Steel is an ideal recycling material as it can be recycled almost indefinitely, and steel recycling is a lot more energy-efficient than iron ore steel production. Steel making with usage of steel scrap in electric arc furnaces is heavily influenced by contaminants in the scrap, including non-ferrous metals, stones, or plastic. To produce high-quality steel, it is important to know what contaminants are part of the scrap to adapt the recycling process accordingly. This work presents a three-part processing pipeline to determine the scrap composition and optimise the recycling process parameters. The first part is hyperspectral imaging, recording images with 437 spectral bands in the short-wave infrared range. Next, deep learning-based image recognition, with multilayer perceptron, 2D and 3D convolutional neural networks (CNNs) have been compared. The 3D-CNN showed the best performance in detecting the 14 material classes in the scrap samples. Finally, a mixed integer optimisation is used to select the best scrap mix for the steel classes that are to be produced. The evaluation shows an accuracy of about 76% in detecting the 14 material classes correctly, with a higher accuracy for the steel class. The detected non-ferrous materials determine the scrap class which is input for the optimisation with its constraints that each scrap class has a minimum consumption to prevent storage overflows, and as little energy and additives as possible should be used.
Aviation generates substantial food waste worldwide, yet the focus has mainly been on post-flight waste, leaving upstream production processes in airline catering understudied. This mixed-methods single case study investigated food waste composition, hotspots and drivers in a Swedish airline catering kitchen, and assessed associated environmental (carbon), economic (procurement cost) and social (nutritional) impacts. Over 21 weekdays, waste audits recorded 1.39 tonnes of food waste, largely edible (89%), corresponding to 3.1 tonnes of carbon dioxide equivalents, €9250 in procurement costs, and 93 kg of protein and 29 kg of dietary fibre losses. Hot kitchen operations, trolley waste and crew meals were the main hotspots, accounting for most edible waste and associated impacts. A divergence between volume-driven and intensity-driven hotspots was found, with vegetables and staple foods driving economic losses and fibre waste, and animal-based foods dominating climate impacts and protein losses. Notably, staple foods emerged as a balanced hotspot across several impact dimensions. Semi-structured staff interviews (n = 8) identified overly strict food safety routines, late airline and crew changes, forecasting mismatches, and coordination gaps as key structural drivers of waste, leading to recurrent overproduction and limited flexibility in meal handling. By shifting attention from downstream to upstream, the study shows that targeting kitchen-stage processes offers a viable route to reducing avoidable waste by addressing systemic inefficiencies and rigid safety buffers. Integrating contractual cut-off times for order changes into procurement and governance measures that encourage shared responsibility for waste prevention offers a pathway to improving resource efficiency while maintaining food safety and service standards.
There is a significant global rise in the amount of waste electrical and electronic equipment (WEEE). This waste typically contains more than 20% plastic, which can have significant environmental benefits if properly treated and recycled. However, recycling plastics from WEEE is a challenging task due to the complexity of the waste composition, which consists of several polymers, many of which contain heavy metals, additives, and brominated flame retardants. This study presents both technical and environmental concerns in the resource recovery of WEEE plastics. Based on results of a prior research on the composition of waste electrical and electronic plastics (WEEP) in Finland, this study assess the environmental impacts associated with the recovery of WEEP by comparing four technically available WEEP treatment methods: energy recovery (incineration), mechanical recycling of composite plastics, mechanical recycling for separated polymers, and chemical recycling by pyrolysis. This study concludes that mechanical recycling with plastic separation has the best environmental performance among the presented scenarios for all selected impact categories except for the acidification potential impact category. The substitution ratio of virgin plastics and the efficiency of the pyrolysis process were the primary factors contributing to the environmental impacts of WEEP treatment options.
