Search Results (601)

Carbon sequestration and emission reduction via biochar represent a promising approach for carbon storage. Continuously collected roadway fallen leaves serve as an attractive precursor for biochar-based carbon sequestration. However, the realistic carbon sequestration potential (derived from biochar production) of these urban waste resources remains poorly quantified and deserves further investigation. Against the backdrop of global sustainability goals, this study estimated the potential of using roadway fallen leaves for carbon sequestration at the urban scale of Hangzhou, based on government reports and pyrolysis experiments. Results indicated that there were a total of 691,472 roadway trees in Hangzhou. If the fallen leaves of the roadway trees in Hangzhou were subjected to oxygen-limited pyrolysis at a temperature of 300 °C for carbon sequestration purposes, the potential total carbon sequestration capacity was estimated to be 2273 ± 55 tons of carbon, equivalent to 8334 ± 200 tons of carbon dioxide. Leaf-derived biochar carbon sequestration index (LBCS) was established for potential use in the future Certified Emission Reduction (CCER). Different leaf types and pyrolysis conditions correspond to different LBCS values. LBCS for Camphor tree (300 °C) was 3.64 $\mathrm{kg} \mathrm{C}·{\mathrm{tree}}^{-1}{·\mathrm{year}}^{-1}$. Thermal maps of carbon sequestration potential of roadside leaf resources in 13 counties and districts of Hangzhou made by this study provided a reference for potential future practices. It was further estimated that with one-third of the tree leaves used for leaf-derived biochar (300 °C) carbon sequestration between 2027 and 2060, the cumulative carbon sequestration potential could reach up to 18.96 billion tons CO₂-eq by 2060, contributing 29–68% of the global GHGs emission reduction goal for bioenergy with carbon capture and storage (BECCS). We noted that this long-term cumulative estimate relied on linear extrapolation assumptions and contained uncertainties. This research offered new insights and quantitative baseline data for advancing negative-carbon technology using urban leaf waste, supporting local waste recycling practices and the urban implementation of the United Nations 2030 Agenda toward carbon-neutrality objectives. Full article

Urban waterfront spaces that are ecologically sensitive often remain visually prominent yet inaccessible, posing a management challenge: how to generate public engagement and economic value without physical access. This paper proposes a four-stage socio-ecological framework integrating sensory restoration, behavioral transformation, economic generation, and ecological reinvestment. Using Xianyang Lake in China as a demonstrative case, the study applies six years of phenological records from 36 plant species. Analytic hierarchy process and k-means clustering derive four seasonal sensory palettes, ensuring year-round visual, olfactory, and auditory engagement. A proposed WeChat-based guidance system illustrates how passive sensory exposure could be converted into active behavioral engagement across walking, bridge viewing, and boating. The framework links enhanced experience to a dynamic revenue model and closes the loop by reinvesting proceeds into maintenance and sediment reuse for greenbelt expansion. The empirical component consists of phenological data analysis and seasonal palette derivation, while the socio-economic pathways are presented as testable hypotheses requiring future empirical validation. The findings shift the paradigm from physical to sensory accessibility, offering a conceptually transferable framework for managing inaccessible urban blue-green spaces. Full article

Waste accumulation and land carrying pressure are common sustainability challenges in urbanization, making the improvement of urban land green use efficiency (ULGUE) a key issue. Using panel data from 278 Chinese cities over 2008–2023, this study treats zero-waste city pilots as a quasi-natural experiment and constructs a difference-in-differences model, measuring ULGUE via a super-efficiency slacks-based measure–Global Malmquist–Luenberger (Super-SBM-GML) model under variable returns to scale. The results show that zero-waste city construction significantly and robustly improves ULGUE. Mechanism analysis shows that zero-waste city construction improves ULGUE mainly by optimizing the waste treatment structure, promoting green technological innovation, and facilitating the development of green industries. Heterogeneity analysis shows that the promoting effect is stronger in eastern regions, key environmental protection cities, old industrial base cities, and resource-based cities. Moderating effect analysis indicates that rising public environmental attention and internet development strengthen this effect. Spatial econometric analysis further shows that zero-waste city construction generates significant positive spatial spillovers on neighboring regions in addition to improving local ULGUE. This study reveals the underlying logic and micro-level transmission paths of zero-waste city policy, situates China’s experience within global circular economy governance, and offers policy evidence for emerging economies advancing green land use. Full article

