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The increasing demand for energy and commodities has led to escalating greenhouse gas emissions, the chief of which is represented by carbon dioxide (CO2). Blue hydrogen (H2), a low-carbon hydrogen produced from natural gas with carbon capture technologies applied, has been suggested as a possible alternative to fossil fuels in processes with hard-to-abate emission sources, including refining, chemical, petrochemical and transport sectors. Due to the recent international directives aimed to combat climate change, even existing hydrogen plants should be retrofitted with carbon capture units. To optimize the process economics of such retrofit, it has been proposed to remove CO2 from the pressure swing adsorption (PSA) tail gas to exploit the relatively high CO2 concentration. This study aimed to design and numerically investigate a vacuum pressure swing adsorption (VPSA) process capable of capturing CO2 from the PSA tail gas of an industrial steam methane reforming (SMR)-based hydrogen plant using NaX zeolite adsorbent. The effect of operating conditions, such as purge-to-feed ratio and desorption pressure, were evaluated in relation to CO2 purity, CO2 recovery, bed productivity and specific energy consumption. We found that conventional cycle configurations, namely a 2-bed, 4-step Skarstrom cycle and a 2-bed, 6-step modified Skarstrom cycle with pressure equalization, were able to concentrate CO2 to a purity greater than 95% with a CO2 recovery of around 77% and 90%, respectively. Therefore, the latter configuration could serve as an efficient process to decarbonize existing hydrogen plants and produce blue H2.

Abstract The sustainable indicators are characterized by a low degree of aggregation and a high amount of information. An indicator must show a synthetic representation of a real environmental, by using a value or a parameter, so that they can be easily used by policy makers. It is necessary to connect, therefore, the various systems in an appropriately integrated sustainable system. The indicators need to be aggregated based on the structure of the data. Each indicator must to be defined through a weight with reference to another weighted indicator. In this paper is illustrated the calculation of the assigned weights that uses a procedure based on fuzzy logic and to define a model that allows us to estimate the sustainability of a city. The final result is, therefore, a combination of values assigned by expert opinion for the various criteria, processed using fuzzy logic to obtain a weight with significant objectivity and as it is possible to estimate the sustainability of the city through the weights.

Abstract In recent years, distributed energy systems (DESs) have been recognized as a promising option for sustainable development of future energy systems, and their application has increased rapidly with supportive policies and financial incentives. With growing concerns on global warming and depletion of fossil fuels, design optimization of DESs through economic assessments for short-run benefits only is not sufficient, while application of exergy principles can improve the efficiency in energy resource use for long-run sustainability of energy supply. The innovation of this paper is to investigate exergy in DES design to attain rational use of energy resources including renewables by considering energy qualities of supply and demand. By using low-temperature sources for low-quality thermal demand, the waste of high-quality energy can be reduced, and the overall exergy efficiency can be increased. The goal of the design optimization problem is to determine types, numbers and sizes of energy devices in DESs to reduce the total annual cost and increase the overall exergy efficiency. Based on a pre-established DES superstructure with multiple energy devices such as combined heat and power and PV, a multi-objective linear problem is formulated. In modeling of energy devices, the novelty is that the entire available size ranges and the variation of their efficiencies, capital and operation and maintenance costs with sizes are considered. The operation of energy devices is modeled based on previous work on DES operation optimization. By minimizing a weighted sum of the total annual cost and primary exergy input, the problem is solved by branch-and-cut. Numerical results show that the Pareto frontier provides good balancing solutions for planners based on economic and sustainability priorities. The total annual cost and primary exergy input of DESs with optimized configurations are reduced by 21–36% as compared with conventional energy supply systems, where grid power is used for the electricity demand, and gas-fired boilers and electric chillers fed by grid power for thermal demand. A sensitivity analysis is also carried out to analyze the influence of energy prices and energy demand variation on the optimized DES configurations.