Municipal waste generation remains a key obstacle to Europe's transition towards a circular economy and to the achievement of Sustainable Development Goal 12, particularly in macro-regions where European Union (EU) Member States coexist with Western Balkan countries. The Adriatic-Ionian region provides a critical testing ground to assess whether economic growth continues to translate into higher municipal waste generation or whether meaningful decoupling has begun to emerge. This paper examines the extent to which municipal waste generation is driven by economic development between 2008 and 2023, and whether the underlying drivers differ between EU Member States and Western Balkan countries. Using a balanced panel of eight countries, the analysis combines fixed-effects econometric modelling with a decoupling assessment and a regional interaction approach. Results indicate that, once country-specific and time-specific factors are accounted for, economic growth alone does not systematically increase municipal waste generation. In contrast, environmental protection expenditure consistently reduces waste levels, underscoring the central role of policy effort. The analysis also reveals pronounced regional differences. These findings are directly relevant to SDG 12 and offer actionable evidence for three domains of application: (1) for EU cohesion and pre-accession policy design, supporting the case for prioritising environmental funding in Western Balkan countries; (2) for macro regional governance under European Union Strategy for the Adriatic-Ionian Region (EUSAIR), where the evidence of distinct waste growth regimes calls for differentiated decoupling strategies; and (3) for national waste management planning, where investments in environmental awareness and tertiary education should complement infrastructure development to accelerate waste prevention.
This study aims to analyze waste disposal and recovery data for 2022 and 2024 in Türkiye to reveal changes in national waste management and to make future predictions using multivariate machine learning and artificial neural network (ANN) models. Trends in disposal and recovery capacity were identified, and the main variables affecting waste processing volumes were modeled. Multiple linear regression and feedforward ANN models were created using the capacity and processing quantities obtained from Türkiye İstatistik Kurumu's data. The ANN model was trained with three hidden layers and a 64-32-16 neuron structure, with a learning rate of 0.001. The dataset was divided into 80% training and 20% testing. The machine learning model's test set accuracy coefficient was calculated as R2 = 0.87, and the mean absolute error (MAE) was 1.96 million tons. The ANN model demonstrated even higher performance, reaching R2 = 0.93 and an MAE of 1.41 million tons. ANNs accurately predicted total recycled waste to be 51.5 million tons in 2024, while the amount of landfilled waste was predicted with only a 3.2% margin of error. Model analyses revealed that increasing landfill capacity significantly increases disposal volume, while increasing the number of recycling facilities affects recovery volume through a strong, nonlinear relationship. The results show that ANN models can predict Türkiye's waste management trends with high accuracy and prove that they provide a powerful decision support tool that can be used in future policy planning.
Biogas desulfurization is essential to prevent equipment corrosion and ensure its suitability for energy applications. Although several technically established desulfurization technologies are commercially available, their implementation may still be constrained by acquisition costs, operational expenses, and environmental impacts associated with the use of conventional materials such as activated carbon. In this context, this study investigates the potential of two abundant agro-industrial residues - Luffa cylindrica and Carya illinoinensis - as low-cost and environmentally favorable filter media for biofilters applied to biogas desulfurization. A pilot-scale system operated for 62 days treating biogas with H2S concentrations above 5000 ppm, and their performance was compared with that of a conventional activated carbon filter. Both biofilters demonstrated high initial removal efficiencies, reducing H2S concentrations in the treated gas to below 20 ppm. Over time, the loofah-based filter showed a decline in performance due to sulfur accumulation, whereas the pecan shell medium exhibited greater operational stability and indications of self-regeneration, achieving performance statistically comparable to that of activated carbon. These results highlight the technical feasibility of using abundant agro-industrial biomass as alternative biofilter media, contributing to reduced operational costs and lower environmental impacts in biogas purification systems. The findings also reveal opportunities for integrating biomass waste valorization with biogas purification technologies, indicating promising pathways for more sustainable and economically accessible desulfurization strategies in decentralized and industrial biogas applications.
Leachate pumping has been widely adopted in landfill engineering. The removal of leachate from the waste mass modifies the internal moisture content and generates convective flow, which unavoidably leads to variations in waste temperature. These temperature changes subsequently influence the degradation behaviour of the original waste. In this study, based on the previously completed leachate pumping test, the associated fluctuations in leachate level and waste temperature evolution during the pumping process were simulated. An axisymmetric saturated-unsaturated seepage model was established for high-level landfills, incorporating depth-dependent variations in permeability and porosity. Additionally, an axisymmetric heat convection-conduction model was developed, taking into account both the impact of seepage on temperature distribution and the influence of moisture content on waste degradation. The governing models were solved using numerical calculation methods. Comparisons between the calculated results and test data indicated that the proposed models and solution approach accurately captured the trends in leachate level variation and waste temperature changes induced by leachate pumping. The results suggest that, under single-well pumping conditions, the degradation duration of newly placed waste and the specific heat capacity exerted a relatively pronounced effect on temperature distribution. Waste permeability exhibited a negligible influence on temperature gradients outside the zone of influence; however, it played a decisive role in determining the magnitude of temperature variation within the affected area. The models developed in this study provide a theoretical basis for evaluating temperature distributions under leachate pumping conditions and offer important guidance for landfill operation, expansion and closure.
