Search Results (371)

Tourism-driven growth in Zanzibar has intensified solid waste generation, creating critical environmental and resource management challenges for the hotel sector. This study provides the first comprehensive assessment of the volume, composition, and management of solid waste in Zanzibar’s hotels, establishing a quantitative basis for evidence-based sustainable practices beyond prior research on food waste. Ten hotels were examined through direct waste sampling, structured interviews, and field observations. Results show that hotels generate high levels of unsorted waste (2.45 kg/guest/day), with plastics posing major challenges under the prevailing linear disposal system. Findings reveal that waste patterns depend primarily on management, service, and collection practices, with no significant differences across hotel types or sizes. While the assessment covered the entire waste stream, a tailored circular economy framework is proposed for plastic waste, given its significant contribution to environmental pollution and ecological impact, providing a practical, structured guide for sustainable interventions across hotel operations. Achieving these outcomes requires collaboration, institutional support, and capacity building. By embedding waste audits, reduction strategies, and circular innovations into hotel operations, this framework charts a forward-looking pathway for coastal destinations to transform waste challenges into opportunities, promoting sustainable tourism, resource-use efficiency, and the transition toward a circular economy. Full article

The municipal solid waste recycling industry has become a rapidly growing emerging industry. Its carbon emissions account for 1/10 of the urban carbon emissions, which cannot be ignored. It is highly important for cities to achieve the goals of peak carbon and carbon neutrality and to strive for space for economic and social development. Taking Beijing as an example, using the life cycle analysis method, this paper systematically combines the historical changes in the characteristic structure of municipal solid waste. On this basis, the amount and structural characteristics of carbon emissions and their evolution are calculated, the achievements of municipal solid waste treatment in Beijing are comprehensively evaluated, and the space for further emission reduction in the future is estimated. The following conclusions are drawn: (1). Since the implementation of waste classification treatment, carbon emissions in Beijing have decreased by 22.9%. (2). Carbon emissions from plastic and paper waste from municipal solid waste have become the main source of carbon emissions from waste treatment. (3). There is still more than 2.6 × 10⁶ t of carbon emission reduction space for municipal solid waste treatment in Beijing in the future. On the basis of the calculation results, several suggestions are proposed. Full article

Expansive clay soils present major challenges for infrastructure due to their high swelling potential and low bearing capacity. While conventional stabilisers, such as lime and Ordinary Portland Cement (OPC), are effective, they are environmentally unsustainable due to their high carbon footprint. This study examines the potential of shredded recycled polyethene terephthalate (PET) fibres as a low-carbon alternative for stabilising high-plasticity clays. PET fibres were incorporated at dosages ranging from 0% to 1.2% by dry weight, and their influence on compaction characteristics, unconfined compressive strength (UCS), California Bearing Ratio (CBR), swelling behaviour, and microstructure was evaluated through laboratory testing and Scanning Electron Microscopy (SEM). Among the tested mixes, the 1.0% PET content exhibited the highest measured performance, resulting in a 37% increase in UCS, a 125% enhancement in unsoaked CBR, more than a two-fold increase in soaked CBR, and a 15% reduction in the Differential Free Swell Index (DFSI). SEM analysis indicated the formation of a three-dimensional fibre matrix, which improved particle interlock and reduced microcrack propagation. However, higher fibre dosages caused agglomeration and macrovoid formation, which adversely affected performance. Overall, the findings suggest that the inclusion of PET fibres can enhance both geotechnical and environmental performance, providing a sustainable stabilisation strategy that utilises plastic waste while reducing reliance on OPC. Full article

Polyethylene terephthalate (PET) is one of the most widely used plastics globally, and its poor post-consumer management poses serious risks to the environment and human health. Tackling this issue requires innovative strategies that combine recycling and sustainable manufacturing with the principles of the circular economy. This study addresses this challenge by investigating the use of recycled PET, along with reverse logistics, to produce a cell phone holder through additive manufacturing (AM). Characterization was performed using differential scanning calorimetry, thermogravimetric analysis, intrinsic viscosity measurements, and mechanical tensile tests. Environmental and circular performance were evaluated using Life Cycle Assessment (LCA) and the Material Circularity Indicator (MCI), comparing production with 100% virgin PET resin and 100% recycled PET resin. The results showed that the recycled route achieved a tensile strength of 37.7 MPa, with 7.6% strain before rupture, and thermal analysis confirmed its stability during processing. The LCA revealed a 12% reduction in overall environmental impacts when recycled PET replaced virgin resin, with electricity consumption identified as the main critical point. The circularity assessment suggested potential savings of up to 70% if recycled PET products are reprocessed at the end of their life cycles. These findings demonstrate that combining open-loop recycling with additive manufacturing (AM) can effectively turn waste into high-quality, value-added products, advancing circularity and sustainable material innovation. Full article