Abstract The European Energy Efficiency Building Directive 2002/91/CE, as well as other acts and funding programs, strongly promotes the adoption of passive strategies for buildings, in order to achieve indoor thermal comfort conditions above all in summer, so reducing or avoiding the use of air conditioning systems. In this paper, the energy performances achievable using an earth-to-air heat exchanger for an air-conditioned building have been evaluated for both winter and summer. By means of dynamic building energy performance simulation codes, the energy requirements of the systems have been analysed for different Italian climates, as a function of the main boundary conditions (such as the typology of soil, tube material, tube length and depth, velocity of the air crossing the tube, ventilation airflow rates, control modes). The earth-to-air heat exchanger has shown the highest efficiency for cold climates both in winter and summer. The possible coupling of this technology with other passive strategies has been also examined. Then, a technical-economic analysis has been carried out: this technology is economically acceptable (simple payback of 5–9 years) only in the cases of easy and cheap moving earth works; moreover, metallic tubes are not suitable. Finally, considering in summer a not fully air-conditioned building, only provided with diurnal ventilation coupled to an earth-to-air heat exchanger plus night-time ventilation, the possible indoor thermal comfort conditions have been evaluated.

The uncontrolled growth of urban areas worldwide is pushing a substantial part of the urban population to the fringes of society, confining them to the unsecure and unhygienic settlements that we call “informal.” These settlements lack in intelligible layout and essential services and infrastructures, thus representing a challenging issue for policy makers and urban designers in the development of renewal programs and strategies. In order to support the facing of these issues through an on-site upgrade approach, this paper argues that walkability deeply affects the functioning of informal settlements, so as to propose that they can be identified as “proximal cities,” which expresses the idea that the vital space in informal settlements has soft boundaries and follows a fuzzy logic. A quantitative analysis, based on a configurational approach, and a qualitative analysis, focused on the morphologic features of the settlements, have been implemented. A comparison of the results shows that this approach is suitable to provide a deeper knowledge on informal settlement and informal society under the assumption of their strict mutual connection. A primal definition of proximal cities, suitable for describing some properties of autopoietic urban systems, emerges from the evidence-based relationships between their spatial and social features. In this respect, a case study has been proposed and discussed.

Abstract A new analytical methodology aimed at characterizing the energy performance of new and existing buildings is proposed for both winter and summer and with reference to entire urban context, and the methodology is transferred into Geographic Information Systems (GISs). The main target is the evaluation of criticalities of the building stock, promoting effective design for new buildings and proper refurbishment of existing buildings. In this regard, the application of standardized procedures is too onerous if the goal is the qualitative distribution of the energy performances with reference to entire urban areas. The energy demands for space heating are evaluated by simplifying the methodology of the European Standard EN ISO 13790, while with reference to summer cooling, a new hybrid method has been specifically developed. The whole method was applied to the entire historical center of the Italian city of Benevento and, thus, to more than 500 buildings. Moreover, comparisons with measured/evaluated energy requests have been performed to identify the reliability of the methodology. Information on energy performances in the whole city center, moreover, allowed for the setting of “Urban Energy Maps,” a tool dedicated to local government, usable for advanced energy planning and territorial control in energy supply.

PurposeThe pressure of globalization has raised social concerns related to the protection of the environment, forced companies to use sustainability as a strategic weapon to fulfill the legal obligations and achieve overall competitiveness. It is reported that small- and medium-sized enterprises (SMEs) are globally responsible for approximately 70 percent of the industrial pollution, justifying urgent attention to the operations of these businesses. The purpose of this paper is to analyze the impact of sustainability orientation (SO) and supply chain (SC) integration implemented by SMEs on their sustainable procurement (SP) and design. Moreover, this study examines how SMEs’ SP and design affect their environmental and cost performance (CP).Design/methodology/approachThe authors develop a comprehensive model to test the relationships among SC, SC integration, SP, sustainable design (SD), environmental performance (EP) and CP at the SMEs level. The authors investigate the relationships of the mentoned factors by a data set that is collected from 358 Indian manufacturing SMEs.FindingsThe results indicate that in the SMEs’ context: SO positively influences both SP and SD; external integration positively affects SP; internal integration positively affects SD; SP positively influences EP and has not impact on CP; and SD positively influences both EP and CP.Originality/valueThis study provides a broad view of the relation between driving factors that may direct SMEs toward a better sustainability performance and offers practical managerial insights into these important business entities.

