ISEP – DEQ – Comunicações em eventos científicos
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- A life cycle inventory of microalgae-based biofuels production in an industrial plant conceptPublication . Branco-Vieira, M.; Costa, D.; Mata, T.M.; Martins, A.A.; Freitas, M.A.V.; Caetano, NídiaMicroalgae have been reported as a promising alternative for biofuels production. However, the use of microalgae for biofuels is still a challenge due to the intense energy use and the generation of a significant amount of biomass residues in the process. In order to analyze the environmental impacts of different technological processes for the production of biodiesel from microalgae, several studies have been published making use of the Life Cycle Assessment (LCA) methodology, which allows the recognition of the process bottlenecks and supports the identification of alternatives for a more efficient use of the feedstock. Therefore, in this study, a Life Cycle Inventory (LCI) is compiled, based on real pilot-scale process data, which was scaled-up to a microalgae biomass industrial plant for biofuel production. Values of energy, nutrients, water, and materials consumption are used to create an inventory of inputs and outputs for biomass cultivation and biodiesel production, in order to acquire data to conduct a complete LCA modeling in future studies. According to this model, to produce 1 kg of biodiesel it is necessary about 12 kg of dried algae biomass. This study supports the decision-making process in biofuel production to promote the development of sustainable pilot and large-scale algae-based industry, through the identification of critical factors.
- Co-gasification of glycerol/fat mixtures in a downflow fixed bed reactor: Preliminary resultsPublication . Almeida, A.; Pilão, Rosa Maria; Ramalho, Elisa; Ribeiro, A.M.; Pinho, CarlosThe aim of this work was to assess the technical viability of glycerol/fat co-gasification. The gasification performance was studied in a downflow fixed bed reactor using steam as oxidizing agent. Tests were performed with a mixture of 10% of fat and 52% of water, and the effect of temperature was evaluated in the 800 ºC to 950 ºC range. Samples of dry gas from the gasifier were collected and analysed by gas chromatography in order to determine the CO, CO2, CH4 and H2 content. The results revealed that the co-gasification of glycerol/fat mixtures seems to be a feasible technical option. Best results of the gasification parameters were obtained at the highest tested temperature, 950 °C.
- Flocculation of Arthrospira maxima for improved harvestingPublication . Caetano, Nídia; Martins, A.A.; Gorgich, M.; Gutiérrez, D.M.; Ribeiro, T.J.; Mata, T.M.The environmental impacts associated with the burning of fossil fuels coupled with growing concerns about security of energy supply, motivated the search for more sustainable forms of energy production, among which came microalgae for biofuels production. However, the commercial production of microalgae biofuels is still not competitive compared to fossil fuels, as it is necessary to solve some process bottlenecks, among which biomass harvesting, that is the focus of this work. Hence, this work intends to study the harvesting of microalga Arthrospira maxima through flocculation by pH variation and/or addition of CaCl2 as flocculant. Thus, it is described the effect of pH variation (in the range 6 to 12), followed by the addition of flocculant, on the harvesting efficiency. Results show that by pH increase over 10 using NaOH, or by flocculation using CaCl2 at a concentration of 0.2-2.0 g/L and at a 1:30 ratio (v/v) of CaCl2/microalgae culture, it is possible to effectively harvest this microalga.
- Catalytic bi-reforming of methane for carbon dioxide ennoblementPublication . Cunha, Adelino F.; Mata, T.M.; Caetano, Nídia; Martins, A.A.; Loureiro, J.M.New processes that may reduce the net carbon emissions and contribute to a more circular economy are needed. Bi-reforming of methane (BRM) is a promising method for syngas production, with a hydrogen-to-carbon monoxide ratio of two in the reaction products, relevant for example when the purpose is methanol synthesis. In this work, reaction studies were carried out over a nickel-based catalyst varying the temperature (798–1123 K). Three main temperature zones have been identified; a low temperature zone where the conversion of carbon dioxide is almost null, a middle temperature range where steam reforming of methane (SRM) is dominant while the conversion of carbon dioxide via dry reforming of methane (DRM) is low, and finally a high temperature range where DRM becomes more significant. The results show that syngas can be successfully produced using this process. For the range of operating conditions studied, the carbon dioxide and methane conversions increase with temperature, reaching 40% and 100%, respectively at the largest temperature studied. However, the production of syngas in a molar ratio of 1:2 for CO-to-H requires the use of high temperatures. Most probably the nickel agglomerates on top of the -alumina support are responsible for the poor catalyst performance.
- Sustainability evaluation of a Portuguese “terroir” winePublication . Martins, A.A.; Costa, M.C.; Araújo, A.R.; Morgado, A.; Pereira, J.M.; Fontes, N.; Graça, A.; Caetano, Nídia; Mata, T.M.The challenges of sustainability are transversal to all human activities, and the wine sector has its own role to play in the march for a more sustainable development. The proper definition of the most adequate measures and/or policies must be based on an objective and quantitative evaluation of the sustainability of a product or process. In this work the sustainability of a “terroir” wine is assessed taking into account its life cycle and using the following indicators: carbon and water footprint, material intensity, solid waste generated, worker turnover rate, investment in H&S training and EBITDA. All indicators are expressed per functional unit of 0.75 L of wine. The evaluation used data from the company complemented with data/information from the literature or life cycle inventory databases. To account for climatic variability, data from three consecutive years was used. Average values of 3.51 kgCO2eq and 481.4 L per functional unit were obtained for the carbon and water footprint respectively, both values within the range of values reported in the literature.
