Development and application of a comprehensive methodology for the analysis of global and local emissions of energy systems

The energy sector is a source of economic and social progress, but it is also the main responsible of air pollution resulting from human activity, mainly from the combustion of fossil fuels and bioenergy. The impacts on atmosphere may be divided into global effects, due to change in concentration of greenhouse gases, and regional/local effects, due to the dispersion of SO2, NOx, particulates and other gases. The aim of this thesis is the development and application of a methodology for calculating the emissions in atmosphere associated with energy management interventions. The methodology aims to characterize and quantify the environmental impacts affecting both the local and global scale. The pollutants involving local effects considered in this study are nitrogen oxides and particulate matter. Globally, the emission of greenhouse gases is considered, by quantifying the equivalent CO2 (CO2eq) emitted. The environmental impact of an energy option is quantified in terms of its emission balance, i.e. by comparing the present situation with one (or more) future scenarios. The study at the local scale also considers the dispersion of pollutants using modelling tools. The methodology is applied to two case studies located in the Italian Metropolitan City of Turin, characterized by different application contexts and different scales of operation. The first case study is represented by a system for the production and conversion of biogas and biomethane. The analysis of global emissions considers four different operating scenarios. The results show a CO2 reduction of 1426 t/y for biogas combustion in full cogeneration mode (generation of both heat and electricity). Biomethane for transports scenario provides a similar result (1379 t/y). If biogas combustion with partial cogeneration is considered (generation of electricity only), the CO2 balance approaches to zero. The evaluation of local impacts is made with two different dispersion models. The application of an Octave-based Gaussian model provides an average increase of concentration both for NOx and TSP, in the order of units of g/m3. The results of CALPUFF model simulations show a slight decrease of concentration in the order of 10-2 g/m3. The second case study consists of a potential extension of the district heating network in the urban area of Turin. The production of local emissions is calculated considering the operation of the main power plants in response to the estimated heat demand. Avoided emissions are calculated simulating the heat production of centralized residential heaters. The results of CALPUFF model simulations show a potential reduction of NOx average concentration between 1 and 6 g/m3. The results of global emissions show an unfavorable balance in the order of 104 t/y of CO2, that varies depending on the assumptions on the emission factors of the power units. A comprehensive final discussion is reported after the analysis of the two case studies. The calculation of two indicators (the “thermal benefit vs. local emission indicator” and the “local to global emission ratio”) is also included to discuss a possible standardization of the proposed methodology. This study provides important information on the effects on air quality resulting from the modification of the energetic management of an area or settlement. The employed methodology is consistent and comprehensive in identifying the potential optimal solutions for energy production and management, as well as identifying the consequences to a given scenario under an environmental point of view

DISTRICT HEATING SYSTEM: EVALUATION OF ENVIRONMENTAL AND ECONOMIC ASPECTS

With the need of limiting pollutants emissions, careful management of energy plants should be considered to reduce the footprint that can be caused by these systems. Advantages of district heating (DH) systems have been linked to a decrease in local and global emissions, centralized heat production located outside urban centres, possible utilization of renewable heat sources. District heating, consisting of the distribution of hot water by means of underground networks for the buildings’ heating and sanitary water, is an ever-expanding technology that allows the optimization of energy resources, with positive consequences in terms of both economic savings and environmental impacts. The aim of this work is to analyse the district heating system from an environmental point of view, in way to realize a general procedure of evaluation. To this end, the Italian city of Turin is taken as case study. Turin has long been subject to high concentration levels of pollutants, especially NOx and particulate. The environmental compatibility of extending the district heating network is evaluated. Two different tools are used: first, the environmental balance is defined to perform an evaluation of the flux modification at the emission sources; secondly, the atmospheric impacts of emissions are estimated using CALPUFF dispersion model. The results show a future reduction in overall NOx emission, as well as a reduction of ground level average NOx concentration ranging between 0.2 and 4 μg/m3. This study provides important information on the effects of a change of the energy configuration on air quality in an urban area. The proposed comprehensive methodology is applicable for other similar cases

