Search Results (295)

Rapid urbanization in China has driven annual food waste production to 130 million tons, posing severe environmental challenges for anaerobic digestate management. To resolve trade-offs among drying efficiency, resource recovery (fertilizer/fuel), and carbon neutrality by optimizing the biodried product (BDP) recycling ratio (0–15%), six BDP treatments were tested in 60 L bioreactors. Metrics included drying kinetics, product properties, and environmental–economic trade-offs. The results showed that 12% BDP achieved a peak temperature integral (514.13 °C·d), an optimal biodrying index (3.67), and shortened the cycle to 12 days. Furthermore, 12% BDP yielded total nutrients (N + P₂O₅ + K₂O) of 4.19%, meeting the NY 525-2021 standard in China, while ≤3% BDP maximized fuel suitability with LHV > 5000 kJ·kg⁻¹, compliant with CEN/TC 343 RDF standards. BDP recycling reduced global warming potential by 27.3% and eliminated leachate generation, mitigating groundwater contamination risks. The RDF pathway (12% BDP) achieved the highest NPV (USD 716,725), whereas organic fertilizer required farmland subsidies (28.57/ton) to offset its low market value. A 12% BDP recycling ratio optimally balances technical feasibility, environmental safety, and economic returns, offering a closed-loop solution for global food waste valorization. Full article

The global population continues to rise, placing increasing pressure on the agri-food sector and leading to the accelerated generation of urban organic waste, factors that collectively intensify climate stress and environmental instability. Insects are recognised for their remarkable capacity to transform substrates into valuable products, with the black soldier fly larvae (BSFL) emerging as one of the most efficient and widely utilised species for this purpose. Beyond recycling organic matter, BSFL can also mitigate microbial contamination, effectively reducing bacterial and fungal loads in waste substrates. Understanding and manipulating the genome could provide tools to improve BSFL bioconversion process and contribute to sustainability. In this review, we provide an overview of recent advances in black soldier fly genomics and genome-editing technologies. Although research in this subject remains limited, recent studies have clarified its origin, characterised its genome, and established the foundation for targeted genetic improvements to enhance by-product conversion, nutrient recovery, and environmental sustainability. Full article

Microplastics represent an emerging threat to aquatic environments and organisms, as they infiltrate water systems, are ingested by marine species, and cause physical harm, endocrine disruption, and bioaccumulation up the food chain, potentially impacting biodiversity and human health. Aquatic ecosystems face considerable harm from microplastic pollution because fish in the early developmental stages, including embryos, larvae, and juveniles, are more susceptible due to their immature physiological and detoxification systems. This review aims to comprehensively explore the impacts of microplastics on the early life stages of fish. Aquatic environments receive primary and secondary MPs from urban runoff and industrial waste, together with degraded plastics, which affect fish embryos and larvae via direct ingestion, surface adhesion, and trophic transmission pathways. The physical impact of MPs causes digestive tract blockages that reduce hatching success and create developmental problems in fish organs, but chemical toxicity develops from plasticizers, heavy metal leaching, and pollutant adsorption, which causes oxidative stress, endocrine disruption, and metabolic dysfunction. Survival rates decrease because exposure causes fish to perform poorly during swimming activities and make limited efforts to avoid predators. The small dimensions and high chemical reactivity of MPs increase their bioavailability, which promotes tissue penetration and leads to accumulation at different levels of the food chain. This comprehensive review emphasizes that we need to establish uniform detection protocols, long-term exposure research, and effective strategies to control MP pollution. The resolution of these difficulties remains essential for protecting fish populations, as well as for protecting biodiversity and minimizing seafood contamination risks to human health. Full article

