Life Cycle Sustainability Assessment of Electricity Generation Systems in Portugal

Abstract

The following thesis presents a multidimensional life cycle sustainability assessment (LCSA) study; carried out to estimate and compare the environmental and socioeconomic impacts associated with six, key electricity generation systems in Portugal namely; coal, natural gas, hydro (large and small), wind, and photovoltaic (PV). In addition to updating the models (i.e. data and assumptions) and impact assessment methods used in an existing life cycle assessment (E-LCA) for the Portuguese context (Garcia et al. 2014), the current study also broadens its scope; assessing critical water use, and applies relevant indicators to account for socioeconomic impacts. The life cycle assessment (E-LCA) methodology was used to quantify environmental impacts in: metal depletion, fossil fuel depletion, non-renewable primary energy, global warming potential, ozone depletion, terrestrial acidification, freshwater eutrophication, aquatic acidification, freshwater ecotoxicity; as well as human health impacts in toxicity (carcinogenic and non-carcinogenic). In addition to the water use impacts associated to quality, the water scarcity footprint of each system was estimated using the AWARE method – to assess the water use impact related to quantity. For socioeconomic impacts, a range of empirical methods, and relevant literature were used to estimate impacts in: employment provision (domestic and total), dependence on fossil fuels, capacity factor, and levelised cost of electricity. Within most of the environmental categories, generation based on coal was estimated to have the most negative (i.e. highest) impacts, apart from: metal depletion (wind), ozone depletion (natural gas), water scarcity footprint (large hydro) and freshwater ecotoxicity (PV). For socioeconomic categories, there was more variability as to which system produced the most positive or negative impacts. Coal – previously the worst-performing (environmentally) was estimated to generate the most total employment; had the highest capacity factor; and the second-lowest levelised cost. While PV was estimated to generate the most domestic employment, it had the lowest capacity factor, and the highest non-carcinogenic toxicity towards humans. Overall, small hydro systems appeared to be the most sustainable; both environmentally and socioecomically. The LCSA methodology (as applied to the current study) is beneficial for holistically considering and quantifying the wider life cycle impacts of systems; across the boundaries of traditional dimensions of sustainability. As a decision support tool, LCSA has provided an overview of the sustainability performance of key electricity generation systems used in Portugal; as well as highlighted areas of either significant negative impact – where improvements can be made; or positive impact – where opportunities can be exploited. In order to gain the optimum benefit from the available systems or options, it is often necessary for decision makers to consider different trade-offs, depending on the varying (and at times conflicting) priorities of relevant stakeholders.

The following thesis presents a multidimensional life cycle sustainability assessment (LCSA) study; carried out to estimate and compare the environmental and socioeconomic impacts associated with six, key electricity generation systems in Portugal namely; coal, natural gas, hydro (large and small), wind, and photovoltaic (PV). In addition to updating the models (i.e. data and assumptions) and impact assessment methods used in an existing life cycle assessment (E-LCA) for the Portuguese context (Garcia et al. 2014), the current study also broadens its scope; assessing critical water use, and applies relevant indicators to account for socioeconomic impacts. The life cycle assessment (E-LCA) methodology was used to quantify environmental impacts in: metal depletion, fossil fuel depletion, non-renewable primary energy, global warming potential, ozone depletion, terrestrial acidification, freshwater eutrophication, aquatic acidification, freshwater ecotoxicity; as well as human health impacts in toxicity (carcinogenic and non-carcinogenic). In addition to the water use impacts associated to quality, the water scarcity footprint of each system was estimated using the AWARE method – to assess the water use impact related to quantity. For socioeconomic impacts, a range of empirical methods, and relevant literature were used to estimate impacts in: employment provision (domestic and total), dependence on fossil fuels, capacity factor, and levelised cost of electricity. Within most of the environmental categories, generation based on coal was estimated to have the most negative (i.e. highest) impacts, apart from: metal depletion (wind), ozone depletion (natural gas), water scarcity footprint (large hydro) and freshwater ecotoxicity (PV). For socioeconomic categories, there was more variability as to which system produced the most positive or negative impacts. Coal – previously the worst-performing (environmentally) was estimated to generate the most total employment; had the highest capacity factor; and the second-lowest levelised cost. While PV was estimated to generate the most domestic employment, it had the lowest capacity factor, and the highest non-carcinogenic toxicity towards humans. Overall, small hydro systems appeared to be the most sustainable; both environmentally and socioecomically. The LCSA methodology (as applied to the current study) is beneficial for holistically considering and quantifying the wider life cycle impacts of systems; across the boundaries of traditional dimensions of sustainability. As a decision support tool, LCSA has provided an overview of the sustainability performance of key electricity generation systems used in Portugal; as well as highlighted areas of either significant negative impact – where improvements can be made; or positive impact – where opportunities can be exploited. In order to gain the optimum benefit from the available systems or options, it is often necessary for decision makers to consider different trade-offs, depending on the varying (and at times conflicting) priorities of relevant stakeholders.