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Cities are a major source of greenhouse gas emissions (GHGs), but they can play a significant role in climate change mitigation by adopting and implementing GHG emission reduction plans, policies and measures. Circular economy measures are recognized to contribute significantly to decarbonization. However, in the literature there is a lack of quantitative analyses on circular measures in cities and their impact on urban GHG emissions. The paper aims to contribute to the literature on the relation between circular cities and climate change mitigation by focusing on circular interventions applicable in three high-impact sectors in cities: energy systems, mobility and built environment, in order to investigate their impacts in terms of emission reductions and contribution to decarbonization. The study covers four cities around the world accounting for more than 10 million of inhabitants and 2,000 km2 of metropolitan area: Bogotá, Colombia; Genoa and Milan, Italy; Glasgow, UK. The methodology uses a Global Trade Analysis Project (GTAP) modelling approach to develop production and consumption-based emission baselines for the four cities and to assess impacts of selected circular measures in the three sectors on the baselines. According to the in-depth analysis of the four considered urban contexts, the majority of the emissions generated by activities carried out within the urban borders are emitted outside the borders in the form of emissions scope 3, thus demonstrating how today's cities are large consumers of goods produced outside their borders, requiring the use of a consumption-based approach for emissions inventory. The results on the modelling of the GHG reduction impact of circular measures show that there is a relevant emission reduction potential in Scope 1 and 2 emissions in cities and highlight the need to prioritize decarbonization of electricity supply in order to ensure relevant emission reductions across the three sectors. The results also demonstrate the potential to reduce supply-chain Scope 3 emissions through urban measures. [Display omitted] • Four different urban contexts around the world are taken in account. • Three sectors are investigated: energy, mobility and built environment. • A consumption-based emission accounting method is used to assess the effective impact of cities. • Impacts of different GHG emission reduction interventions are evaluated for each city. [ABSTRACT FROM AUTHOR]

The United Nations Framework Convention on Climate Change (UNFCCC) sets an overall framework for intergovernmental efforts to tackle the challenge posed by climate change. Besides the “flexibility mechanisms” defined by the Kyoto Protocol to lower the overall costs of achieving their emissions targets, The Voluntary Green House Gases (GHG) reduction projects can have a lead role in GHG reduction in “non Emissions Trading System ETS sectors”. Nowadays, the voluntary market is characterised by critical aspects, such as fragmentation, lack of accounting, monitoring and validation rules that have led to the low spread of voluntary emission reduction projects developed by local authorities in the European Union despite their high potentiality. The aim of this paper is to test the applicability of voluntary emission reduction projects in the public sector following a homogeneous and consistent pattern. A research has been performed at local level on 143 voluntary emission reduction projects implemented by Public Administrations in Northern and Central Italy in renewable energy, energy efficiency and transport sectors. The applicable standards and methodologies have been checked and the case studies have been analysed though a three-step process: Preliminary additionality assessment; Projects selection; Validation of the selected project. The assessment shows that energy efficiency projects, once overcoming additionality issues, are the most promising for public entities while renewable energy and transport projects resulted to be mainly affected by double counting problems and lack of reliable methodologies. [ABSTRACT FROM AUTHOR]

[Display omitted] • Assessment of water-energy-food nexus in the agri-food sector. • Application of a life-cycle approach to different agricultural practices of crops. • Development of integrated water-energy-food-climate (WEFC) indicator based on LCA. • A unique indicator allows to identify the optimal agricultural practice of crop cultivation. • Results help to improve crop planning including energy and water requirements. The water-energy-food (WEF) nexus is the established framework to account for the three interlinked global security concerns of access to water, sustainable energy, and food security. Despite its outstanding relevance, a standardized methodology for quantifying the nexus and the related interconnections is still missing. Nowadays, life-cycle assessment (LCA) has been promoted as a key tool for quantifying the environmental impacts within WEF nexus although the normalization and weighting procedures require further investigations. The aim of the study is to develop an integrated water-energy-food-climate (WEFC) indicator adopting a life-cycle approach and to test its application in the agri-food sector, in order to pave the way for a decision-support tool to decision-makers. After selecting the relevant impact categories, a multi-variable optimization was carried out seeking the "best compromise" between water, energy, food, and climate issues. Then, a comparison-oriented analysis was performed to further examine the WEFC performances of the analyzed crops (tomato, corn, and pea) within an Italia case study. Overcoming the discrepancies that arise in the comparison of single environmental impact categories, the single WEFC indicator allowed to define tomato cultivation in Northern Italy by lateral infiltration, pea cultivation by pivot, and corn cultivation by pivot as the best trade-off scenarios for the analyzed sample. In this framework, the identification of best management scenarios is achieved by exploiting the potential synergies and the rational use of available resources, while the single indicator offers easy-to-read results for supporting decision makers. [ABSTRACT FROM AUTHOR]