Calcined and acid-leached kaolin impregnated with Fe(NO₃)₃·9H₂O (6.6 wt. % Fe₂O₃) was developed as an inexpensive bifunctional catalyst for the slow fixed-bed pyrolysis of polypropylene (PP) and low-density polyethylene (LDPE). Experiments were run with catalyst-to-plastic mass ratios of 1:4, 1:2, and 1:1 in a quartz tube reactor heated from 25 to 800 °C. For PP, increasing the Fe/kaolin loading progressively raised non-condensable gas from 26 wt. % to 44 wt. % and drove liquid aromatics from 27.9% to 72.3%, while combined paraffins olefins fell to 2.5% and wax exhibited a 46 → 24 → 36 wt. % trend. In contrast, LDPE at a 1:4 ratio already yielded 56 wt. % oil and only 22 wt. % wax; further catalyst addition mainly enhanced CH₄/CO-rich pyrolysis gas (PyGas) and char without substantially boosting aromatics. Gas analysis confirmed that Fe₂O₃ reduction and kaolin de-hydroxylation generated in situ H₂O, CO, and H₂. Given the catalyst’s low cost, regenerability, and ability to valorize the two most abundant waste polyolefins within the same reactor, the process offers a scalable route to flexible fuel and gas production from mixed plastic streams. Full article

To address the challenges associated with Ordinary Portland Cement (OPC) in mine backfilling, including high costs, the large carbon footprint, and performance limitations, a novel cementitious powder (CP) based on alkali-activated slag is developed in this work. The mechanical performance and microstructural strengthening mechanism of this CP as a substitute for OPC in cemented copper tailing backfill (CTB) were systematically evaluated. The effects of key parameters, including the solid content (SC), tailing-to-cement ratio (TCR), and curing age (CA), were investigated using uniaxial compressive strength (UCS) tests and scanning electron microscopy (SEM) analysis. The results demonstrate that the novel binder exhibits superior performance. At a solid content of 73%, the CTB prepared with CP at a TCR of 10 or 12 achieved a compressive strength comparable to or exceeding that of the OPC-based counterpart with a TCR of 8. This represents a 33% reduction in binder dosage without sacrificing performance. The UCS of the CTB increased significantly with a decreasing TCR and an increasing CA, with the most rapid strength development observed during the early curing stages (≤7 days). The stress–strain behavior transitioned from plastic yielding to strain-softening with prolonged curing, and the macroscopic failure was predominantly governed by tensile cracking. Microstructural analysis revealed that the strength development of the CTB originates from the continuous formation of hydration products, such as calcium-silicate-hydrate (C-S-H) gel and ettringite. These products progressively fill pores and encapsulate tailing particles, creating a dense and interlocking skeletal structure. A lower TCR and a longer CA promote the formation of a more integrated and compact micro-network, thereby enhancing the macroscopic mechanical strength. This study confirms the viability of the slag-based binder as a sustainable alternative to OPC in mining backfill applications, providing a critical theoretical basis and technical support for the low-cost, eco-friendly utilization of mining solid waste. Full article

Plastic waste accumulation poses a critical environmental challenge, while the road construction industry continues to rely heavily on energy intensive, non-renewable binders. Integrating waste plastics into asphalt offers a dual solution to these issues by enhancing pavement performance and promoting circular economy principles. This review provides a comprehensive and data-driven synthesis of global research on plastic-waste-modified asphalt (PWMA), covering six major plastic types and both wet- and dry-processing technologies. Unlike prior reviews, this study employs a systematic PRISMA-based selection framework to evaluate 42 peer-reviewed experimental studies from 2000 to 2024, quantitatively comparing rheological, mechanical, and environmental outcomes. The review identifies polymer bitumen compatibility mechanisms, microstructural interactions revealed through microscopy, and the role of pre-treatment processes (glycolysis and pyrolysis) in improving dispersion and stability. Life Cycle Assessment (LCA) data reveal 20–35% reductions in carbon emissions and 10–12% life cycle cost savings compared to conventional and SBS-modified asphalt. The review proposes a strategic roadmap addressing performance variability, microplastic emissions, and compatibility challenges. By integrating material science, sustainability assessment, and field implementation data, this review advances a novel multidisciplinary perspective on waste plastic valorization in road infrastructure, bridging the gap between laboratory research and policy-ready, scalable applications. Full article