Waste from the aggregate processing industry has the potential to be used for value-added products. Its plastic properties and sinterability allow for the production of lightweight aggregates. This process can yield materials with high open porosity at various scales. This article presents the possibilities of obtaining lightweight aggregates from clay–silt fractions obtained by washing crushed dolomite aggregates. Aggregate formation was achieved using selected mechanical processing methods, such as dynamic granulation, sedimentation, crushing, and classification. Biomass was added to increase the aggregate’s porosity. The following instrumental techniques were used to assess the aggregate’s parameters: X-ray fluorescence (XRF) to obtain detailed information on the oxide composition of the tested raw materials; high-temperature microscopy (HSM) to determine the specific sintering temperature; and pH and conductivity meters to examine filtration solutions in direct contact with the aggregate. A key issue was to examine the microstructure of the produced aggregates after firing using scanning electron microscopy (SEM), Brunauer–Emmett–Teller method for measuring material surface area (BET), and X-ray diffraction (XRD) technique. The obtained results will allow for further research into developing a concept for the production of lightweight alkaline aggregates. The aggregates produced exhibit high water absorption (approximately 50%), a low bulk density of 0.82 g/cm³, and meso- (approximately 30–100 µm) and bioporosity (approximately 100–500 µm), which is beneficial for the proper development of plant roots and the absorption and release of water. This research contributes to the identification of resources that can be transformed into lightweight aggregates for urban greening, which is consistent with circular economy strategies and environmental protection. The specific mechanisms through which this research supports sustainable development are the reduction in landfill sites and the protection of natural resources. Furthermore, the aggregates produced can form part of blue-green urban infrastructure, which aims to manage rainwater and reduce the urban heat island effect. Full article

Population growth in urban food systems has led to a decline in food resources and the emergence of social imbalances, while consumers’ shift toward a healthy and sustainable lifestyle, against the backdrop of a growing carbon footprint and negative health impacts, highlights the need to promote fish-based products as part of a balanced diet, alongside the implementation of circular strategies for utilizing byproducts from processing, which has led to increased interest in reformulating these products in accordance with the principles of the circular bioeconomy. Aquaculture and the agri-food industry generate a large amount of byproducts that are underutilized, even though they could be extremely useful as functional food ingredients. Recycling these streams into ingredients is an effective way to reduce food waste, make better use of resources, and lessen the environmental impact of food systems. In this context, by-products can be strategically incorporated into food reformulation processes, where their bioactive compounds simultaneously improve both the nutritional value and the technological function of foods. However, such approaches can only be effectively utilized if there is a coordinated framework that ensures food safety, supports scalable processing technologies, and complies with regulatory standards. This analysis takes an integrated approach to examine how specific processing strategies, quality control measures, and risk assessment protocols can work together to ensure nutritional optimization, guarantee food safety, and promote circular use. This paper also addresses how these interconnected systems contribute to maintaining public health and increasing consumer confidence, particularly in urban food systems. By highlighting these connections, the research offers a clearer operational perspective on applying circular economy principles to sustainable food production. Even with these opportunities, issues related to scalability, regulatory compliance, and the limited number of applied studies remain major challenges. In this context, this paper examines how the coordinated implementation of these mechanisms can contribute to public health, strengthen consumer confidence, and facilitate the transition to sustainable urban food systems. Finally, this paper offers a clearer operational perspective on how the principles of the circular economy can be effectively put into practice by harmonizing nutrition, safety, and value-added recovery. Full article

The growing pressure of municipal waste generation and its associated environmental consequences has turned household participation into a central challenge for sustainable waste governance and circular-economy transition. This study adopts Cultural Additivity Theory and employs Bayesian Mindsponge Framework (BMF) analytics to examine how interactions between environmental–cultural and governance value bundles shape household willingness to pay (WTP) for improved urban waste management services, using survey data from 352 households in Hai Phong City, Vietnam. The results show that both the perceived importance of Commune Authorities and Women’s Unions are positively associated with WTP. More importantly, environmental perception and behavior further strengthen these governance–WTP associations, indicating that household financial support for improved waste management is greater when governance values interact with stronger environmental–cultural values. In contrast, higher environmental service satisfaction tends to weaken the positive association between governance importance and WTP. These findings suggest that household WTP is better understood as a relational outcome of interacting value bundles rather than as the product of isolated determinants operating independently. This study makes three contributions. First, it extends Cultural Additivity Theory into the field of urban environmental governance by demonstrating how interactions among value bundles shape household environmental decision-making. Second, it advances the waste-management literature by showing that environmental perception and environmental behavior become more influential when embedded within supportive governance and community structures. Third, it provides empirical evidence for developing community-based urban waste-management policies that integrate environmental communication, source-separation initiatives, local governance, and women-led community engagement to strengthen public participation and support sustainable urban waste-management systems. Full article