An Overview of Thermal Treatment Emissions with a Particular Focus on CO2 Parameter

Waste-to-energy (WtE) technologies can offer sustainable solutions for waste that cannot be further reused or recycled, such as the part of municipal solid waste (MSW) that is not suitable for recycling processes. The two main (most widely used) thermal treatment technologies that can be applied to MSW are direct combustion in an incineration plant and gasification. This paper examines in particular the direct combustion in incineration plants, explaining the main process, the main technologies applied, and the resulting environmental aspects. Moreover, this work focuses on analyzing flue gas emissions from thermal treatment in order to better understand the impacts of these kinds of processes. A particular focus on the CO2 parameter is performed. CO2 is a persistent atmospheric gas, and it is one of the greenhouse gases (GHGs) potentially responsible for the climate change phenomenon. In this sense, specific indexes (tCO2/tMSW and tCO2/MWh) are elaborated considering the thermal treatment plants present in six Italian regions. The main aim of this review paper is to try to fill the gap that still exists regarding the emissions environmental compatibility coming from these type of plants, the evaluation of the amount of CO2 emitted, and the possible reduction of the CO2 parameter. One of the main outcome obtained is in fact the evaluation of the amount of CO2 coming from these kinds of plants and some indications about the technological possibilities of reducing this amount

Conceptualizing environmental effects of carsharing services: A system thinking approach

Emerging carsharing services and their interconnections with other modes of urban transport, regulations, car manufacturing and population have affected the dynamics of energy consumption, environmental pollution and greenhouse gas emission within a complex system. However, although some aspects of environmental impacts of transport sector have been investigated in the literature, well-deserved studies on the environmental effects of carsharing services following a system thinking approach is missing. This research aims at providing a comprehensive conceptual framework to systematize the interconnections between carsharing services and their environmental effects. To do this, system dynamics (SD) modeling, as a tool to simulate complex and dynamic systems, is applied and the proposed framework model is illustrated by using a causal-loop diagram (CLD). Along with analyzing the main identified causal loops within the presented CLD, relevant strategies are proposed to reduce the negative environmental effects associated with the carsharing services, considering the whole lifecycle of a shared vehicle. The proposed framework can help environment policy makers and shared mobility practitioners in long-term strategic decision-making. Moreover, it can be applied by the researchers as a basis for future research, not only for SD modeling but also other simulation and analysis structures

Air quality and photochemical reactions: analysis of NOx and NO2 concentrations in the urban area of Turin, Italy

In this work, based on the existing studies on photochemical reactions in the lower atmosphere, an analysis of the historical series of NOx, NO2, and O3 concentrations measured in the period 2015–2019 by two monitoring stations located in the urban area of Turin, Italy, was elaborated. The objective was to investigate the concentration trends of the contaminants and evaluate possible simplifed relationships based on the observed values. Concentration trends of these pollutants were compared in diferent time bands (diurnal or seasonal cycles), highlighting some diferences in the dispersion of the validated data. Calculated [NO2]/[NOx] ratios were in agreement with the values observed in other urban areas worldwide. The infuence of temperature on the [NO2]/[NOx] ratio was investigated. An increase of [NO2]/[NOx] concentration ratio was found with increasing temperature. Finally, a set of empirical relationships for the preliminary determination of NO2 concentration values as a function of the NOx was elaborated and compared with existing formulations. Polynomial functions were adapted to the average concentration values returned by the division into classes of 10 μg/m3 of NOx. The choice of an empirical function to estimate the trend of NO2 concentrations is potentially useful for the preliminary data analysis, especially in case of data scarcity. The scatter plots showed diferences between the two monitoring stations, which may be attributable to a diferent urban context in which the stations are located. The dissonance between a purely residential context (Rubino station) and another characterised by the co-presence of residential buildings and industries of various kinds (Lingotto station) leads to the need to consider a greater contribution to the calculation of the concentrations emitted in an industrial/residential context due to a greater presence of industrial chimneys but also to more intense motorised vehicle transport. The analysis of the ratio between nitrogen oxides and tropospheric ozone confrmed that, as O3 concentration increases, there is a consequent reduction of NOx concentration, due to the chemical reactions of the photo-stationary cycle that takes place between the two species. This work highlighted that the use of an empirical formulation for the estimation of [NOx] to [NO2] conversion rate could in principle be adopted. However, the application of empirical models for the preliminary estimation of [NOx] conversion to [NO2] cannot replace advanced models and should be, in principle, restricted to a limited area and a limited range of NOx concentration

