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Esta dissertação foi realizada no âmbito da unidade curricular Dissertação/Projeto/ Estágio, que integra o segundo ano do Mestrado em Energias Sustentáveis do Instituto Superior de Engenharia do Porto. A dissertação foi desenvolvida em ambiente académico, integrada no projeto PhytoEnergy. A contaminação do solo é um problema atual, principalmente quando esta contaminação é devida a metais pesados. A fim de promover a descontaminação dos solos, têm sido estudadas alternativas menos agressivas e economicamente viáveis de remediação dos mesmos. Para o efeito, como tecnologia alternativa surge a fitorremediação. Esta técnica consiste na utilização de plantas com o intuito de diminuir a toxicidade e a concentração dos contaminantes presentes no solo ou, até mesmo, na água ou no ar. De forma a avaliar a sustentabilidade da utilização do óleo de girassol proveniente de solos contaminados para a produção de biodiesel, realizou-se um estudo de avaliação de ciclo de vida (ACV). O estudo de ACV realizado no presente trabalho, teve como objetivo avaliar o desempenho ambiental de biodiesel produzido a partir de óleo de girassol de fitorremediação de solos contaminados com zinco e cádmio, a fim de averiguar se a utilização de sementes cultivadas em solos contaminados constitui uma boa alternativa para a valorização da biomassa resultante da fitorremediação dos referidos solos. Para a aplicação da metodologia de ACV, foram utilizadas as normas ISO 14040:2006 e ISO 14044:2006, as quais serviram de guia para o desenvolvimento do trabalho prático. O estudo de ACV realizado seguiu uma abordagem cradle-to-gate e a unidade funcional foi definida como 1 kg de biodiesel. De forma a quantificar os impactes ambientais, utilizou-se o método ILCD 2011 Midpoint+ V1.10 / EC-JRC Global, equal weighting, no qual foram selecionadas dez categorias de impacte ambiental consideradas relevantes para o estudo. Consideraram-se quatro cenários para o estudo: cenário base, o qual considerou a utilização do Mix energético nacional como fonte de energia e hexano 100% virgem para extração do óleo; cenário 1, o qual considerou a utilização de energia renovável fotovoltaica e hexano 100% virgem para extração do óleo; cenário 2, o qual considerou a utilização do Mix energético nacional como fonte de energia com hexano 80% reciclado e 20% virgem para extração do óleo; cenário 3, no qual foi combinada a utilização de energia renovável fotovoltaica e hexano 80% reciclado e 20% virgem para extração do óleo. Conclui-se que os impactes gerados na produção de biodiesel proveniente de solo industrial (contaminado), no máximo são cerca de 35% superiores em relação aos do solo de controlo. A conclusão é semelhante em todos os cenários apresentados. De todas as etapas de produção de biodiesel, o cultivo revelou ser a que contribuiu com os maiores impactes. Os valores obtidos no cultivo não se alteraram nos diferentes cenários por dependerem apenas do consumo de água. Desta etapa, destacam-se os maiores impactes ambientais associados às categorias de impacte alterações climáticas (CC) e ecotoxicidade da água doce (FEC), as quais apresentam valores de 1,16E+02 kg CO2 eq e 1,25E+03 CTUe para o solo de controlo e 1,56E+02 kg CO2 eq e 1,67E+03 CTUe para o solo industrial, respetivamente. Quanto às restantes etapas envolvidas na produção de biodiesel, em todos os cenários, as categorias que registaram maiores impactes as alterações climáticas e a ecotoxicidade da água doce. Neste estudo, determinou-se, ainda, para ambos os solos, a importância relativa dos diferentes materiais utilizados ao longo do ciclo de vida, para o cenário base e para o cenário em que se considerou a utilização de hexano 80% reciclado sem alteração da fonte energética. Desta análise, conclui-se que em ambos os cenários, o consumo de água provoca os maiores impactes, seguindo-se o hexano. Fazendo uma análise geral, comparativamente ao cenário base, os restantes cenários apresentam impactes menores em quase todas as categorias de impacte. Deste modo, de forma a garantir a melhor utilização do solo industrial, o cenário que deve ser tomado em consideração para originar os menores impactes ambientais, é o que combina a mudança do mix energético nacional atual com a alteração do solvente hexano virgem para hexano 20% virgem + 80% reciclado, portanto, o último cenário. Para concluir, é de esperar que a utilização de girassol proveniente de fitorremediação de solos contaminados na produção de biodiesel seja uma boa alternativa para evitar a utilização desnecessária de terras aráveis e para promover a reutilização de solos sem utilidade, permitindo uma valorização adicional da biomassa resultante de fitorremediação de solos contaminados, enquanto os solos não puderem ser utilizados para culturas alimentares.