There are large amounts of carbohydrates and proteins in rban perishable organic waste (UPOW), which can be converted to short chain fatty acids (SCFAs) through microbial methods. In this study, the mass balance and properties of organic slurry generated from UPOW pretreatment were investigated first. Then, the optimal conditions for SCFAs production from organic slurry of UPOW was studied. It was found that under the conditions of pH 8 ± 0.5 and reaction time of 3 d, the yield of SCFAs, mainly composed of acetic and propionic acids, in the full-scale reactor was 0.68 gCOD/gTCOD of organic slurry. Under the conditions of influent NH₄⁺-N, total nitrogen, soluble ortho-phosphorus, and soluble COD of 27–39, 33–45, 2–9, and 220–300 mg/L, respectively, the use of SCFAs-enriched fermentation liquid (100 mg COD/L) as the additional carbon source for full-scale biological municipal wastewater treatment showed a higher total nitrogen and phosphorus removal efficiency than that of sodium acetate (88.1 ± 5.2% against 81.4 ± 4.5% and 96.9 ± 3.1% versus 91.5 ± 2.8%) due to greater key enzyme activity and short-cut nitrification and denitrification capacity. Finally, based on the actual operation process, an economic benefit analysis on the production of SCFAs-enriched fermentation liquid from UPOW was conducted, and the issues that need to be addressed for the promotion and application of this technology were discussed. This study contributes to achieving sustainable synergistic treatment of organic waste and wastewater. Full article

Cities increasingly face urban sustainability challenges due to rapid urbanization, climate pressures, and infrastructure demands. In response, smart city frameworks have emerged as transformative strategies that promote sustainability, efficiency, and resilience. Among the enabling technologies, the integration of the Internet of Things (IoT) and blockchain is gaining traction for supporting data-driven, transparent, and inclusive forms of sustainable smart cities. This systematic review analyzes peer-reviewed studies to examine how IoT and blockchain contribute to smart and sustainable urban development. The findings are organized into five thematic areas: (1) applications of IoT and blockchain for sustainable urban development; (2) operational applications across urban sustainability sectors such as energy, mobility, waste, and environmental management; (3) blockchain-enabled urban governance mechanisms including smart contracts, identity systems, and emergency response; (4) direct citizen engagement through transparent participation platforms and incentive-based systems; and (5) challenges and opportunities associated with IoT and blockchain technologies in the context of sustainable city development. In addition, the study proposes a conceptual framework that illustrates how IoT and blockchain integration support sustainable urban innovation. The review highlights the transformative potential of IoT–blockchain convergence in shaping future smart and sustainable cities and aligns with the United Nations Sustainable Development Goal 11. Full article

Biogas upgrading and bottling represent essential processes in transforming raw biogas produced via the anaerobic digestion of organic waste into high-purity biomethane (≥95% CH₄), a renewable energy source suitable for applications in cooking, transportation, and electricity generation. Upgrading technologies, such as membrane separation, pressure swing adsorption (PSA), water and chemical scrubbing, and emerging methods, like cryogenic distillation and supersonic separation, play a pivotal role in removing impurities like CO₂, H₂S, and moisture. Membrane and hybrid systems demonstrate high methane recovery (>99.5%) with low energy consumption, whereas chemical scrubbing offers superior gas purity but is limited by high operational complexity and cost. Challenges persist around material selection, safety standards, infrastructure limitations, and environmental impacts, particularly in rural and off-grid contexts. Bottled biogas, also known as bio-compressed natural gas (CNG), presents a clean, portable alternative to fossil fuels, contributing to energy equity, greenhouse gases (GHG) reduction, and rural development. The primary aim of this research is to critically analyze and review the current state of biogas upgrading and bottling systems, assess their technological maturity, identify performance optimization challenges, and evaluate their economic and environmental viability. The research gap identified in this study demonstrates that there is no comprehensive comparison of biogas upgrading technologies in terms of energy efficiency, price, scalability, and environmental impact. Few studies directly compare these technologies across various operational contexts (e.g., rural vs. urban, small vs. large scale). Additionally, the review outlines insights into how biogas can replace fossil fuels in transport, cooking, and electricity generation, contributing to decarbonization goals. Solutions should be promoted that reduce methane emissions, lower operational costs, and optimize resource use, aligning with climate targets. This synthesis highlights the technological diversity, critical barriers to scalability, and the need for robust policy mechanisms to accelerate the deployment of biogas upgrading solutions as a central component of a low-carbon, decentralized energy future. Full article