Hydrochars (HCs) were produced from pine needles (urban waste), brewer’s spent grain, and grape pomace via hydrothermal carbonization (HTC) at 230 °C, and were comparatively assessed as unmodified, low-dose amendments (1 wt%) in an alkaline soil slurry. Fixed-contact-time (4 h) batch tests were conducted using a Taguchi L9 array to screen the effects of feedstock type, HTC residence time, initial metal concentration, and test temperature on the aqueous-phase removal of for Zn, Pb, and Cd at this fixed endpoint. In the ternary test containing 20 mg/L of each metal, the soil-only control removed 94% Zn, 99% Pb, and 96% Cd, whereas the soil amended with 1 wt% pine-needle HC removed 98% Zn and 99% Pb, while Cd in the recovered liquid was below the instrumental detection limit. Operational distribution coefficients (K_d) and separation factors (SF) calculated at the 4 h endpoint indicated preferential Cd partitioning within the amended soil system. These findings support further evaluation of minimally processed, low-dose hydrochars for metal-contaminated soils, while providing a potential valorization route for residual biomass within a circular economy framework. Full article

This study investigates how integrated smart urban systems enhance resource efficiency in Saudi Arabia’s rapidly urbanising cities. Despite growing global interest in smart cities, there remains a critical gap in empirical research that simultaneously examines smart energy, water, and waste systems within a unified analytical framework, particularly in emerging urban contexts, while the mediating role of governance efficiency remains underexplored. Adopting a quantitative survey design, this study employs Structural Equation Modelling (SEM) to analyse 384 valid data from 384 stakeholders across selected urban areas. A stratified sampling approach ensures representation of policymakers, urban planners, and infrastructure managers, and measurement constructs are adapted from validated scales to ensure reliability and validity. The study examines relationships between smart energy systems, smart water management, smart waste monitoring, governance efficiency, and resource efficiency outcomes, with governance efficiency conceptualised as a mediating variable enhancing the effectiveness of smart urban systems. The study hypothesises that integrated smart technologies significantly improve resource efficiency, with smart infrastructure as a key predictor; structural model robustness is assessed using standard SEM fit indices, with CFI (0.93), TLI (0.91), and RMSEA (0.052). This research contributes to theory by integrating smart urban systems and governance into a unified framework, extending smart city and circular economy literature, while offering practical insights aligned with Saudi Vision 2030 to support sustainable urban development. It is recommended that policymakers prioritise integrated smart infrastructure, strengthen institutional frameworks, and promote public awareness to maximise resource optimisation. Future research should adopt longitudinal designs, expand across multiple cities, and incorporate behavioural and policy variables to enhance generalizability and deepen insights into smart urban resource efficiency. Full article

Municipal sludge generation has increased rapidly with urbanization, creating significant challenges for sustainable waste management. This review proposes a system-oriented framework for sludge resource utilization by linking sludge characteristics, conversion technologies, environmental risks, and product applications. Major treatment pathways, including anaerobic digestion, pyrolysis, ozonation, and hydrothermal carbonization, are critically compared, with emphasis on their inherent trade-offs between resource recovery, energy consumption, and contaminant control. Particular attention is given to emerging contaminants, such as microplastics, per- and polyfluoroalkyl substances (PFAS), and antibiotic resistance genes, where the distinction between pollutant removal and actual risk reduction remains insufficiently addressed. The review highlights that no single technology can achieve optimal performance under all conditions, and integrated treatment trains are generally required for sustainable sludge management. Among these pathways, pyrolysis shows considerable potential for applications requiring enhanced contaminant control and value-added biochar production due to its ability to promote organic contaminant degradation, heavy metal immobilization, and carbon storage. However, the feasibility of pyrolysis and other technologies depends strongly on site-specific factors, including sludge properties, energy availability, economic conditions, and regulatory requirements. Future research should focus on integrated process optimization, comprehensive pollutant fate assessment, and standardized evaluation frameworks to advance sludge management toward a circular economy. Full article

