Search Results (6)

The expansion of the construction sector in order to meet infrastructure demands is generating millions of tons of solid waste. This waste threatens resource sustainability and increases environmental challenges. Adopting a circular economy (CE) through waste minimization (WM) offers a solution, but policy guidelines are very limited in developing countries, especially in the context of Pakistan. The global body of knowledge lacks a comparative analysis of the influence of the perception of stakeholders when developing such guidelines. Therefore, the purpose of the current study is to identify enablers for the development of a policy framework and to provide a comparative analysis of the perception of stakeholders. In this regard, Saunders’s research onion model and purposive sampling methods were used for the selection of research variables and respondents, respectively. Data were gathered through semi-structured interviews. Thematic analysis, including word frequency and cluster analyses using the NVivo 15 software, was performed. The key findings indicated an 80% agreement and a 60% disagreement among consultant–contractor and contractor–regulator relationships, respectively. Overall, financial support (14.6%) and awareness programs (11.2%) at the macro level, the use of BIM (5%), the clarity of specifications (4.1%), the segregation of onsite waste (2%), and the adoption of reuse and recycling practices (2%) at the micro level were found to be major policy measures. This study concludes with practical implications for sustainable development. Full article

Waste management involves the systematic collection, transportation, processing, and treatment of waste materials generated by human activities. It entails a variety of strategies and technologies to diminish environmental impacts, protect public health, and conserve resources. Consequently, providing an effective and comprehensive optimization approach plays a critical role in minimizing waste generation, maximizing recycling and reuse, and safely disposing of waste. This work develops a novel Possibilistic Multi-Objective Mixed-Integer Linear Programming (PMOMILP) model in order to formulate the problem and design a circular–sustainable–reliable waste management network, under uncertainty. The possibility of recycling and recovery are considered across incineration and disposal processes to address the main circular-economy principles. The objectives are to address sustainable development throughout minimizing the total cost, minimizing the environmental impact, and maximizing the reliability of the Waste Management System (WMS). The Lp-metric technique is then implemented into the model to tackle the multi-objectiveness. Several benchmarks are adapted from the literature in order to validate the efficacy of the proposed methodology, and are treated by CPLEX solver/GAMS software in less than 174.70 s, on average. Moreover, a set of sensitivity analyses is performed to appraise different scenarios and explore utilitarian managerial implications and decision aids. It is demonstrated that the configured WMS network is highly sensitive to the specific time period wherein the WMS does not fail. Full article

Over the years, the building envelope has evolved from a protective barrier element to a complex filter system capable of optimizing the interactions between the external and internal environments. An efficient envelope reacts flexibly to variable external conditions, minimizing heat losses in the winter season. Therefore, insulating materials play a fundamental role in building’s thermal performance. In this scenario, Additive Manufacturing represents an emerging and promising solution for the construction sector. Three-dimensional printing allows the creation of custom geometries, reduces material waste, and automates the construction process. This work aims to compare the thermal performance of a PLA (polylactic acid) 3D-printed block with an internal honeycomb structure whose air cavities are filled with natural and recyclable waste-insulating materials. The selected air cavity filling materials are (i) wood sawdust, (ii) sheep’s wool, and (iii) hemp. The thermal behavior of the block with the different filling materials was experimentally tested via Heat Flow Meter (HFM) method in a controlled environment (Hot Box). The results showed that the introduction of waste material significantly improved the thermal performance of the 3D-printed block compared to the case of air cavities. A thermal transmittance (U-value) reduction of up to 57% was obtained. Moreover, the sheep’s wool showed the best performance, with a U-value equal to 0.53 ± 0.02 W/m²K, i.e., 18.5% less than the wood sawdust and 19.7% less than hemp. Full article

Valorization of agro-food waste through anaerobic digestion (AD) is gaining prominence as alternative method of waste minimization and renewable energy production. The aim of this study was to identify the key parameters for digester performance subjected to kinetic study and semicontinuous operation. Biochemical methane potential (BMP) tests were conducted in two different operating conditions: without mixing (WM) and continuous mixing (CM). Three different substrates, including food waste (FW), chicken dung (CD), and codigestion of FW and CD (FWCD) were used. Further kinetic evaluation was performed to identify mixing’s effect on kinetic parameters and correlation of the kinetic parameters with digester performance (volatile solid removal (VS%) and specific methane production (SMP)). The four models applied were: modified Gompertz, logistic, first-order, and Monod. It was found that the CM mode revealed higher values of Rm and k as compared to the WM mode, and the trend was consistently observed in the modified Gompertz model. Nonetheless, the logistic model demonstrated good correlation of kinetic parameters with VS% and SMP. In the continuous systems, the optimum OLR was recorded at 4, 5, and 7 g VS/L/d for FW, CD, and FWCD respectively. Therefore, it was deduced that codigestion significantly improved digester performance. Electrical energy generation at the laboratory scale was 0.002, 0.003, and 0.006 kWh for the FW, CD, and FWCD substrates, respectively. Thus, projected electrical energy generation at the on-farm scale was 372 kWh, 382 kWh, and 518 kWh per day, respectively. Hence, the output could be used as a precursor for large-scale digester-system optimization. Full article

Advanced technologies call for composting indoors for minimized impact on the surrounding environment. However, enclosing compost piles inside halls may cause the accumulation of toxic pollutants, including carbon monoxide (CO). Thus, there is a need to assess the occupational risk to workers that can be exposed to CO concentrations > 300 ppm at the initial stage of the process. The objectives were to (1) develop a model of CO accumulation in the headspace of the bioreactor during organic waste composting and (2) assess the impact of headspace ventilation of enclosed compost. The maximum allowable CO level inside the bioreactor headspace for potential short-term occupational exposure up to 10 min was 100 ppm. The composting was modeled in the horizontal static reactor over 14 days in seven scenarios, differing in the ratio of headspace-to-waste volumes (H:W) (4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4). Headspace CO concentration exceeded 100 ppm in each variant with the maximum value of 36.1% without ventilation and 3.2% with the daily release of accumulated CO. The airflow necessary to maintain CO < 100 ppmv should be at least 7.15 m³·(h·Mg w.m.)⁻¹. The H:W > 4:1 and the height of compost pile < 1 m were less susceptible to CO accumulation. Full article

The present study constitutes the first social life cycle assessment (SLCA) study in Afghanistan and aims at assessing the social performance of the waste management system (WMS) of Kabul city. The system boundary considered includes households generating the waste, the sanitation department of Kabul city, scavengers, recycling shops, the recycling factory, and the local community living in its vicinity. Compared to previous SLCA studies that consider one stakeholder per organization, we distinguished between the manager and the worker level for each organization. In total, eight stakeholders, 90 inventory indicators, and 20 impact subcategories were investigated. Results show three main social issues: the overwork of scavengers, recycling shop owners and recycling factories’ workers and managers, the absence of communication and implication of the local community, and the poor cleanliness of the surroundings of the recycling factory and collection points. At the sanitation department, managers were found facing more psychological stress and overwork than workers, demonstrating the current isolation of the department inside Kabul’s local government. It seems nonetheless possible to improve Kabul’s WMS by redesigning the location of garbage bins and conducting communication campaigns towards consumers and the local community. That would help to minimize the nuisances associated with the handling of waste and to integrate better waste management activities into the socio-economy of Kabul city. Full article