With the rapid development of urbanization, municipal waste incineration (MWI) has become the primary method of waste disposal in urban areas, leading to growing concerns about volatile organic compounds (VOC) emissions. This study conducted full-process VOC field sampling at a representative MWI plant in China to investigate the emission characteristics and removal efficiencies of air pollution control devices (APCDs). A total of 59 VOC species were identified in the flue gas, including 5 alkanes/alkenes, 14 aromatics, 8 oxygenated-VOCs, and 32 halogenated hydrocarbons. The activated carbon injection combined with fabric filters and wet desulfurization tower demonstrated varying removal efficiencies across VOC groups, with synergistic removal efficiencies being ranked as follows: alkanes/alkenes (90.9%) > aromatics (87.0%) > halogenated hydrocarbons (61.3%) > O-VOCs (42.2%). The total VOC removal efficiency reached 77.5%. The VOCs emission factor of the MWI plant was calculated as (1.9 ± 0.6) × 10³ ng/g-waste, which would rise to (8.4 ± 2.1) × 10³ ng/g-waste in the absence of APCDs. This indicates that the current APCD system reduces VOC emissions by approximately 6.52 × 10⁴ g annually from this MWI plant, highlighting the crucial role of multistage APCDs in mitigating VOC pollution. Full article

Municipal solid waste (MSW) management in Brazil faces significant challenges related to waste segregation, collection efficiency, and environmentally adequate disposal. This study quantifies the carbon emissions associated with organic solid waste management, from 2022 to 2034, in the city of João Pessoa (Northeast Brazil). To this end, the Life Cycle Assessment methodology is applied to two scenarios: Scenario 1 (where all organic fraction is landfilled) and Scenario 2 (progressive implementation of composting for the domestic organic waste, starting in 2023, with increases each year until reaching 50% in 2034, and the remainder being landfilled). The latter is proposed based on the targets established in the Municipal Solid Waste Plan of João Pessoa. Projection for MSW considered a per capita rate of 0.86 kg/inhab.day, combined with a population growth rate of 1.92%/year. The results indicate that Scenario 1 emits 825 Mt CO₂-eq while Scenario 2 emits 704 Mt CO₂-eq for the study period (a reduction of 15%). A sensitivity analysis examined the effects of increasing transport distance (25–45 km) and the organic fraction of MSW (35–45%) on GHG emissions. Although total emissions rose under both conditions, the comparative environmental advantage of composting over landfilling remained stable. These results confirm the robustness of the analysis and reinforce composting as a low-carbon, effective strategy for managing urban waste. Full article

A very important issue in urban agglomerations is the proper management of green waste while reducing its negative impact on the environment. One potential solution is the utilization of green biomass—originating from the maintenance of parks, squares, and home gardens—for the production of compost and compost-based pellets as organic fertilizers. The aim of this study was to produce compost-based pellets intended for fertilization purposes from compost derived from green waste and conifer sawdust, and to analyze their mechanical and chemical properties. Ten variants of pellets with different compost-to-sawdust ratios were evaluated. Compost-based pellets exhibited the highest initial mechanical strength; however, their resistance to external loads decreased over time, whereas the best long-term stability was observed in pellets containing 50% sawdust. The seasoning process influenced the stabilization or improvement of the mechanical properties of certain mixtures. Chemical analyses showed that compost-based pellets contained the highest concentrations of nutrients (N, P, K), while increasing the proportion of sawdust reduced their fertilizing value. No exceedances of permissible heavy metal limits were detected. The results confirm the suitability of compost-based pellets made from green biomass as a sustainable alternative to mineral fertilizers, supporting the principles of the circular economy. Full article