Determining the composition of demolition debris is crucial for effective waste management and post-disaster recovery planning. This study had two main objectives: (i) the characterization of demolition waste (DW) originating from post-earthquake controlled demolitions (as opposed to collapsed buildings), and (ii) the investigation of how building age and seismic codes influence on debris composition. A field investigation was conducted in Malatya, one of the provinces affected by the 6 February 2023 earthquakes in Türkiye, to evaluate the valorization potential of DW. Debris from nine controlled demolitions representing buildings constructed before 2000, between 2000 and 2011, and between 2011 and 2018 was collected and characterized. Additionally, three truckloads of mixed piles were sampled from the temporary storage area. In total, 490 tonnes of material were analysed by mass percentage. The results show that mineral fractions consistently dominate (≈94-97% by mass), whereas iron exhibits the highest variability depending on construction period (1.69-3.48%). Other fractions such as wood, textiles, plastics, paper and cardboard, metals and electronics, and bulky items collectively account for less than 5% of total mass. This systematic field study provides an essential baseline for understanding DW composition in post-earthquake controlled demolition contexts and supports future research on the valorization and sustainable management of construction debris in Türkiye and other earthquake-prone regions in the world.
Motorcycles are not only vital to transportation and economies in many Southeast Asia's countries but also cause substantial air pollution. As alternative electric mobility is increasingly promoted by countries, managing end-of-life (petrol) motorcycles (EoLMs) becomes more urgent. This article addresses the question: How will EoLMs be treated, transformed or disposed of? Vietnam, leading the region in motorcycle ownership, was selected as the case. The authors used a triangulation approach, combining literature review, site observations and semi-structured interviews to examine Vietnam's EoLM recycling management. Specifically, the article provided motorcycle-related estimations to fill the data gap, based on which numerical warnings on emissions from in-use EoLMs were generated to support the contemporary emission picture. Advantages and limitations of the current legislative framework and recycling system were identified. Finally, a tailored recycling management framework was proposed, incorporating mandatory emission testing, enhanced extended producer responsibility regulations and subsidies for the industry. This study contributes to the limited literature on EoLM management and provides policymakers with an interdisciplinary framework emphasizing stakeholders' collaboration.
Municipal solid waste management (MSWM) remains a critical challenge in India due to rapid urbanisation, increasing waste volumes, and limited institutional capacity. Although urban local bodies (ULBs) allocate up to 80% of their MSWM budgets to collection and transport, inefficiencies persist due to unoptimised routes and poor alignment with local conditions. Most geographic information system (GIS)-based optimisation models remain top-down, failing to reflect on-the-ground realities and are rarely implementable. This study presents a participatory GIS-based routing methodology for decentralised MSWM system in a flood-prone town in Kerala, India. It integrates standard geospatial data with tacit knowledge from ULB officials and frontline sanitation workers through participatory mapping and ground-truthing, producing spatial layers on waste generation, transport conditions, flood-prone roads, and existing collection clusters, pick-up points, and storage facilities. Based on this, the study proposes operational changes, including new pick-up points, mini-material collection facilities (intermediary storage hubs), and a three-tier vehicle system tailored to local constraints. ArcGIS Network Analyst is used to identify optimal routes, incorporating flood-prone roads as network barriers. Compared to the current system, the optimised plan is flood-resilient and achieves a 32% reduction in travel distance, 35% cut in fuel use and emissions, and a 62% increase in collection capacity and 100% household coverage, along with better working conditions. The study offers a scalable framework that merges technical optimisation with context specificity, enabling ULBs in resource-constrained settings to co-produce climate-resilient transport solutions.
