Environmental Impacts of Electricity from Incineration and Gasification: How the LCA Approach Can Affect the Results

Waste-to-energy (WtE) technologies can offer sustainable solutions for waste, which can no more be reused or recycled, such as the part of municipal solid waste (MSW) that is not suitable for recycling processes. This study focused on the environmental consequences of the production of electricity from incineration and gasification of MSW. To this aim, the standardised life cycle assessment (LCA) methodology was used. A life cycle inventory, mainly composed by primary data, is provided. Starting from these data, different highly shared LCA approaches were used to calculate the potential impacts of 1 kWh provided by the two analysed WtE technologies. The different approaches concern the method of accounting for the by-products (through an economic allocation and a system expansion) and the inclusion/exclusion of environmental benefits due to the avoided landfill for the MSW. For each approach, impact-assessment results were calculated with the ReCiPe midpoint (H) method. A comparison was carried out (i) between the results obtained for the same WtE technology but calculated with different approaches and (ii) between the impact results of electricity generated by the two WtE technologies calculated with the same approach. From the study, it emerged that, according to the accounting rules, the impact results can significantly change and, for some impact categories, even lead to opposite conclusions. In the absence of category rules that harmonise the environmental assessments of WtE processes, it is therefore recommended that the development/use/reproduction/comparison of studies focused on the valorisation of waste should be carried out with caution

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

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

End-of-Life Tyres: Comparative Life Cycle Assessment of Treatment Scenarios

Waste tyres and their accumulation is a global environmental concern; they are not biodegradable, and, globally, an estimated 1.5 billion are generated annually. Every year around 350,000 tons of end-of-life tyres (ELT) are managed in Italy, collected from cars, two-wheeled vehicles, trucks, up to large quarry vehicles and agricultural vehicles. ELTs are collected and sent for material or energy recovery, in line with the circular economy principles. This paper investigates the environmental impacts of two common scenarios of ELT treatments. Specifically, it is analysed the recycling of crumb rubber (CR, deriving from the tyre shredding) for the composition of bituminous mixtures for the wearing course of roads. This scenario is compared with the energy recovery route in a dedicated incinerator. To this aim the standardised methodology of Life Cycle Assessment (ISO 14040-44) is employed. Results shows that for most part of the impact categories analysed, the material recovery presents higher environmental benefits if compared with energy recovery

Enhancing the Energy Efficiency of Wastewater Treatment Plants through the Optimization of the Aeration Systems

The current geopolitical landscape of the European Union has made it clear that the energy sector must be a top priority in EU policy, especially in light of the sudden escalation of Russian– Ukrainian conflicts. Energy efficiency has been used as the first tool of EU policy to tackle energy and climate crises, given the issues surrounding energy vulnerability and the need to limit gas emissions that contribute to climate change. The white certificate mechanism in Italy has played a pivotal role in encouraging measures to achieve the country’s energy-saving goals. Given the high energy requirements of Wastewater Treatment Plants (WWTPs), especially for aeration in the biological section, this paper examines the replacement of the air distribution system for a large WWTP as a viable intervention. In order to provide economic perspective for the plant, both the discounted Payback Period (dPBP) and the Net Present Value (NPV) were calculated for the investment. When viewed through an economic lens, the dPBP metric exhibits values that span from less than 1 year to nearly 4.5 years. Additionally, the investment’s cost-effectiveness was emphasized by the NPV, which, depending on the factors considered, can exceed 17.5 million euros. Finally, given the centrality of the theme of climate change, the avoided greenhouse gas emissions generated by the efficiency intervention were calculated, according to the GHG Protocol, resulting in a quantity of avoided emissions equivalent to over 57,770 tonnes of CO2e. These results highlight important achievements in terms of both the cost-effectiveness of the plant and the reduction of greenhouse gas emission

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

Nature Based Solution As Flood Protection Strategies: The Case Of Caraha River Park, Brazil

Following the road paradigm, many cities, at the beginning of the 20th century, experienced a reckless increase in the number of vehicles on the road causing an unsustainable urban and environmental situation. The origin of the problem surely lies in the occupation of the preserved areas. In many South American states, for example, highways generally ignore the presence of environmental obstacles (such as rivers) as they may cause a “delay in modernization”. As a result, riparian forests are invaded and turned into highways, water beds are channeled and most rivers are contaminated with wastewater. Due to the occupation of green and riparian areas, urban floods have become more and more and consequently urban spaces have been disqualified. This situation also involved the Carahá River that crosses the city of Lages in southern Brazil, in fact the river embankment has become completely impermeable due to the construction of an urban road. Proposing urban spaces with an emphasis on improving environmental quality and integrating forms of public transport are basic points that could lead to the sustainable development of our cities. In this context, the aim of this research is to propose a sustainable river project for the Carahá River, with the aim of presenting nature-based solutions to prevent floods and improve the environmental, functional and aesthetic quality of the city. To develop this research, first theoretical studies were carried out on the relationship between rivers and cities, secondly three international case studies and related literature were analyzed with the aim of deepening the knowledge of the connection between rivers and population. Finally, an intensive study of the territory was carried out and a social analysis was conducted through a semi-structured interview in which the population of Lages participated. The result of this study contributed to effectively defining the intervention guidelines for the Carahá river park project considering, as an added value, also the main needs of citizens

Environmental Impacts in the Textile Sector: A Life Cycle Assessment Case Study of a Woolen Undershirt

The textile industry, known for its significant contribution to global greenhouse gas emissions, is increasingly active in exploring techniques and technologies to improve its environmental performance. The main tool to calculate environmental impacts is the Life Cycle Assessment (LCA) methodology, which is standardized and internationally recognized. Specific guidelines for the impact calculation of textile products are under development (Product Environmental Footprint Category Rules (PEFCRs) for the category of Apparel and Footwear). In this context, this study contributes to the knowledge in the textile sector through the development of a cradle-to-gate LCA of a woolen undershirt produced in Italy. This study shares robust and recent (2021) primary data for the phases of weaving, cutting, and sewing, obtained from an Italian company. Data from previous studies of the authors, as well as secondary data, are also used to complete the inventory. A further analysis is developed to include the use phase as well. The impact on climate change of one undershirt results in 11.7 kg CO2 eq, primarily due to the farming phase of sheep, which accounts for 88% of the total emissions. The impact on climate change of energy used in the wool transformation process has a relatively low impact (11%), also thanks to the partial use of electricity produced by photovoltaic panels, while materials (e.g., chemicals) and transportation have negligible contributions. The farming phase, despite relying on secondary data, is identified as the primary contributor for most of the other indicators. Additionally, it has been found that user habits play a key role in the impact related to one wearing of the undershirt. The findings suggest that further work is necessary in the textile sector and emphasize (i) the need for guidelines, enabling the inclusion of the use phase without compromising the comparability between different LCAs of similar textile products; (ii) the need for improved traceability practices in the textile sector, to enhance inventory data collection on the raw material production (wool fibers in the case under analysis)