Waste, Volume 3, Issue 1 (March 2025) – 10 articles

Currently, the generation of electricity in most countries around the world primarily relies on fossil fuels, which contribute significantly to environmental degradation and climate change. Municipal solid waste (MSW) presents a promising alternative energy source, as various technologies now exist to treat waste and recover its energy. This shift helps to reduce reliance on non-renewable resources and tackles the growing issue of waste management. This article comprehensively reviews three waste-to-energy technologies: anaerobic digestion, gasification and plasma gasification. It covers the fundamental principles behind each technology, their efficiency in energy recovery, the associated costs and their practical applications. Additionally, the article delves into the technical challenges faced in implementing these technologies, such as their scalability, economic feasibility and environmental impacts. By evaluating these technologies, the article aims to provide insights into their potential for contributing to a more sustainable and circular energy system. Full article

In processing mixed commercial waste (MCW), particle size distribution is as critical as material composition. Detailed knowledge of particle size distribution unlocks the recycling potential of specific material groups and facilitates the efficient conversion of these materials into secondary fuels. Additionally, understanding particle size-dependent element distribution in waste is crucial, particularly given potential legal limits on several heavy metals. While two studies carried out in 2019 have addressed these issues, the inherent variability in MCW composition necessitates further investigation to validate and expand upon these findings. In this study, ten representative samples of MCW were collected and screened with eight screen cuts (200 mm, 100 mm, 80 mm, 60 mm, 40 mm, 20 mm, 10 mm, 5 mm). Six of these fractions (>20 mm) were sorted into 37 material classes, combined again by particle size, and subjected to chemical analyses. These analyses included essential fuel parameters, such as lower heating value and biogenic carbon content, and the concentration of 35 elements across all particle size fractions. A Mann–Whitney U test was conducted to identify correlations in element concentrations between the present study and the study carried out in 2019. Although the results confirm considerable variability in MCW composition, they also reveal trends in element concentrations related to calorific value. Full article

This study introduces a novel two-stage circular economy model to transform organic waste materials—bean dregs and coffee grounds—into functional products: eco-friendly cat litter and organic fertilizer. The hypothesis was that integrating vermicompost and diatomaceous earth with these waste materials would enhance the functional properties of cat litter while ensuring its recyclability into high-quality fertilizer. In the first stage, a combination of bean dregs, coffee grounds, vermicompost, and diatomaceous earth was optimized using the Taguchi method, achieving cat litter with superior water absorption and clumping performance. In the second stage, the spent cat litter was rapidly composted, producing a nutrient-rich organic fertilizer. The fertilizer’s efficacy was validated through a potting experiment with lettuce, where a 10% application rate promoted optimal growth without causing nutrient toxicity. This innovative approach offers a sustainable solution to waste management challenges while contributing to environmentally friendly agricultural practices. Future research could investigate incorporating additional waste streams and enhancing composting efficiency for broader implementation. Full article

Water pollution from herbicide contamination poses a significant environmental challenge, necessitating effective regenerative materials for their removal. 2,4-dichlorophenoxyacetic acid and glyphosate are among the most widely used herbicides for weed control. This study aimed to synthesize polymeric materials for the removal of these compounds from aqueous media. The study evaluated adsorption capacity, isotherms, kinetics, regeneration capacity, and the influence of pH on adsorption, alongside disinfection tests. Biodegradable polymers including chitosan, sodium alginate, and guar gum were cross-linked and characterized using infrared and Raman spectroscopy. Two samples (experiment C and M) exhibited adsorption capacities of 49.75 ± 1.474 mg g⁻¹ and 26.53 ± 1.326 mg g⁻¹ for glyphosate and 2,4-dichlorophenoxyacetic acid, respectively. Optimal adsorption was observed at pH 3.00 and 6.00 for glyphosate and 3.00 for 2,4-dichlorophenoxyacetic acid. The Langmuir and Dubinin–Radushkevich isotherms best described the adsorption behavior of glyphosate and 2,4-dichlorophenoxyacetic acid, respectively. Kinetic studies indicated that the adsorption process followed a pseudo-second-order model. Infrared and Raman absorption spectra confirmed cross-linking in the polymer samples. Regeneration tests showed that 2,4-dichlorophenoxyacetic acid adsorption remained consistent over three reuse cycles, while glyphosate adsorption increased. Disinfection tests using Escherichia coli and total coliforms demonstrated a significant reduction in colony-forming units, supporting the suitability of the material for this application. Full article