This study experimentally and numerically examines the structural and seismic performance of recycled solid-brick masonry infills and load-bearing walls constructed from demolition materials. Solid bricks recovered from demolished structures were reused as infill in reinforced concrete (RC) frames and as standalone walls. Five full-scale panels, bare, 50% infilled, and 100% infilled frames, were tested under diagonal compression in accordance with ASTM E519-17, simulating in-plane seismic loading. Results showed that fully infilled frames exhibited a 149% increase in diagonal shear strength but a 40% reduction in ductility relative to the bare frame, indicating a trade-off between stiffness and deformation capacity. Finite element simulations using the Concrete Damaged Plasticity (CDP) model reproduced the experimental load–displacement curves with close agreement (within 6–8% in peak load) and captured the main failure patterns. Reusing cleaned demolition bricks reduces the demand for new fired bricks and helps divert construction waste from landfill, contributing to sustainable and circular construction. The findings confirm the potential of recycled masonry for low-carbon and seismic-resilient construction, provided that ductility limitations are appropriately addressed in design. Full article

This work investigated the use of microbial fuel cells (MFCs) for the degradation of polyethylene terephthalate (PET) and the simultaneous generation of electricity. The study implemented two separate single-chamber MFCs, one with a co-culture of Ideonella sakaiensis and Geobacter sulfurreducens (I.S-G.S) and the other with Ideonella sakaiensis and activated sludge (I.S-AS). The effectiveness of microplastic (MP) degradation was assessed based on the electroactivity of the anodic biofilm, the reduction in particle size, and the decrease in PET mass. Both systems achieved a significant reduction in MP size and mass, with the I.S-AS system notably surpassing the I.S-G.S in terms of efficiency and electricity generation. The I.S-AS system achieved a 30% mass reduction and 80% size reduction, along with a peak voltage of 222 mV. The study concludes that MFCs, particularly with the activated sludge co-culture, offer a viable and more environmentally friendly alternative for MP degradation and energy recovery. These findings suggest a promising direction for improving waste management practices and advancing the capabilities of bio-electrochemical systems in addressing plastic pollution. Further research is recommended to optimize the operational conditions and to test a broader range of MP sizes for enhanced degradation efficacy. Full article

This study examines the effectiveness of pervious concrete pavements as a sustainable and cost-effective stormwater management technique, particularly by incorporating locally sourced recycled materials into their design. It evaluates the stormwater treatment potential of three pervious concrete pavement types incorporating recycled plastic, glass, and crushed concrete aggregates, with six design variations produced using 25% and 50% replacements of coarse aggregates from these materials. The key properties of pervious concrete, namely compressive strength, porosity, unit weight, and infiltration, and key water quality indicators, namely pH, electrical conductivity (EC), total suspended solids (TSS), colour, turbidity, chemical oxygen demand (COD), nitrate (NO₃⁻), and orthophosphate (PO₄³⁻), were analysed. Results indicated an overall improvement in the quality of the stormwater runoff passed through all pervious concrete pavements irrespective of composition. Notable reductions in turbidity, TSS, colour, COD, PO₄³⁻, and NO₃⁻ underscored the effectiveness of pervious concrete containing waste materials in the treatment of stormwater runoff. Pervious concrete pavements with 25% recycled concrete exhibited optimal performance in reducing TSS, COD, and PO₄³⁻ levels, while the 50% recycled concrete variant excelled in diminishing turbidity. However, the study found that the use of recycled materials in pervious concrete pavements affects properties like compressive strength and infiltration rate differently. While incorporating 25% and 50% recycled concrete aggregates did not significantly reduce compressive strength, the effectiveness of stormwater treatment varied based on the mix design and type of recycled material used. Thus, this study highlights the potential of utilizing recycled waste materials in pervious concrete pavements for sustainable stormwater management. Full article

Plastics are inexpensive and widely used but persist in the environment due to improper disposal. Insect-mediated biodegradation has gained attention, notably involving Tenebrio molitor larvae. Despite morphological similarities and larger size, Zophobas atratus larvae remain less studied. This work evaluated the impact of larval stage on the biodegradation of pristine and post-consumer extruded polystyrene (XPS) and the physiological effects of an XPS-based diet. Smaller (L1) and larger (L2) larvae were tested. L2 showed higher XPS consumption, weight gain, and survival, while XPS-fed larvae overall exhibited reduced lipid content and increased moisture, flavonoids, and phenolics compared to wheat bran-fed controls. Scanning electron microscopy revealed surface fragmentation in frass, more pronounced in L1, suggesting greater mechanical or enzymatic action. High-performance size exclusion chromatography indicated molecular weight reduction, with L1 more effective on pristine XPS and L2 on post-consumer XPS, likely due to nutritional residues. FTIR analysis showed oxidative changes in both groups, more prominent in L1. Thermogravimetric analysis revealed earlier degradation onset in L1 frass, supporting the presence of oxidized oligomers. Overall, Z. atratus larvae can biodegrade XPS, with degradation influenced by developmental stage and substrate type. These findings inform biotechnological strategies for sustainable plastic waste management. Full article