Implementing Air Pollution and Health Damage Costs in Urban Multi-Energy Systems Modelling

The growing global urbanization rate implies that the sustainability challenges are increasingly concentrated in cities. At today, around 75% of global energy is consumed in urban areas, so efforts must be addressed to transform existing urban energy systems into more sustainable systems. In this perspective, a key aspect to evolve toward a cleaner and affordable energy system is the development of Multi-Energy Systems (MES) modelling, whereby heat, electricity, fuels, transport, and other energy carriers closely interact with each other at various scales. MES can optimize technical, economic and environmental performance with respect to “traditional” independent energy systems, at both the operational and the planning stage. This paper presents a development of the existing MESsi modelling platform, consisting in the implementation of a model estimating the impacts on air quality and human health. MESsi is a novel distributed infrastructure for modelling and co-simulating Multi-Energy-Systems. It exploits modern software design patterns (i.e. microservices) to guarantee scalability, extendibility and easy maintenance of the system. Thus, MESsi is flexible in modelling and co-simulating different energy flows in a single solution made of different interoperable modules that can be deployed in a plug-and-play fashion. The module to be implemented in MESsi infrastructure is the DIATI integrated dispersion and externalities model (DIDEM). The DIDEM model is based on the impact pathway approach, linking the simulation of pollutants dispersion to the concentration-exposure-response functions provided by latest WHO recommendations. An overview of the potential integration steps in the modelling infrastructure is described in this paper. A discussion on possible application scenarios that have different spatio-temporal resolutions is also reported. The integration of DIDEM model in MESsi platform allows the inter-connection of a detailed impact assessment to a high-level energy system simulation

Hard-to-recycle plastics in the automotive sector: Economic, environmental and technical analyses of possible actions

The use of plastics in the automotive industry is favoured by their relatively low cost, but a sustainable treatment at their end of life is still challenging. The objective of this study is to contribute to the identification of best practices to increase the recovery rate of plastic materials from end-of-life vehicles (ELVs). European regulations for ELVs foresee that the reuse/recovery and reuse/recycling had to be increased to a minimum of 95% and 85% of the vehicle weight respectively by 2015. Three areas with room for possible improvement were identified in this study: the dismantling phase, the recycling processes, and the material recovery from automotive shredder residues (ASRs) as solid recovered fuels (SRFs). The economic feasibility of recovering specific plastic compo- nents from ELVs was assessed using a criterion based on the cost of dismantling, recycling and disposal of the components, as well as the environmental costs of the processes. Based on the results, disassembly and recycling could be cost-effective for a disassembly time below 180 s and a component mass above 600 g. For the recycling processes, the Life Cycle Assessment (LCA) methodology was applied to evaluate the environmental impacts of recycling HDPE from fuel tanks, polyamides PA6/PA66 and PET from automotive components. As the climate change indicator is concerned, Tthe LCA study showed that the impact for 1 kg of these secondary raw materials is respectively of 0.83, 0.16/0.17 and 2.17 kg CO2 eq, obtained from these fractions resulting more sustainable than the respective virgin materials. Electricity consumption was among the main contributors to the potential environmental impacts. The characterization process of ASRs was conducted to assess their compliance to certain types of SRFs. According to the results of the industrial tests, the treatment facility can recover only around 74% of an ELV. The characteristics of ASRs were compliant to be assimilated to a SRF. This study showed that the amount of plastics recoverable from ELVs has the potential to increase thus facilitating the fulfilment of EU recovery targets