The intensification of agricultural practices and the consequent dramatic decrease in soil organic matter has increased the use of organic fertilizer to recover soil fertility and plant productivity. The aim of this study was to compare the effect of three amendments obtained from the recycling of urban and agri-food wastes on rhizosphere microbial community, soil, and plant nutrient status. The experiment was carried out on rhizobox-grown, 1-year-old vines of Sangiovese (Vitis vinifera L.), grafted onto 110 Richter (V. berlandieri × V. rupestris) planted in April 2023. Twenty-four rhizoboxes were filled with soil collected from a field trial in which three types of amendments had been applied since 2019. In detail, the complete randomized experimental design (with four replications) compared the following treatments: (1) municipal organic waste compost (ACM), (2) agri-food organic waste compost (ACF), (3) defecation gypsum (GDD), and (4) a control that received 60 kg of N ha⁻¹ year⁻¹ (CK). The application of the amendments increased the soil concentration of total C, total N, and pH. The application of ACM increases soil K and Zn and the concentration of N and K in plant roots. The application of all the amendments increased leaf N concentration in comparison with CK, but only ACF increased leaf P. ACM was the most effective in promoting microbial biodiversity, increasing phyla like Bacillota, Pseudomonata, and Bacteroidota, including genra like Bacillus, Neobacillus, Paenibacillus, and Pseudomonas. ACF promoted Nitrosospherota and Chitinophaga, and GDD promoted Chloroflexota and Agrobacterium. Full article

The soil condition of Norilsk, a large industrial city located in the Arctic zone of Russia, was assessed for the first time using pollution indices calculated based on the gross content of Pb, Zn, Co, Cd, Cu, Ni, Cr, Mn, As, and petroleum products. The Nemerov Pollution Index (NPI) classifies all Norilsk soil samples as polluted. According to the PLI index, 86% of the soil samples were characterized as polluted, and according to the total pollution index (Zc), 56% of the soil samples were classified as moderately hazardous and hazardous polluted. All soil samples had a medium, high, or very high environmental risk. The high level of soil pollution in Norilsk and the crucial role of nonferrous metallurgy as the primary source of these metals are confirmed. Pollutant content in the soil varied in different districts of Norilsk, with Mn and petroleum products being significant. The maximum heavy metal pollution occurred in the soils of the enterprise protection zones and in the soil of the industrial zones. Airborne pollutants from industrial enterprises are the main cause of heavy metal soil pollution in the Norilsk agglomeration. The contribution of other sources of pollution, typical for various functional areas of the city (e.g., motor transport and waste), is not expressed. Simultaneously, the hydrocarbon content is determined by the location of areas near roads, which is typical for districts with a high population and intensive traffic. Using the example of the Central District of Norilsk, the landscaping of the territory was shown to play a role in reducing the total content of heavy metals. Based on the physicochemical properties of Norilsk’s urban soils, the following key measures are proposed to improve soil quality: increasing organic matter content; ensuring a neutral pH and a high cation exchange capacity; and reducing soil density, which will reduce the toxic load on plants and negative impact on human health. Full article

In recent decades, the urban population of Ecuador has grown, increasing the need for wastewater sanitation in cities. Wastewater treatment in this country generates sewage sludge (SS), which is mainly deposited on land near wastewater treatment plants or in sanitary landfills, generating significant environmental impacts. In view of this, composting or vermicomposting of SS can be suitable treatments for this waste, and the final materials obtained can be used as organic amendments. The objective of this study was to compare the agronomic and economic aspects of composting and vermicomposting using the same SS mixtures with different plant residues. For this purpose, the evolution of various physicochemical and biological parameters of both processes, the quality of the materials obtained, and the costs of their production were evaluated. The results revealed that all the amendments presented characteristics suitable for safe agricultural use. The vermicomposts had significantly lower levels of salts and higher levels of most macro- and micronutrients than the composts, thus increasing their economic value. However, the average production cost of composts was lower than that of vermicomposts, with faster stabilization of organic matter. All of this indicates that both techniques could be suitable for treating SS, but in order to choose the most appropriate technique for the study area, further studies with other waste mixtures and agricultural validation of the composts and vermicomposts obtained, as well as control of possible contaminants, would be required. Full article