In sub-Saharan Africa, municipal solid waste management faces significant challenges, including inadequate infrastructure, increasing waste generation, and limited resources, leading to severe environmental and public health issues. Innovations in waste management are essential to address these pressing problems, as they can enhance efficiency, reduce pollution, and promote sustainable practices while fostering sustainable development. To select sustainable and contextually relevant solutions, it is vital to investigate their potential sustainability impacts based on the Sustainable Development Goals (SDGs) beforehand and to involve local stakeholders in the innovation process. Besides, engaging stakeholders increases community buy-in and fosters collaboration, leading to more effective and sustainable outcomes. This paper develops and applies a sustainability assessment methodology for innovations in municipal solid waste management systems in sub-Saharan Africa, with a case study in Ethiopia. The proposed methodology emphasizes the importance of involving local stakeholders in the SDG-based indicator assessment and offers suggestions for a data collection strategy. The case study on a composting process in Bishoftu Town demonstrates that stakeholder participation in selecting innovations positively influences the outcomes. However, the analysis indicates mixed effects of the innovation in the three sustainability dimensions, highlighting areas for optimization. Consequently, the presented method can support the innovation process of municipal solid waste management systems, fostering sustainable municipal development. Full article

The mechanism of slagging in municipal solid waste incinerators is complex, and the slagging process is simultaneously affected by the composition, temperature, and flue gas flow. In this study, slag samples on a water-cooled wall were first analysed, and the key components and fusion temperatures were measured. Second, a gas-phase combustion model of an incinerator was established, and the temperature and velocity distributions of the flue gas inside the incinerator were calculated. Based on the incineration process, coupled with a discrete-phase model, a numerical simulation model of the slagging process on the water-cooled wall of the incinerator was constructed, considering the transport and adhesion processes of ash particles. The influence of parameters such as the ash particle size and concentration on the degree of slagging on the water-cooled wall was analysed. Smaller ash particles were less likely to adhere to water-cooled walls, with approximately 2.72% of ash particles with a particle size of 10 mm adhering to water-cooled walls. The proportion of ash particles with a particle size of 50 mm adhering to water-cooled walls was approximately three times that of those with a particle size of 10 mm. As the concentration of ash particles increased, the number of ash particles adhering to the water-cooled wall increased, and the adhesion ratio decreased. These results are of great significance for optimising the operation of incinerators and reducing slagging rates. Full article

This study investigates the properties of Benitaka grape pomace (Vitis vinifera L.), a byproduct of the wine industry, focusing on its potential for applications in the circular economy and biorefinery processes. The analysis covers a range of physical, chemical, and structural characteristics, including the composition of proteins, moisture, lipids, ash, sugars, fiber fractions (such as neutral-detergent fiber, cellulose, lignin, and hemicellulose), pH, acidity, gross energy, as well as bioactive compounds such as total phenolics, flavonoids, anthocyanins, and antioxidant capacity. Advanced characterization techniques, such as nitrogen adsorption/desorption isotherms, Fourier-transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy, and high-performance liquid chromatography coupled with mass spectrometry, were employed. The results revealed an acidic pH of 4.05 and a titratable acidity of 1.25 g of tartaric acid per 100 g. The gross energy was 3764 kcal kg⁻¹, indicating high energy capacity, similar to wood chips. The pomace exhibited high hygroscopicity (31 to 50 g of moisture per 100 g), high levels of fiber, cellulose, and lignin, as well as bioactive compounds with significant values of total phenolics (5956.56 mg GAE 100 g⁻¹), flavonoids (1958.33 mg CAT 100 g⁻¹), and anthocyanins (66.92 mg C3G 100 g⁻¹). Antioxidant analysis showed promising results, with DPPH and FRAP values of 20.12 and 16.85 μmol TEAC g⁻¹ of extract, respectively. This study not only validates existing data but also provides new insights into the composition of hemicellulose and lignocellulosic phase transitions, highlighting grape pomace as a promising resource for sustainability in industry and biorefinery processes. Full article

