Percorrer por autor "SOUSA, ANA CATARINA COSTA"
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- O microreator NetMIX como potencial tecnologia de purificação de biogás em Estações de Tratamento de Águas Residuais: Análise de Ciclo de VidaPublication . SOUSA, ANA CATARINA COSTA; Morais, Simone BarreiraIn this study, a life cycle assessment was performed that compares the impacts associated with the joint production of two fuel alternatives to fossil natural gas by two different production pathways. The production of biomethane (BioCH4) and synthetic natural gas (SNG) for injection into the natural gas distribution network is carried out from biogas obtained from sewage sludge, a residue from wastewater treatment plants, by two pathways that differ in the upgrading technology employed in the separation of methane from carbon dioxide. One of the pathways separates these compounds through a membrane (MP), the most commercially applied technology, and the other captures carbon dioxide through hydrate formation in a microreactor under development, the NetMIX microreactor (HBGtS). In each of these pathways, a scenario of the impact of the production of solely biomethane was also evaluated. The determination of the total potential production of SNG and biomethane in Portugal was also an objective of the study as well as its associated impact and the effect that the use of renewable sources of electricity, solar and wind energy, has on the environmental impact of production. The life cycle assessment was prepared by applying the characterization factors included in the ReCiPe 2016 method, available in the SimaPro software, using seven of the categories provided by the method. For all the analyzed categories, except water consumption and global warming potential, the highest impacts are attributed to the scenarios producing both BioCH4 and SNG. For the scenarios producing biomethane, the heavier impact is observed in the pathway using HBGtS as the upgrading unit. The global warming potentials show greater impacts on the scenario where biomethane and synthetic natural gas are produced, scenarios 1 and 3, and a heavier contribution from the Electrolysis process, accounting 76.2% and 71.0% of total global warming potentials, respectively for the pathway using MP and HBGtS as upgrading technology. When only BioCH4 is the final product, scenarios 2 and 4, a reduction of impacts is observed in the MP upgrading pathway, and an increase is observed on the HBGtS upgrading pathway, in comparison with the other scenario in the respective pathway. The HBGtS upgrading unit burden contributes with 11.4% and 74.5% of the total global warming potentials, respectively in scenarios 3 and 4, with electricity consumption, 72% of process contribution, and with emissions associated with treatment of the wastewater that leaves the process, 28%. The MP upgrading unit, in turn contributes to total impact of about 4.5% and 32.9%, in scenarios 1 and 2, solely from electric power fed to the system. When assumed a water recycling system, HBGtS’ electricity burden still makes its impacts prevail over the use of membrane separation, opposing 0.0077 and 0.0035 kg CO2/MJ. In order to turn the HBGtS technology into a more competitive approach becomes crucial the use of promoters in hydrate formation that aim to reduce the operating pressure and so the energy consumption. Also, a more precise assessment of the information collected to the upgrading technologies inventory may be a future work to be done, in order to mitigate the uncertainty aspects and allow a more precise and fair comparison. Some uncertainty aspects are the extrapolation of the Aspen simulations data, which assumes the best possible case, for the HBGtS upgrading unit. Concerning the MP upgrading unit, the different flow and composition from where the data was collected, and the not consideration of the membrane lifetime. Regarding the MP upgrading unit, the scale and composition disparity towards the case study, the non-inclusion of aspects related to the used membrane materials as well as its lifetime and maintenance requirements. The lowest impacts were obtained for the MP pathway with a global warming potential of 0.08 kg CO2/MJ of BioCH4+SNG and 0.03 kg CO2/MJ for BioCH4 production, the latter revealing the pathway with the best environmental performance per energy unit of final product. In Portugal, the biomethane production potential is 175,000 MJ/h which results in a global warming potential in the MP pathway of 13.8 t kg CO2/h for the scenario producing BioCH4 and SNG and for the BioCH4 production is 6.0 t kg CO2/h. The use of solar and wind-sourced electricity causes a 62% and 73% reduction in the global warming potentials respectively for the MP pathway scenario 1, and 61% and 70% for the HBGtS pathway, scenario 3. The use of renewable electric energy in the electrolysis process shows its advantages.