Hydrogen sulphide (H2S) is a hazardous gas that requires effective removal. In this study, biochar derived from vegetable-tanned, chrome-free leather industry residues was produced via pyrolysis at controlled temperatures 750°C and chemically activated using KOH and NaOH (ratios 0.36:1-3:1) to evaluate porosity development and surface chemistry modifications. Additionally, different washing methods (acid, alkaline, and hot water) were tested, with hot water washing proving effective in preserving oxygen functionalities in the optimal sample. The obtained activated biochar, with Brunauer-Emmett-Teller surface areas of up to 2660 m2/g, were evaluated as a sustainable alternative to commercial adsorbents for H2S removal. Adsorption experiments revealed that KOH-activated biochar exhibited the highest H2S uptake, reaching 288 mg/g, outperforming conventional coal-based activated carbons (ACs; 150 mg/g). The activation process significantly influenced material properties and adsorption efficiency, with KOH activation leading to enhanced microporosity, increased surface basicity, and improved gas-solid interactions. The study also examined adsorption mechanisms, highlighting the contributions of physisorption, chemisorption, and catalytic oxidation in sulphide retention. These findings demonstrate the potential of biochar-based adsorbents for gas purification applications. In addition, a techno-economic assessment supports the feasibility of utilizing biochar as a cost-effective and sustainable alternative to fossil-based ACs, with an estimated removal cost of $4.2 per kilogram of H2S, reinforcing its role in waste valorization and circular economy strategies.
The extraction of metallic aluminum from incineration bottom ash (IBA) has twofold implications: to obtain aluminum for the recycling industry and to reduce the content in the treated mineral fraction for its utilization as aggregate in concrete. This study used IBAs from fluidized bed (FB) and grate (G) municipal solid waste incineration for two full-scale experiments, investigating the flows of metallic aluminum in a dry-wet IBA treatment process. Metallic aluminum >4 mm was determined by hand sorting, while <4 mm was determined by the soda-attack method. Extraction rates into metal concentrates of 97% for FB-IBA and 78% for G-IBA were achieved, demonstrating the plant's ability to treat both types of IBA. The elevated extraction rate for FB-IBA is attributable to the dry IBA discharge and the reduced bed temperature. These factors preclude the melting of aluminum, glass, and minerals, resulting in the presence of aluminum particles that are entirely liberated from the mineral phase of IBA, which is advantageous for eddy current separation. Consequently, low residual metallic aluminum contents in the treated mineral fraction (0-8 mm) of 0.5 wt-% in FB-IBA and 1.0 wt-% in G-IBA were determined. Nevertheless, to draw conclusions on the usability in concrete, it is imperative to implement continuous monitoring of the residual metallic aluminum content to substantiate these values, given their reliance on sound plant operation as well as on the initial IBA composition, which knowingly exhibits significant fluctuations.
Littering in natural open spaces presents persistent environmental, social and economic challenges, despite the implementation of various policies. Littering behaviour emerges from the interaction of multiple determinants and is strongly shaped by environmental, situational and personal conditions. To examine the influence of multiple determinants, the present study was designed as a quantitative multi-method field design. Structured behavioural field observations of 2262 visitors yielded 411 documented behavioural events, classified as intentional littering, unintentional littering and anti-littering behaviour. These were analysed alongside 624 linked post-event questionnaires across 26 nature sites in Israel. Forty-two environmental, situational and personal determinants were examined using multinomial logistic regression. Situational determinants, particularly litter type, emerged as the strongest predictor of observed littering behaviour, followed by environmental conditions such as maintenance levels and waste bin availability. In contrast, personal determinants, including attitudes and perceived responsibility, demonstrated limited predictive power when tested against directly observed behaviour. The results highlight the strong situational sensitivity of littering behaviour and reveal a gap between attitudes and observed behaviours in natural settings. The findings provide clear guidance for prioritizing waste management interventions in nature sites.
