Urbanization and solid waste production: prospects and challenges

The 15-minute city concept: The case study within a neighbourhood of Thessaloniki

Cities, crucial cultural hubs, mould individual and group identities. The global urban expansion, with over half the population in urban areas, presents interconnected challenges such as pollution, poverty, inequality, ageing infrastructure, resource overconsumption, land use changes, biodiversity impact and climate change. Addressing these demands ambitious actions targeting political, social and economic systems for transformative change. The theoretical framework guiding city transformation centres on an interdisciplinary approach influenced by the Smart and Green Transition. The '15-minute city' concept, emphasizing human scale and urban experience, proposes that cities enable residents to meet daily needs within a short walk or bike ride. The aim of this study was the exploration of its implementation in Greek cities, particularly Thessaloniki, which reveals inherent characteristics supporting the 15-minute concept. Through an interdisciplinary approach rooted in the Smart and Green Transition framework, the research provides concrete guidance for policymakers in tailoring urban planning strategies, allocating resources effectively and crafting policies conducive to successful and sustainable urban transformations. Moreover, prioritizing public engagement highlights the significance of community involvement in shaping urban development plans, ensuring that proposed initiatives align with residents' needs and desires. In essence, this research contributes tangible insights and actionable recommendations for Greek cities, paving the way for more liveable, resilient and sustainable urban environments.

The P-graph approach in optimal synthesis and planning of waste management towards achieving sustainable development goals: A systematic review

Effective waste management remains a challenge in global environmental sustainability, underlining the urgent necessity for innovative solutions. This review explored waste management strategies, focusing on the role of P-graph frameworks in achieving sustainable development goals (SDGs). P-graphs offer a systematic approach across domains including, chemical reaction routes, carbon management networks, economic systems and resource planning to waste management synthesis and planning. Through a systematic search and analysis of relevant P-graph approaches, 28 articles meeting the inclusion criteria were selected for review. The study reveals that P-graph approach is a systematic methodology that can streamline decision-making processes, which ultimately lead to more efficient and effective waste management strategies and solutions. This research also highlighted the absence of previous studies on the application of the P-graph approach to various types of waste, underscoring its significance and originality in the field. This study seeks to advance the achievement of SDGs and promote sustainable waste management practices through the integration of the P-graph framework with waste management solutions.

Bio-based resources: systemic & circular solutions for (agro)environmental services

The global promotion of decarbonisation through the circular solutions and (re)use of bio-based resources (BBR), i.e. waste streams, notably from the agricultural, forest and municipal sectors has steadily increased in recent decades. Among the transformative solutions offered by BBR, biosolids (BS), biochars (BC), and bioashes (BA) specifically attract scientific attention due to their highly complex organo-mineral matrices, which present significant potential for recovery in the agro-/forest-ecosystems. These materials enhance various soil (i) chemical (pH, macro/micro nutrient concentrations, organic matter content), (ii) physical (porosity, water-air relations, compaction) or (iii) microbial (diversity, activity) properties. Furthermore, some of transformed BBR contribute to a multitude of environmental services such as the remediation of contaminated sites and wastewater treatment, employing cost-effective and eco-friendly approaches that align with circular economy/waste management principles, ultimately contributing to climate change mitigation. However, several challenges impede the widespread utilization/transformation of BBR, including technological limitations in processing and application, concerns about contamination (e.g., PAHs, PCBs, micro/nano plastics present in BS), toxicity issues (e.g., heavy metals in BA or nanoparticles in BC), and regulatory constraints (e.g., non-uniform regulations governing the reuse of BA and BS). Addressing these challenges demands an interdisciplinary and intersectoral approach to fully unlock the potential of BBR in sustainable decarbonisation efforts.

Mycelium-Based Composites as a Sustainable Solution for Waste Management and Circular Economy

The global population is expected to increase by nearly 2 billion individuals over the next three decades, leading to a significant surge in waste generation and environmental challenges. To mitigate these challenges, there is a need to develop sustainable solutions that can effectively manage waste generation and promote a circular economy. Mycelium-based composites (MBCs) are being developed for various applications, including packaging, architectural designs, sound absorption, and insulation. MBCs are made by combining fungal mycelium with organic substrates, using the mycelium as a natural adhesive. Mycelium, the vegetative part of fungi, can be grown on various organic feedstocks and functionalized into a range of diverse material types that are biobased and thus more sustainable in their production, use, and recycling. This work aims to obtain mycelium-based composites with acoustic absorption properties, using coffee grounds and agricultural waste as raw materials. The topic approached presents a new method of recovering spent coffee grounds that does not involve high production costs and reduces two current environmental problems: noise pollution and abundant waste. Measurements of the normal-incidence sound absorption coefficient were presented and analyzed. Mycelium-based composites offer an innovative, sustainable approach to developing bio-composite sound-absorbing surfaces for interior fittings. The material by Ganoderma lucidum exhibits exceptional sound-absorbing properties at frequencies below 700 Hz, which is a crucial aspect of creating sound-absorbing materials that effectively absorb low-frequency sound waves. The modular construction system allows for a high degree of flexibility to adapt to short-term changes in the workplace.

Investigating municipal waste Kuznets curve for 22 OECD countries

Treating waste as a resource can provide many social and economic benefits and develop policies accordingly. In this study, the relationship between municipal waste, income, human capital, material footprint, consumption and urban population is analyzed with panel data models within the framework of the Kuznets curve, using the data for the period of 1995 - 2018 for 22 OECD countries. Various economic, demographic and human variables that are thought to have an impact on municipal waste generation were added to the models created with cubic functional forms. The analysis results show that the relationship between municipal waste and income is inverted N-shaped. In line with expectations, the increase in human capital reduces the amount of waste per capita. The urbanization rate causes a higher increase in the amount of waste per capita compared to the population. Real consumption per capita and material footprint similarly have a positive effect on waste. The findings have calculated the first and second-order conditions for an inverted N-shaped relationship and verified that this relationship is mathematically valid.