Climate change is one of the most pressing global environmental challenges, driven by the accumulation of greenhouse gases in the atmosphere. Industrial processes, particularly plastic injection molding, are major contributors due to their high energy demand, raw material use, and waste generation. This study quantifies the carbon footprint of plastic injection molding operations and identifies emission hotspots to support alignment with sustainability objectives. A greenhouse gas inventory was developed for the production processes of Petka Mold Industry in Adana, Türkiye, covering 1 January–31 December 2023. The assessment followed the ISO 14064-1:2019 standard and included emissions from direct fuel consumption, purchased electricity, refrigerant leaks, company vehicles, employee commuting, business travel, purchased goods, and waste transportation. Carbon dioxide, methane, and nitrous oxide were calculated in carbon dioxide equivalent units. This research represents the first comprehensive carbon footprint study in the plastic mold sector integrating all categories (Categories 1–6). In addition, uncertainty and materiality analyses were applied to ensure robustness and transparency, an approach rarely adopted in similar industrial contexts. While most previous studies are limited to Categories 1–3, this work expands the boundaries to all categories, offering a pioneering model for industrial applications. The total corporate GHG emissions for 2023 were calculated as 3922.75 metric tons of CO₂e. Among the categories, purchased raw materials and end-of-life product stages were the most significant contributors, whereas transport and auxiliary services had smaller shares. The results provide a reliable baseline for developing action plans and pursuing emission reduction targets. By combining full category coverage with rigorous assessment tools, this study contributes methodological novelty to corporate carbon accounting and establishes a foundation for future progress toward carbon neutrality. Full article

The cement industry accounts for approximately 7% of global CO₂ emissions, with fuel combustion contributing 40% of sectoral emissions. Alternative fuels from industrial and municipal waste offer emission reduction opportunities while addressing waste management challenges. This study quantifies real-time gaseous emissions (CO₂, CO, NO_x, and SO₂) from seven alternative fuels—sawdust (SD), pecan nutshell (PNS), wind blade waste (WBW), industrial hose waste (IHW), tire-derived fuel (TDF), plastic waste (PW), and automotive shredder residue (ASR)—during calcination at 850 °C. Bituminous coal served as the reference fuel. Gas concentrations were continuously monitored using the testo 350 portable gas analyzer. Emission factors were calculated on a mass basis (kg/kg fuel) and energy basis (kg/GJ) for standardized comparisons. Alternative fuels consistently produced lower CO₂ emission factors than coal, with biomass-derived fuels (SD and PNS) showing reductions of 45% and 38%, respectively. Most alternative fuels generated lower CO and NO_x emissions per unit energy due to their higher volatile matter content, promoting complete combustion. TDF was an exception, exhibiting 2.8 times higher CO emissions. SO₂ emissions were negligible except in the case of TDF (0.14% sulfur content). The measured emission factors were 15–30% lower than theoretical IPCC values, confirming the environmental viability of alternative fuels as coal substitutes in cement production. Full article

This study investigates plastic waste management, focusing on Japan. The volume of plastic waste in Japan is more than eight million tons, and less than a quarter of the plastic waste is subjected to recycling. Considering that Japan is an archipelago consisting of a combination of four large islands and numerous smaller ones, plastic waste that enters the ocean poses significant threats to marine life, birds, other living beings, and beach pollution. This research explores the underlying factors that have made Japan one of the highest users of plastic. In addition, this study evaluates different strategies that are utilized in Japan to deal with the reduction in plastic utilization and plastic waste. The final section of the study proposes strategies that can reduce utilization of plastic and production of plastic waste and the new and future outlook for replacement of plastic. Full article

Thailand generated 27.2 million tons of municipal solid waste in 2024, of which 12% was plastic waste, predominantly single-use plastics. The mismanagement of plastic waste can lead to significant long-term environmental issues, including the release of toxic chemicals through open burning and air pollution, posing risks to human health. Effective and efficient plastic waste collection and recycling are therefore essential to address the reduction and management of plastic waste, as well as to support a low-carbon energy transition. This study assessed three community-driven initiatives by conducting a comparative sustainability assessment of plastic bag recycling under real-life conditions in Thailand using a multi-criteria decision-making framework. The results of the assessment in three municipalities showed that the actual collection rates in all initiatives remained extremely low (0.0014–0.1555%). The highest rankings were observed with recycling initiatives driven by superior collection rates and favorable economic returns. The hindrances to promoting sustainability are found to be due to policy inconsistency, ineffective leadership, and behavioral barriers. The practical collection rates should increase to at least 25% to be more sustainable in terms of economic, social, and environmental aspects compared to those without the recycling initiative. These findings, thus, provide specific targets for improving plastic waste separation and management strategies in all regions facing similar challenges. Full article