This dissertation was performed in the scope of the curricular unit Dissertation/Project/Internship, which integrates the second year of the Sustainable Energies Master degree from Instituto Superior de Engenharia do Porto. The dissertation was developed in an academic environment, integrated in the PhytoEnergy project. Soil contamination is a current problem, especially when this contamination is caused by heavy metals. In order to promote soil decontamination, less aggressive and economically feasible alternatives for soil remediation have been studied. For this purpose, the concept of phytoremediation emerges as an alternative. This technique consists in the use of green plants with the purpose of decreasing the toxicity and the concentration of soil, water or air contaminants. The application of phytoremediation allows contaminated soils to be useful again, promoting sustainability concept. In order to evaluate the sustainability of using phytoremediated soils for biodiesel production, a life cycle assessment (LCA) study was conducted. LCA is considered a suitable tool for sustainability evaluation, which allows the quantification of environmental impacts caused by a specific product/process, helping in decision making in the selection of products or processes that have less impact on the environment. Therefore, the LCA study performed in this work intended to characterize the environmental performance of the different stages of biodiesel production, in order to investigate if the use of seeds grown in phytoremediated soil are a good alternative for the reuse of contaminated land. To implement the LCA methodology, the ISO 14040:2006 and ISO 14044:2006 standards were used as a guide for the development of the practical work. The performed Life Cycle Assessment study followed a cradle-to-gate approach, where all life cycle steps were considered from raw material cultivation to the obtaining of the final product. The functional unit was defined as 1 kg of biodiesel. In order to quantify the environmental impacts, the ILCD 2011 Midpoint+ V1.10 / EC-JRC Global, equal weighting method was used, in which ten relevant environmental impact categories for the study were selected. Four scenarios were considered for the study: baseline scenario, which considered the use of the national energy mix as the energy source and 100% virgin hexane for oil extraction; scenario 1, which considered the use of photovoltaic renewable energy and 100% virgin hexane for oil extraction; scenario 2, which considered the use of the national energy mix as the energy source with 80% recycled and 20% virgin hexane for oil extraction; scenario 3, in which the use of photovoltaic renewable energy and 80% recycled and 20% virgin hexane for oil extraction was combined. From this study, it can be concluded that the impacts generated by biodiesel from industrial soil, in all the presented scenarios, differ at most about 35% compared to the control soil, and the impacts were always higher in the contaminated soil. Of all the biodiesel production stages, cultivation was the one that produced the greatest impacts. The values obtained in the cultivation did not change in the different scenarios because they only depend on water consumption. From this stage, the biggest environmental impacts associated with the impact categories of climate change (CC) and freshwater ecotoxicity (FEC) stand out, with values of 1.16E+02 kg CO2 eq and 1.25E+03 CTUe for the control soil and 1.56E+02 kg CO2 eq and 1.67E+03 CTUe for the industrial soil, respectively. As for the remaining steps involved in biodiesel production, it was unanimous that the categories that caused the most impacts were those associated with climate change and freshwater ecotoxicity. In this study, it was also determined, for both soils, the relative importance of the different materials used throughout the life cycle, for the baseline scenario and considering the use of 80% recycled hexane without changing the energy source. From this analysis, it can be concluded that in both scenarios, water causes the greatest impacts, followed by hexane as a contributing material. Making an overall analysis, compared to the baseline scenario, the other scenarios present lower impacts in almost all impact categories. In order to ensure the best use of industrial soil, the scenario that should be taken into consideration to cause the lowest environmental impacts, is the one that compiles the change of the national energy mix with the change of the solvent hexane 100% virgin for recycled hexane, therefore, the last scenario. To conclude, it can be expected that the use of sunflower from phytoremediation of contaminated soils in the production of biodiesel is a good alternative to avoid unnecessary use of arable land and to promote the reuse of unused soils, allowing an additional valorization of biomass resulting from phytoremediation of contaminated soils, while the soils cannot be used for food crops.
