O desenvolvimento sustentável e a própria sobrevivência da humanidade dependem da compatibilização da demanda por recursos energéticos com as limitações ambientais e necessidades humanas. Dessa maneira, torna-se fundamental compreender e mensurar a sustentabilidade energética. Para tanto, esse trabalho vale-se de princípios da economia ecológica e do planejamento integrado de recursos para identificar e analisar os fatores que afetam a sustentabilidade energética de um dado sistema. A partir desses fatores são definidos indicadores de sustentabilidade, os quais compõem uma metodologia concebida para avaliar o grau de sustentabilidade da produção de energia. Tal metodologia é testada em um estudo de caso da matriz elétrica paulista, a qual mostrou um nível próximo da sustentabilidade, mas com a necessidade de aprimoramentos. Por fim, são feitas reflexões sobre a robustez, a flexibilidade e as limitações da metodologia proposta, assim como recomendações para ajustes da composição da matriz estudada com o propósito de torná-la mais sustentável. / Sustainable development and the very survival of humanity depends on the compatibility of the demand for energy resources with environmental constraints and human needs. Thus, it is essential to understand and define metrics for energy sustainability. For that reason, this work draws on principles of ecological economics and integrated resource planning to identify and analyze the factors affecting energy sustainability of a given system. From these factors are defined sustainability indicators, which are the foundations for a methodology designed to assess the degree of sustainability of energy production. The methodology is tested on a case study of the electricity matrix of the State of Sao Paulo, which is close to a sustainable level even though requiring improvements in some aspects. Finally, reflections on the sturdiness, flexibility and limitations of the proposed methodology, as well as recommendations for adjustments in the composition of the case study matrix in order to make it more sustainable are made.

O desenvolvimento sustentável e a própria sobrevivência da humanidade dependem da compatibilização da demanda por recursos energéticos com as limitações ambientais e necessidades humanas. Dessa maneira, torna-se fundamental compreender e mensurar a sustentabilidade energética. Para tanto, esse trabalho vale-se de princípios da economia ecológica e do planejamento integrado de recursos para identificar e analisar os fatores que afetam a sustentabilidade energética de um dado sistema. A partir desses fatores são definidos indicadores de sustentabilidade, os quais compõem uma metodologia concebida para avaliar o grau de sustentabilidade da produção de energia. Tal metodologia é testada em um estudo de caso da matriz elétrica paulista, a qual mostrou um nível próximo da sustentabilidade, mas com a necessidade de aprimoramentos. Por fim, são feitas reflexões sobre a robustez, a flexibilidade e as limitações da metodologia proposta, assim como recomendações para ajustes da composição da matriz estudada com o propósito de torná-la mais sustentável. / Sustainable development and the very survival of humanity depends on the compatibility of the demand for energy resources with environmental constraints and human needs. Thus, it is essential to understand and define metrics for energy sustainability. For that reason, this work draws on principles of ecological economics and integrated resource planning to identify and analyze the factors affecting energy sustainability of a given system. From these factors are defined sustainability indicators, which are the foundations for a methodology designed to assess the degree of sustainability of energy production. The methodology is tested on a case study of the electricity matrix of the State of Sao Paulo, which is close to a sustainable level even though requiring improvements in some aspects. Finally, reflections on the sturdiness, flexibility and limitations of the proposed methodology, as well as recommendations for adjustments in the composition of the case study matrix in order to make it more sustainable are made.

Brown macroalgae or brown seaweed is a promising source of ethanol that may avoid the challenges of arable land use, water use, lignin content, and the food vs. fuel debate associated with first generation and cellulosic ethanol sources; however, this promise is challenged by seaweed’s high water content, high ash content, and natural composition fluctuations. Notably, lifecycle studies of seaweed ethanol are lacking in the literature. To address this gap, a well-to-wheel model of ethanol production from farmed brown seaweed was constructed and applied to the case of Saccharina latissima farming in British Columbia (BC), Canada, to determine energy return on energy invested (EROI), carbon intensity (CI), and near shore seaweed farming production potential for seaweed ethanol and to examine the production cost of seaweed ethanol. Seaweed farming and ethanol production were modeled based on current BC farming methods and the dry grind corn ethanol production process; animal feed was included as an ethanol co-product, and co-product credits were considered. A seaweed ethanol yield calculation tool that accounts for seaweed composition was proposed, and a sensitivity study was done to examine case study data assumptions. In the case study, seaweed ethanol had lower CI than sugarcane, wheat, and corn ethanol at 10.1 gCO2e/MJ, and it had an EROI comparable to corn ethanol at 1.78. Seaweed ethanol was potentially profitable due to significant revenue from animal feed sales; however, the market for seaweed animal feed was limited by the feed’s high sodium content. Near shore seaweed farming could meet the current demand for ethanol in BC, but world near shore ethanol potential is likely an order of magnitude lower than world ethanol production and two orders of magnitude lower than world gasoline production. Composition variation and a limited harvest season make solar thermal or geothermal seaweed drying and storage necessary for ethanol production in BC. Varying seaweed composition, solar thermal drying performance, co-product credits, the type of animal feed produced, transport distances, and seaweed farming performance in the sensitivity study gave an EROI of over 200 and a CI of -42 gCO2e/MJ in the best case and an EROI of 0.64 and CI of 33 gCO2e/MJ in the worst case. Co-product credits and the type of animal feed produced had the most significant effect overall, and the worst cases of seaweed composition and solar thermal seaweed drying system performance resulted in EROI of 0.64 and 1.0 respectively. Brown seaweed is concluded to be a potentially profitable source of ethanol with climate benefits that surpass current ethanol sources; however, additional research into seaweed animal feed value, co-product credits, large scale seaweed conversion, and the feasibility of solar thermal or geothermal seaweed drying is required to confirm this conclusion. / Graduate