To verify the possible roles of calcium peroxide (CaO₂) in addressing the key challenges of aerobic composting of food waste, including long composting duration, poor compost product quality, and gas emissions during composting, this study conducted a 38-day composting experiment using artificially blended food waste. Five containers were employed for investigating the effects of five doses of CaO₂ (0%, 5%, 10%, 15%, and 20%, w/w) on physicochemical parameters, organic matter (OM) degradation, and humification during composting. Additionally, more evidence from a microbial perspective was provided by analyzing the effects of CaO₂ additions on microbial community succession. The results indicated that CaO₂ additions increased the relative abundance of mineralization bacteria, accelerated the temperature increase of compost in the early composting stage, and elevated the peak temperature. It also facilitated the decomposition of OM and enhanced the synthesis of humic acid during the early composting stage. However, the addition of CaO₂, especially at relatively high doses, impacted the humification process. Compared with the control, only the 5% CaO₂ treatment had a significantly greater humification coefficient, reaching 1.73 ± 0.11. Moreover, adding CaO₂ reduced the total ammonia emissions from composting by 17.1% to 59.7%. Overall, CaO₂ is an effective additive for ameliorating key issues in food waste composting. Full article

This study investigates key demographic and behavioural factors influencing food waste behaviours among Greek consumers, offering insights into effective waste reduction strategies. Using k-means clustering, Greek consumers were segmented into three groups based on data from a structured online survey: ‘Moderate Consumers’, who demonstrate moderate awareness of food waste but lack consistent practices; ‘Indifferent Consumers’, primarily younger urban residents, with limited concern and significant contributions to waste; and ‘Conscious Consumers’, generally older individuals with structured habits that actively minimise waste. The findings reveal distinct engagement levels across these groups, highlighting the importance of tailored interventions. Conscious Consumers can serve as community advocates for sustainable practices, while Indifferent Consumers require targeted awareness campaigns to foster engagement. Moderate Consumers, with their sporadic efforts, could benefit from practical tools such as meal-planning apps. By exploring these unique consumer profiles, this research provides a culturally contextualised understanding of food waste attitudes in Greece and lays the groundwork for designing targeted strategies to encourage sustainable consumption. Full article

The process of purifying agricultural products, at various food processing plants, generates waste materials that consist of precipitated calcium carbonate, organic debris, and trace amounts of soil and agricultural contaminants. A specific food-processing waste, hereafter referred to as a food industry byproduct, FIBP, is typically stockpiled on land adjacent to the corresponding food processing facilities due to its large volume and chemical composition. The FIBP also contains commercially available unspent lime products, which makes its reuse viable in various applications. An example is construction applications where an organic content of up to 5% by weight is allowed, such as treating expansive clays. Traditionally, lime stabilization has been used for improving the properties of expansive clays, where ground improvement methods are necessary for a large area. However, the process of producing lime is resource- and energy-intensive as it includes crushing and heating limestone in kilns to extract lime. Therefore, one specific doubly sustainable application is the treatment of expansive clays using the FIBP instead of lime. The main application tested here is the treatment of expansive clayey soils underneath a stretch of State Highway 95 near Marsing, ID. Other potential applications are in road and embankment construction. To evaluate the potential of expansive clay stabilization utilizing the FIBP, a series of geotechnical and environmental laboratory testing were conducted to measure the engineering properties (e.g., swell potential, permeability, and strength properties) of expansive clay amended with FIBP. Preliminary testing on blends with an expansive clay suggests benefits such as decreased swelling potential, increased density, and leachate immobilization. Full article