This dissertation was performed in the scope of the curricular unit Dissertation/Project/Internship, which integrates the second year of the Sustainable Energies Master degree from Instituto Superior de Engenharia do Porto. The dissertation was developed in an academic environment, integrated in the PhytoEnergy project. Soil contamination is a current problem, especially when this contamination is caused by heavy metals. In order to promote soil decontamination, less aggressive and economically feasible alternatives for soil remediation have been studied. For this purpose, the concept of phytoremediation emerges as an alternative. This technique consists in the use of green plants with the purpose of decreasing the toxicity and the concentration of soil, water or air contaminants. The application of phytoremediation allows contaminated soils to be useful again, promoting sustainability concept. In order to evaluate the sustainability of using phytoremediated soils for biodiesel production, a life cycle assessment (LCA) study was conducted. LCA is considered a suitable tool for sustainability evaluation, which allows the quantification of environmental impacts caused by a specific product/process, helping in decision making in the selection of products or processes that have less impact on the environment. Therefore, the LCA study performed in this work intended to characterize the environmental performance of the different stages of biodiesel production, in order to investigate if the use of seeds grown in phytoremediated soil are a good alternative for the reuse of contaminated land. To implement the LCA methodology, the ISO 14040:2006 and ISO 14044:2006 standards were used as a guide for the development of the practical work. The performed Life Cycle Assessment study followed a cradle-to-gate approach, where all life cycle steps were considered from raw material cultivation to the obtaining of the final product. The functional unit was defined as 1 kg of biodiesel. In order to quantify the environmental impacts, the ILCD 2011 Midpoint+ V1.10 / EC-JRC Global, equal weighting method was used, in which ten relevant environmental impact categories for the study were selected. Four scenarios were considered for the study: baseline scenario, which considered the use of the national energy mix as the energy source and 100% virgin hexane for oil extraction; scenario 1, which considered the use of photovoltaic renewable energy and 100% virgin hexane for oil extraction; scenario 2, which considered the use of the national energy mix as the energy source with 80% recycled and 20% virgin hexane for oil extraction; scenario 3, in which the use of photovoltaic renewable energy and 80% recycled and 20% virgin hexane for oil extraction was combined. From this study, it can be concluded that the impacts generated by biodiesel from industrial soil, in all the presented scenarios, differ at most about 35% compared to the control soil, and the impacts were always higher in the contaminated soil. Of all the biodiesel production stages, cultivation was the one that produced the greatest impacts. The values obtained in the cultivation did not change in the different scenarios because they only depend on water consumption. From this stage, the biggest environmental impacts associated with the impact categories of climate change (CC) and freshwater ecotoxicity (FEC) stand out, with values of 1.16E+02 kg CO2 eq and 1.25E+03 CTUe for the control soil and 1.56E+02 kg CO2 eq and 1.67E+03 CTUe for the industrial soil, respectively. As for the remaining steps involved in biodiesel production, it was unanimous that the categories that caused the most impacts were those associated with climate change and freshwater ecotoxicity. In this study, it was also determined, for both soils, the relative importance of the different materials used throughout the life cycle, for the baseline scenario and considering the use of 80% recycled hexane without changing the energy source. From this analysis, it can be concluded that in both scenarios, water causes the greatest impacts, followed by hexane as a contributing material. Making an overall analysis, compared to the baseline scenario, the other scenarios present lower impacts in almost all impact categories. In order to ensure the best use of industrial soil, the scenario that should be taken into consideration to cause the lowest environmental impacts, is the one that compiles the change of the national energy mix with the change of the solvent hexane 100% virgin for recycled hexane, therefore, the last scenario. To conclude, it can be expected that the use of sunflower from phytoremediation of contaminated soils in the production of biodiesel is a good alternative to avoid unnecessary use of arable land and to promote the reuse of unused soils, allowing an additional valorization of biomass resulting from phytoremediation of contaminated soils, while the soils cannot be used for food crops.
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Keywords
Avaliação de ciclo de vida Biodiesel Biomassa de girassol Fitorremediação Metais pesados Solos contaminados Life cycle assessment; Heavy metal contaminated soil Phytoremediation Sunflower biomass