The study aims to investigate the factors that are associated with fatal and severe vehicle–pedestrian crashes in Great Britain by developing four parametric models and five non-parametric tools to predict the crash severity. Even though the models have already been applied to model the pedestrian injury severity, a comparative analysis to assess the predictive power of such modeling techniques is limited. Hence, this study contributes to the road safety literature by comparing the models by their capabilities of identifying the significant explanatory variables, and by their performances in terms of the F-measure, the G-mean, and the area under curve. The analyses were carried out using data that refer to the vehicle–pedestrian crashes that occurred in the period of 2016–2018. The parametric models confirm their advantages in offering easy-to-interpret outputs and understandable relations between the dependent and independent variables, whereas the non-parametric tools exhibited higher classification accuracies, identified more explanatory variables, and provided insights into the interdependencies among the factors. The study results suggest that the combined use of parametric and non-parametric methods may effectively overcome the limits of each group of methods, with satisfactory prediction accuracies and the interpretation of the factors contributing to fatal and serious crashes. In the conclusion, several engineering, social, and management pedestrian safety countermeasures are recommended.

The configuration of a biologically fertile substrate for edible plant growth during long-term manned missions to Mars constitutes one of the main challenges in space research. Mars regolith amendment with compost derived from crew and crop waste in bioregenerative life support systems (BLSS) may generate a substrate able to extend crew autonomy and long-term survival in space. In this context, the aim of our work was threefold: first, to study the geochemistry and mineralogy of Mojave Mars Simulant (MMS-1) and the physico-chemical and hydraulic properties of mixtures obtained by mixing MMS-1 and green compost at varying rates (0:100, 30:70, 70:30, 100:0; v:v); secondly, to evaluate the potential use of MMS-1 as a growing medium of two lettuce (Lactuca sativa L.) cultivars; thirdly, to assess how compost addition may impact on sustainability of space agriculture by exploiting in situ resources. MMS-1 is a coarse-textured alkaline substrate consisting mostly of plagioclase, amorphous material and secondarily of zeolite, hematite and smectites. Although it can be a source of nutrients, it lacks organic matter, nitrogen, phosphorus and sulphur, which may be supplied by compost. Both cultivars grew well on all mixtures for 19 days under fertigation. Red Salanova lettuce produced a statistically higher dry biomass, leaf number and area than Green Salanova. Leaf area and plant dry biomass were the highest on 30:70 simulant:compost mixture. Nevertheless, the 70:30 mixture was the best substrate in terms of pore-size distribution for water-plant relationship and the best compromise for plant growth and sustainable use of compost, a limited resource in BLSS. Many remaining issues warrant further investigation concerning the dynamics of compost production, standardisation of supply during space missions and representativeness of simulants to real Mars regolith.

Due to the decreasing availability of virgin materials coupled with an increased awareness of environmental sustainability issues, many researchers have focused their efforts on investigating innovative technological solutions in the civil engineering domain. This paper aims to evaluate the suitability of construction and demolition waste (C and DW) and reclaimed asphalt pavement (RAP) reused within asphalt mixtures (AMs) prepared for the binder layer of road pavements. Both hot and cold mixing methodologies were investigated. The technical assessment was based on the volumetric and mechanical suitability, according to saturated surface dry voids (SSDV) and indirect tensile strength (ITS) tests carried out at 10 °C, respectively. Laboratory findings showed that all the hot AMs matched the desired target SSDV at the design gyrations number at different optimum bitumen content levels, alternatively showing a non-significant variation or a significant increase in ITS compared to conventional hot mix asphalt. Conversely, the cold AMs with cement and emulsion bitumen showed a greater volume of voids and moisture sensitivity, and lower temperature susceptibility compared to hot AMs, reaching, on average, 11% lower ITS when using coarse C and DW aggregates and 43% lower ITS when using filler from C and DW. These volumetric and mechanical properties were modeled by means of support vector machines and categorical boosting (CatBoost) machine learning algorithms. The results proved to be satisfactory, with CatBoost determination coefficients R2 referring to SSDV and ITS equal to 0.8678 and 0.9916, respectively. This allowed for the mechanical performance of these sustainable mixtures to be predicted with high accuracy and implemented within conventional mix design procedures.