Abstract The sun is considered to be one of the most environmentally sound sources of clean and renewable energy. Nevertheless, new hybrid solar plants - combining solar power with another source of energy - have never been compared to traditional solar technologies. Therefore, the aim of this work is to compare the potential environmental impact of a 100 kWp photovoltaic plant (PV) with a 100 kW hybrid solar-gas turbine system (SHGT) using a life cycle assessment methodology. To the best of our knowledge, this type of comparison is the first of its kind. The analysis is performed considering three different scenarios for the SHGT. Additionally, a deep sensitivity analysis is undertaken, focusing on those parameters that mostly influence the outcomes. The results highlight that, using the currently available technology, PV resulted to be the best environmental choice, with greenhouse gas (GHG) emission of 0.043 kg CO 2eq /kWh. SHGT plant emissions resulted to be higher, equal to 0.236 kg CO 2eq /kWh when running at nominal power 12 h/day, mainly due to the fuel contribution. However, improvements in receiver technology could make it possible to reach higher receiver outlet temperatures and consequently save fuel, reducing the overall environmental impact. Moreover, replacing the natural gas used as turbine running fuel with solar radiation leads to a reduction in GHG emissions, which become comparable to PV plant gases. Highlights • PV are a better environmental solution in comparison with SHGT. • The location of plants has a high influence on the final results. • Sizing of the heliostat field is very important to ensure good solar performance. • SHGT systems will improve their environmental scores whit technology enhancements. [ABSTRACT FROM AUTHOR]

Through the combination of Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) in a dedicated toolbox, the aim of this paper is to evaluate both potential environmental impacts and potential costs of the operation of a 230 kW Solid Oxide Fuel Cell (SOFC) system. LCA and LCC methodologies have been here applied for a comparison with a conventional technology, i.e. Micro Gas Turbine (MGT) for distributed power generation applications. A contribution analysis for the SOFC system fuelled with natural gas, reveals that the fuel supply is responsible of a relevant share of the environmental impact. The same system, fed with biogas, shows environmental benefits on global and regional impact categories, depending on the power energy mix used during the digestion process. For both SOFC and MGT systems, the life cycle hotspots are identifiable in the operation stage for the global warming category, and in the fuel supply stage for all the remaining impact categories. The LCA–LCC comparison between SOFC and MGT systems, based on a toolbox embedding a set of 8 sustainability indicators for decision making, shows that the SOFC system presents environmental and economic benefits in a life cycle perspective, particularly for household application. However, cost results to be the most sensitive bottle-neck for benchmarking with traditional energy systems. Therefore, the SOFC system is preferable to the conventional MGT technology when the sustainability of investment cost is demonstrated, whilst a wide advantage in environmental performance along the life cycle has been proved. [ABSTRACT FROM AUTHOR]

[Display omitted] • Precision agriculture and life cycle approach are combined to assess vegetable crops. • A cradle to grave analysis is performed to highlight hotspots of agricultural phase. • The water-energy-food nexus of bean, pea, sweet corn and tomato is analysed. • Optimal combination of ideotypes and crop management are evaluated. The increase in world population and the resulting demand for food, water and energy are exerting increasing pressure on soil, water resources and ecosystems. Identification of tools to minimise the related environmental impacts within the food–energy–water nexus is, therefore, crucial. The purpose of the study is to carry out an analysis of the agri-food sector in order to improve the energy-environmental performance of four vegetable crops (beans, peas, sweet corn, tomato) through a combination of precision agriculture (PA) and life cycle assessment (LCA). Thus, PA strategies were identified and a full LCA was performed on actual and future scenarios for all crops in order to evaluate the benefits of a potential combination of these two tools. In the case study analysed, a life cycle approach was able to target water consumption as a key parameter for the reduced water availability of future climate scenarios and to set a multi-objective function combining also such environmental aspects to the original goal of yield maximisation. As a result, the combination of PA with the LCA perspective potentially allowed the path for an optimal trade-off of all the parameters involved and an overall reduction of the expected environmental impacts in future climate scenarios. [ABSTRACT FROM AUTHOR]