Organic amendments derived from agro-livestock residues offer a promising approach for soil restoration and nutrient recycling within circular economy frameworks. Nevertheless, their agronomic efficacy and environmental suitability may be contingent upon the formulation of the amendments and the properties of the soil. This study presents a preliminary evaluation of customized organic amendments derived from solid materials, such as biochar and green compost, and liquid residues, including cattle manure slurry, urban compost tea, and cattle digestate. These were applied either individually or as solid–liquid mixtures to two distinct Iberian soils. The study involved amendment characterization, seed germination assays, and a two-month greenhouse experiment with barley (Hordeum vulgare L.) to assess the effects on soil physicochemical properties, microbial activity, and plant development. The solid–liquid impregnation process facilitated the transfer of nutrients and potentially limiting elements from liquid residues to solid matrices, thereby altering amendment composition and mitigating some risks associated with the direct application of liquid residues. Mixtures based on biochar and compost generally alleviated excessive salinity and trace metal constraints, although responses varied depending on the liquid amendment and soil type. Biochar-containing amendments markedly increased soil total carbon, suggesting their potential to contribute to soil carbon sequestration. The effects of amendments were strongly dependent on soil type: acidic soil exhibited more pronounced pH improvement, whereas the carbonate-rich alkaline soil buffered several chemical changes but was more susceptible to alkalinization and sodium inputs. Urban compost tea consistently exhibited inhibitory effects on germination, plant development, and dehydrogenase activity, although these effects were partially mitigated when combined with solid amendments. Overall, the findings underscore the potential of tailored amendment mixtures to enhance residue valorisation, while highlighting the necessity for soil-specific evaluation prior to field application. Full article

Activated carbon is a highly porous adsorbent material that is often used to treat wastewater using physical and chemical adsorption. Agricultural and urban biomass waste valorization to activated carbon is a low-cost, renewable solution to commercial adsorbents, and can help prevent waste from tree pruning from being dumped in landfills or openly burned. In this study, the ability of the ground and unground Ficus nitida leaves to efficiently adsorb Rhodamine B dye and total chromium from model aqueous solutions was investigated. Chemical activation was performed using phosphoric acid (H₃PO₄) at different impregnation ratios (1:1, 2:1, and 4:1). Samples obtained as a result of the above activation were labeled G1–G3 (ground) and UG1–UG3 (unground). The adsorption test showed that the samples with the highest activation ratio (G3 and UG3) gave the best results, removing 92% and 94% RhB, respectively, in 20 minutes. After 24 h, sample G3 showed the best efficiency of 73.31% (13.35 ppm remaining) in chromium removal, where the adsorption kinetics were well described by the pseudo-second-order model (R² > 0.98), indicating that there may be some chemical interactions occurring during the adsorption process along with physisorption, and the RhB adsorption isotherms for sample UG3 were well described by the Langmuir isotherm (R² > 0.95). The higher activation ratio and grinding increased the carbon content (up to 90% C for G3), surface functional groups, and textural properties (BET surface area of 699 m²/g and total pore volume of 3.06 cm³/g). Furthermore, reusability tests over five consecutive cycles demonstrated the excellent recyclability of sample G3, retaining removal efficiencies of 80.5% for RhB and 50.2% for total chromium. The results revealed that Ficus nitida leaf-based AC can be used as an efficient, economical, and reusable adsorbent material for sustainable environmental cleanup and water purification systems and will create a circular economy for waste management. Full article

Urban and industrial activities have lasting effects on Earth ecosystems, impairing their functionality. Technosols offer a sustainable solution for restoring degraded urban and industrial ecosystems. In a 30-day microcosm experiment, a mixture of six pioneer plant species was sown in three substrates: a sewage sludge-based Technosol (GF), a zeolite-enriched Technosol (GZ), and a commercial potting mix control (GC). The plant population dynamics, final performance, and substrate biochemical properties were monitored. A strong environmental filter allowed only two species (Bromus inermis Leyss. and Lolium perenne L.) to establish. Technosols exerted a demographic bottleneck, delaying emergence and reducing the total biomass relative to the control. Zeolites in the GZ Technosol mitigated this delay, accelerating early establishment due to their microporous structure and high cation exchange capacity. However, GZ caused the greatest reduction in individual biomass and functional plant performance index, corresponding to a microbial shift toward oxidative activity at the expense of hydrolytic nutrient mineralization. These results show that sewage sludge Technosols can initiate functional ecological succession. While zeolites positively affect germination, their microbial interaction suggests a temporary decoupling between the establishment speed and final productivity. Integrated monitoring of demographic and biochemical dynamics is therefore essential to optimize Technosol-based environmental restoration. Full article