The sustainable management of urban grasslands is crucial for resilient city ecosystems. With increasing urbanization, improving soil quality to support turfgrass growth has become a priority. This study evaluates biochar produced from Paulownia leaves (PLB), a low-cost byproduct of Paulownia cultivation, as a growing medium amendment. Raw leaves (PL) and PLB were characterized by SEM, FTIR, and elemental analysis to assess physicochemical changes. A three-month pot experiment under outdoor conditions was conducted with turfgrass plots exposed to different irrigation and fertilization regimes. Growing medium pH, moisture, electrical conductivity, cation exchange capacity, nutrient availability, grass chlorophyll content, and uptake were monitored. The application of PLB improved the growing medium structure, raised the pH by up to one unit, and enhanced pigment accumulation in turfgrass samples. When combined with nitrogen fertilizer, PLB significantly increased turfgrass visual quality, whereas under limited irrigation, PLB alone improved seedling establishment compared to controls. Statistical analysis confirmed significant treatment effects by ANOVA, and PCA provided a precise classification of treatment groups. These findings indicate that PLB can improve nutrient efficiency, turfgrass resilience, and organic waste management. Full article

Enhancing plant nutrient use efficiency, yield, and quality without compromising sustainability remains a critical challenge in agriculture. Utilization of materials such as biowaste derivatives as alternatives to conventional agrochemicals (e.g., fertilizers, biostimulants) can be leveraged to optimize crop productivity and resilience while adhering to sustainable practices. A soluble bioproduct (BP), isolated from the hydrolysis of anaerobic digestates derived from organic residues of urban waste, was examined for its capacity to enhance tomato (Solanum lycopersicum) production and quality. Five basal fertilization treatments were applied: conventional (CF), conventional/organic (CF + OF), bioproduct at 150 kg ha⁻¹ (BP), and conventional/BP at 150 and 300 kg ha⁻¹ (CF + BP, CF + 2BP), without or with supplementary fertigation (SF). The experiment was arranged in a Randomized Complete Block Design. Intermediate plant growth under BP was comparable to CF, while their combination enhanced growth parameters. However, addition of BP to CF did not affect final plant growth, biomass, and yield compared to CF alone, though non-significant reductions of height (5.37%), leaf number (15.89%) and fresh weight (36.09%) were observed with BP alone. The same treatment reduced intermediate leaf macronutrients (N, K, Na), whereas this was ameliorated with CF + BP. The use of BP without fertigation enhanced final P content in leaves and roots. However, fruit P declined, reflecting delayed P availability and translocation. The use of BP induced plant stress responses, accompanied by stimulation of phenolic and antioxidant accumulation in leaves, with fruit exhibiting comparable increases only without fertigation. Fruit lycopene and total soluble solids were enhanced by CF + BP, with fertigation mediating differences. Combined CF and BP application promoted tomato fruit quality, without diminishing growth, while the performance of BP alone was improved with supplementary fertigation to maintain tomato growth, yield, and quality. Full article

Soil degradation and poor fertility severely constrain vegetation growth in urban ecosystems, particularly in compacted and nutrient-depleted tree pits. Mulching has emerged as an effective strategy to improve soil quality and regulate soil–microbe–plant interactions, yet the combined use of organic and inorganic mulching in urban landscapes remains underexplored. In this study, a one-year field experiment was conducted to evaluate the effects of four mulching treatments on soil bacterial community diversity and functional potential. Four treatments were applied green waste compost + wood chips (GW), green waste compost + wood chips + volcanic rocks (GWV), green waste compost + wood chips + pebbles (GWP), and a non-mulched control (CK). Organic mulching (GW) effectively reduced bulk density, enhanced cellulase and protease activities, increased bacterial community richness and balance, and enriched microbial genes associated with carbon and nitrogen metabolism, while organic–inorganic mulching further promoted soil nutrition and reshaped bacterial community structure. Soil pH, nitrogen content, and protease activity served as key drivers of bacterial community structure and function. These findings demonstrate that different mulching practices provide distinct ecological advantages, and together highlight the role of mulching in regulating soil–microbe–plant interactions and improving urban tree pit management. Full article