Dairy industry waste is a stream within the agri-food sector that requires sustainable management solutions. It is also a significant source of valuable nutrients that can be effectively recovered and valorised through sustainable environmental technologies within a circular bio-based economy. This study presents a chemical valorisation approach to produce an amino acid-rich biostimulants from dairy industry waste. Acid hydrolysis parameters, including the proportion of the hydrolysing medium (X1: 10-30%), acid concentration (X2: 10-100%), and temperature (X3: 20°C-100°C), were optimised using response surface methodology with a Box-Behnken design. Neutralised hydrolysates (pH ~5) yielded 15 suspensions, modelled by a second-order polynomial (R2 = 0.9989). Optimal conditions (X1: 10%, X2: 10% H2SO4:H3PO4, X3: 100°C) produced 64.5 g kg-1 amino acids. Physicochemical and microbiological analyses confirmed a high nutrient load and significant microbial reduction (<1.00 × 101 CFU g-1), ensuring environmental safety of the hydrolysates for agricultural application. Germination tests on cucumber (Cornichon de Paris) showed enhanced root development and biomass. The best formulation increased seedling fresh mass by 47% over the control and 27% over a commercial product. This valorisation strategy allows for effective recovery of resources while reducing the environmental burden of dairy waste and supporting the integration of industrial by-products into sustainable agricultural practices. This research highlights a path consistent with sustainable waste management in line with the circular economy.
The generation of municipal solid waste (MSW) has risen sharply, posing increasingly complex environmental challenges, particularly in its final disposal in landfills. Among the various contaminants present in MSW, emerging pollutants such as silver nanoparticles (AgNPs) are of particular concern. In this context, this study investigated the influence of AgNPs at concentrations of 50, 150 and 450 mg·kg⁻¹ on MSW biodegradability and leachate characteristics using pilot-scale reactors (lysimeters) simulating landfill conditions. Four pilot reactors were monitored over 18 months for biogas generation, physicochemical parameters of the leachate and microbial community structure. The results showed that in the 18 months evaluated, AgNPs did not affect biogas production, with low methane generation observed in all reactors, consistent with early stages of anaerobic digestion. However, increasing AgNPs concentrations were associated with qualitative changes in the microbial community. Overall, the results highlight the relevance of AgNPs as emerging contaminants in landfill environments.
Polyethylene terephthalate (PET) and epoxy resin (ER) are commonly used polymers that are frequently combined in many applications, posing significant challenges for their separation and recycling. Pyrolysis is an effective technology for organic waste recycling by thermal processing, and the co-pyrolysis of composite materials or mixtures may offer potential advantages in improving pyrolysis efficiency and product values. The specific performance of PET-ER co-pyrolysis is not yet clear. This study aimed to elucidate this process through a comprehensive investigation of the pyrolysis process and product characteristics. Thermogravimetric-differential thermogravimetric analysis demonstrated an interaction between PET and ER during pyrolysis. For example, the residue yield and apparent activation energy of P8E2 (a mixture with PET-ER mass ratio of 8:2) decreased by 7.46% and 14.83 kJ·mol-1, respectively, compared to the theoretical values. Pyrolysis experiments identified the suitable operating conditions for P8E2 as pyrolysis temperature of 450°C and holding time of 30 minutes. Gas chromatography-mass spectrometry analysis identified benzoic acid and its derivatives as the primary components of the pyrolysis oil, which suggests a radical-mediated mechanism and confirms the synergistic interactions between PET and ER, and combustible gases (CO and CH4) were the main components in the gaseous product. The results of this study would provide valuable insights into the recycling of multicomponent plastic mixtures and contribute to the advancement of pyrolysis technology, offering practical implications for the treatment of complex organic solid waste.
Informality is one factor associated with solid waste management in developing countries. Studies are scarce on the implications of these informalities to macro-level circular economy (CE) adoption in these global regions. Contributing to this gap in knowledge, this study analyzed Nigeria's informal waste management sector to appraise its contribution to the waste management value chain in the CE. It also evaluated the associated challenges and opportunities that could facilitate or hinder its adoption in macro-level CE implementation. The result of the study shows that informal waste sectors contribute significantly to the waste management value chain such as collection, transportation, sorting, upcycling, resource recovery, and recycling. The informal waste collection, which is currently the only means of collecting recyclables in Nigeria is estimated to collect about 3.35 million tonnes (Mt) in 2030 from the current value of 2.69 Mt in 2023. It has the potential to make economic savings of about $121.48 million and add a net revenue of $454. 41 million to the national economy by 2030. Given these contributions, other identified opportunities for including the informal waste sector in the macro-level CE include; providing a source of livelihood to socially marginalized urban populations while promoting environmental sustainability; providing waste collection services to unserved urban areas, creating a circular business model, creating a platform for possible transition to zero waste status, aiding the implementation of extended producer responsibility, and providing cheap input material for local industries. The challenges include harsh work conditions and social capital, non-standardized metrics for the trade of recyclables, unavailability of data, poor quality recyclables caused by not segregating waste from source, child waste picker, gender exclusiveness, and absence of novel waste treatment facilities.