Rapid population growth, urbanization, and industrialization are continuously increasing global energy demand while intensifying climate change associated with fossil fuel consumption. In this context, renewable energy production from organic waste has gained increasing attention as a sustainable and environmentally friendly strategy. Anaerobic digestion (AD) offers significant potential for simultaneous waste stabilization and biomethane generation. However, many previous studies investigating lignocellulosic or nutrient-rich substrates have relied on physical, chemical, or thermal pretreatment methods to enhance biodegradability, despite their additional operational costs, energy consumption, and environmental impacts. Therefore, developing low-cost and pretreatment-free co-digestion strategies remains an important research need. This study investigated the biomethane production potentials of untreated chicken manure (CM) and duckweed (Lemna minor-LM) collected from the final sedimentation tanks of wastewater treatment plants under mono-digestion and co-digestion conditions. The study hypothesized that rapidly growing and widely available LM biomass could enhance methane production without requiring pretreatment. Among all reactors, CM0.75 (75% of the total TS derived from CM and 25% from LM and inoculum) achieved the highest performance with a cumulative biogas production of 5350 mL (74.2% of CH4) and a methane yield of 327 mL CH4/g VS, while mono-digestion of CM resulted in the lowest methane yield of 104 mL CH4/g VS. The results demonstrated that LM biomass naturally proliferating in wastewater treatment plants can be directly utilized as an effective co-substrate to improve biomethane production from poultry wastes. The proposed approach provides a cost-efficient, eco-friendly, and circular-economy-oriented alternative by eliminating the need for pretreatment while simultaneously valorizing problematic biomass generated in wastewater treatment facilities. Full article

The 1st International Online Conference on Environments addresses issues of environmental understanding, management, and restoration. Sessions ranged from general frameworks to a broad area of specific investigations: heavy metal removal using inactive yeast, gadolinium’s aquatic toxicity, adsorptive removal of pollutants, energy recovery from waste and wastewater treatment, recycled carbon fibers, climate-resilient urban development, renewable biofuel production, green hydrogen, anthropogenic and volcanic CO₂ emissions, quantifying aging dignity in urban ecosystems and stray dogs as pollution health sentinels. Keynotes covered digital plant phenotyping for restoration, microplastic dynamics, agricultural residue management, carbon credits, air quality, atmospheric pollution, transitional waters, green chemistry, ecotoxicity, micropollutants, and coastal darkening effects on plankton, among others. Applied solutions included phytoremediation of eutrophication in urban streams, circular approaches in aquaculture, biochar for wastewater treatment, AI-assisted mangrove monitoring, and true-cost accounting for food systems. The conference demonstrated that effective environmental policy requires the integration of laboratory findings, field restoration, and shared resource responsibility across terrestrial and marine ecosystems. Full article

Historic urban manufacturing territories are increasingly being reconsidered as strategic components of metropolitan sustainability rather than obsolete remnants of industrial economies slated for redevelopment. While these districts have long been associated with pollution, environmental degradation, and post-industrial decline, growing interest in circular economy strategies, Urban Resource Recovery (URR), and climate adaptation has renewed attention to their territorial significance. Using the North Brooklyn Industrial Business Zone and the Newtown Creek watershed as a case study, this paper argues that certain historic manufacturing territories possess an inherent capacity to evolve into Metropolitan Metabolic Infrastructure because of inherited geographic, infrastructural, and institutional characteristics, including waterfront access, freight networks, industrial zoning, large industrial parcels, and utility systems. Drawing upon research developed through the New York City Department of Design and Construction’s Town+Gown Urban Resource Recovery Working Group, the study combines historical analysis, spatial interpretation, planning policy, and case-study research to examine the evolving relationship among urban metabolism, circular economy, environmental justice, and Healthy Cities. Rather than advocating industrial preservation irrespective of environmental performance, the paper argues that these territories can support metropolitan material circulation while advancing cleaner industrial practices, environmental remediation, and more equitable urban development. The Metropolitan Metabolic Infrastructure framework offers a planning perspective for understanding how inherited manufacturing landscapes may contribute to resilient, circular, and healthier metropolitan regions while informing future comparative research on industrial territories undergoing similar transitions worldwide. Full article