers from multiple drawbacks and chronic problems that require strategic solutions and collaboration among various institutions. Due to a lack of data, a financial deficit, limited economic resources for the municipalities, and singular treatment processes, until recently, waste has been dealt with as garbage that needs to be disposed of, while, in a large number of developed countries, waste now represents a substantial economic resource and an important source of materials that can be reinserted into the industrial sector. This paper presents a review of several aspects and sectors that are directly related to waste generation and the current situation regarding the waste management system in the Middle East and North Africa (MENA) region in terms of composition, generated amount/capita, existing treatment routes, and institutional frameworks. Furthermore, gross domestic production and population growth are specified as critical factors governing the waste sector in the region. Such data and information will increase the possibility of drawing a roadmap to convert the current waste treatment stream into a material flow concept and circular economy. The energy sector (energy consumption) is also considered to illustrate the potential role of waste if incineration technology (energy recovery from waste) is realized as a radical solution for the waste system in the region. Following a review of the literature, the main challenges in the waste management sector that need to be solved are summarized. The novelty of this work is two-fold. First, it elucidates the connection between gross domestic product (GDP), waste composition, and waste generation. According to the literature, countries with a high GDP produce a greater amount of waste (around 1.5–2.7 kg/capita/day) with a lower organic share of waste composition of around 40%, as they have an increased lifestyle rate. Second, a review of energy consumption per capita illuminates the essential role of waste as a source of energy.
]]>Waste doi: 10.3390/waste1010004
Authors: Yujie Xue Mingqi Zhang Jizhi Zhou Yufeng Zhang
Aluminum dross (AD) is a hazardous waste that contains valuable metallic Al and reactive aluminum nitride (AlN). The intergrowth of Al and AlN presents a challenge to Al recovery and AlN removal. In the current work, a mechanical milling method was developed to separate Al and AlN. Steel bars and balls were used as grinding media. The AD particle size decreased after milling and was distributed in the ranges 0.425–2 mm, 0.15–0.425 mm, 0.08–0.15 mm, and <0.08 mm. The particle size distribution was affected by the ball milling media and grinding time. Steel ball media had a better grinding effect on particles > 2 mm. After ball milling, the Dp0.08–2 mm size fraction accounted for approximately 90%. With changes in particle size, the element content of AD varied: the fraction of metallic Al decreased, while the fraction of Si increased. Metallic Al mainly existed in particles with size > 0.425 mm, accounting for 48.5%. AlN mainly existed in Dp0.15–0.425 mm, accounting for 64.9%. The optimal milling conditions achieved a 65% Al recovery rate and a 90% AlN separation efficiency. This work provides a promising approach for highly efficient pretreatment for AD recovery and AlN elimination in industrial applications.
]]>Waste doi: 10.3390/waste1010003
Authors: Samsun Nahar Mala Sian Ryan Larder Fiona L. Hatton Elliot Woolley
Reuse of plastic packaging for food is a promising route to reduce the environmental burdens, but presents particular challenges due to the need to avoid cross-contamination of contents. This study investigates the challenges associated with cleaning and assessing existing recycled PET (rPET) food-to-go (FTG) pack forms and provides recommendations to enable a shift towards reusable food packaging systems. Pack forms were fouled under controlled conditions and washed in accordance published guidelines. Three fouling media were selected to represent food residue typically found in FTG packs. Investigated parameters included fouling type and quality, wash and rinse times, and detergent dosage. Cleanliness was assessed using adenosine triphosphate (ATP) swabbing and the effect on the material properties was studied via tensile testing, IR spectroscopy and differential scanning calorimetry. The results demonstrate that cleaning effectiveness is dependent on the quantity of fouling, the duration of the wash cycle and the dosing of detergent indicating the potential to optimise parameters for different fouling conditions. It is also concluded that ATP testing is an inappropriate cleanliness assessment method for food packaging due to many opportunities for it to produce false negative readings, its high cost, and slow response. The rPET material properties remained largely unchanged apart from a slight increase in stiffness, however packaging suffered significant deformation.
]]>Waste doi: 10.3390/waste1010002
Authors: Anne Shayene Campos de Bomfim Daniel Magalhães de Oliveira Eric Walling Alexandre Babin Grégory Hersant Céline Vaneeckhaute Marie-Josée Dumont Denis Rodrigue
As an everyday beverage, coffee is consumed worldwide, generating a high amount of waste after brewing, which needs attention for its disposal. These residues are referred to as spent coffee grounds (SCGs), which have been shown to have applications as polymers/composites precursors, biofuels, and biofertilizers. This review focuses on agricultural applications usually based on organic matter to fertilize the soil and consequently improve plant growth. To date, SCGs have been shown to exhibit outstanding performance when applied as soil amendment and composting because it is a nutrient-rich organic waste without heavy metals. Therefore, this review presents the different options to use SCGs in agriculture. First, SCG composition using different characterization techniques is presented to identify the main components. Then, a review is presented showing how SCG toxicity can be resolved when used alone in the soil, especially at high concentrations. In this case, SCG is shown to be effective not only to enhance plant growth, but also to enhance nutritional values without impacting the environment while substituting conventional fertilizers. Finally, a conclusion is presented with openings for future developments.
]]>Waste doi: 10.3390/waste1010001
Authors: Jisuk Kang
Human activity generates waste, which is discarded after its use and has an unavoidable impact on the environment and on humans [...]
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