In Nigeria, e-waste management is predominantly handled by the informal sector, which relies on crude methods, causing environmental and health risks. E-waste Producer Responsibility Organization of Nigeria (EPRON) conducted a study focused on informal e-waste collection and management practices, aiming to inform the development of a sustainable, circular e-waste management system. The study surveyed 495 informal operators and found that most e-waste collectors are male (96.8%) with an average age of 33 years. Awareness of e-waste regulations is low, with 61.6% unaware of existing regulations and 58.2% unaware of the ban on e-waste imports and cathode-ray tube (CRT) devices. Despite this, 63.6% of collectors are aware of the importation of used electrical and electronic equipment, most of which is non-functional. House-to-house collection is the most common source of e-waste (55.2%), followed by shops (19.6%) and offices (14.1%). Televisions, mobile phones, freezers, and pressing irons are the most frequently collected items, and 84% of collectors compensate consumers for e-waste. Door-to-door collection is the preferred method for 54% of collectors, while only 11% collect from dumpsites. Items such as plastics, CRT glass, bulbs, and phone screens are rarely collected. Most collectors engage in pre-processing activities, using manual dismantling to recover valuable materials, with 44% transferring e-waste to major collection centres. However, 68% of collectors do not keep records while only 51.5% of collectors regularly use personal protective equipment. Improving informal e-waste management in Nigeria requires targeted awareness raising on the legal recognition of e-waste and the penalties associated with its indiscriminate handling. Improving collection infrastructure, designing improved incentives for adhering to formal collection and recycling channels, training of collectors, enforcing regulations, and collaborating with stakeholders are highly recommended.
Separating food waste supports a more circular economy. As the most visible part of the value chain, the collection system plays a key role in waste management performance. This study quantifies the environmental impacts of various food waste collection methods using life cycle assessment, focusing on climate change and potential trade-offs across other impact categories. Two different treatment alternatives were explored: composting and anaerobic digestion (AD). The functional unit was defined as the management of the average amount of food waste generated per person during a year in Norway. The results show that the collection strategy affects both sorting rate and environmental performance. Climate change impacts range from -9.7 to -7.5 kg CO2 eq./person/year for AD and between -6.3 and 2.5 kg CO2 eq./person/year for composting. Collection in paper bags in separate containers results in the lowest climate change impact for both treatment pathways, but may increase other environmental impacts. For the AD pathway, there are relatively small differences between the results for the studied collection options. The use of paper bags, however, is likely to be the only option that eliminates the risk of plastic pollution in the soil from bags. The study identifies a potential "separate container effect": a higher separation rate is achieved with separate containers compared to the optical bag sorting system. This emphasizes how crucial the choice of collection method is for effective food waste management.
Improper treatment of hospital wastes is currently attracting considerable attention due to their infectious and hazardous nature. This study assessed the generation, composition, isolation and identification of bacteria in waste from a tertiary hospital in Abeokuta, Southwestern Nigeria. The quantity of waste generated daily in the hospital was determined for 4 months (2 months each in wet and dry seasons). The wastes were later segregated and categorized into general, infectious, highly infectious, pharmaceutical, pathological, chemical and sharp waste in line with the World Health Organization specifications. Samples of hospital wastes from six selected sections within the hospital were collected and subjected to microbiological examinations. The microorganisms isolated from the waste were identified using deoxyribonucleic acid (DNA) extraction and sequencing. The total quantity of waste generated in the hospital during the study period was 13,101.32 kg (6894.92 and 6206.40 kg for wet and dry seasons, respectively). The waste generated per day was 106.51 kg, whereas the quantity of waste generated per bed per day and the quantity of waste generated per patient per day were 0.35 and 0.24 kg, respectively. The DNA extraction and sequencing confirmed the presence of Alcaligenes faecalis, Lysinibacillus fusiformis, Pseudomonas aeruginosa and Bacillus thuringiensis in the hospital waste. Wastes generated in the hospital were hazardous, and physical composition and classification of the medical waste did not vary with season.