- Slow pyrolysis of oil palm mesocarp fibres: Effect of operating temperaturePublication . Almeida, A. F.; Direito, D.; Pilão, Rosa Maria; Mayer, B.This study investigated the effect of temperature on the slow pyrolysis of oil palm mesocarp fibres. The biomass was characterized in terms of proximate and ultimate analysis, and its higher heating value (HHV) was 18.51 MJ/kg. For pyrolysis temperatures from 469 to 783°C, at a heating rate of 20°C/min, bio-char yield varied between 32.7% and 25.8%. Gas and liquid phases were analysed by gas chromatography and Fourier-Transform Infrared Spectrometry (FTIR), respectively. CO2 was the major gas produced for all temperatures (6.9 to 10.0mol/kg of biomass) and H2 concentration increased rapidly as the temperature rose (0.6 to 8.0 mol/kg of biomass). FTIR measurements show that the bio-oils contained alcohols, phenols, alkanes, alkenes, carboxylic acids, aldehydes and aromatic compounds. The HHV of both bio-chars (27.50 to 28.86 MJ/kg) and bio-oils (25.95 to 28.50 MJ/kg) were measured. Thermal decomposition of the fibres was also studied using thermogravimetric analysis.
- Life cycle assessment of a renewable energy generation system with a vanadium redox flow battery in a NZEB householdPublication . Gouveia, J.R.; Silva, E.; Mata, T.M.; Mendes, A.; Caetano, Nídia; Martins, A.A.Buildings are responsible for a significant part of the global energy consumption. Besides the need to improve their energy efficiency, new buildings also need to generate their own energy, preferably from renewable sources, to become more sustainable. As renewable energy generation is strongly dependent on the climatic conditions, energy storage must be considered when designing such a system. In this study, a cradle-to-grave life cycle assessment (LCA) study of a renewable energy generation system with a prototype Vanadium flow battery integrated in a Near Zero Energy Building (NZEB) is performed. A combined grid-connected PV and a solar thermal system generates the energy, and it was dimensioned to supply the annual energy needs of a household in Porto, Portugal considering the local climatic conditions. As an end of life scenario, it is assumed that the battery is dismantled and most of the materials are recycled. A functional unit of 1 kWh of supplied energy to the system was considered, and study results show that environmental impacts are reduced when the energy is produced onsite and the battery components are recycled or reused. A sensitivity analysis was conducted changing the household’s geographic location.
- Biofixation of CO2 emissions from natural gas combined cycle power plantPublication . Oliveira, Gisela M.; Caetano, Nídia; Mata, Teresa M.; Martins, António A.The growing impacts of climate change mainly due to the increasing emissions of GHG, especially carbon dioxide, has led to the development and implementation of specific strategies and policies to reduce them. Carbon capture and utilization (CCU) is currently seen as a good option, as it contributes to reduce the net carbon emissions and fulfil the goals of the Paris Agreement. This work analyses the economic potential of CO2 biofixation by microalgae from the exhaust gas of a Portuguese Natural Gas Combined Cycle (NGCC) power plant. Literature and real operational data are used, collected from reports of Portuguese power generation companies. A preliminary design and economic analysis of the carbon biofixation system was done. Results show that, although requiring a very large investment, the process is economically viable. In further studies a more in depth approach and detailed project combined with a sensitivity analysis, and a comparison with the chemical based CO2 fixation will be done.
- Pyrolysis of leather wastes from the footwear industry –preliminary resultsPublication . Direito, D.; Pilão, Rosa Maria; Crispim, Alfredo; Ribeiro, A.M.Most of the leather used by the footwear industry (more than 70%) is produced from skins and hides tanned with chromium sulphate [1]. The production of leather goods, especially shoes, gives rise to wastes that amount to 15 – 20% of the entry leather [2]. As an example, the European footwear industry generates between 1x105 to 2x105 tons per year of leather wastes [1]. In the last few years, various investigations have been carried out in order to find alternatives to the disposal of these residues in landfills. Several processes have been developed to treat the leather residues that include, among others, combustion, pyrolysis, chemical treatment (oxidation and hydrolysis) or direct application of the wastes [2]. Pyrolysis is the thermal degradation of wastes, in the presence of an inert atmosphere, producing a solid phase (biochar), a liquid phase (bio-oil) and a gas phase composed mainly of CO2, CO, CH4 and H2 [3]. Several authors have reported work on the pyrolysis of chromium tanned leather wastes [4, 5, 6]. [...]
- Comparison of different lipid extraction procedures applied to three microalgal speciesPublication . Gorgich, M.; Mata, T.M.; Martins, A.A.; Branco-Vieira, M.; Caetano, NídiaThe increase in the world’s energy demand has contributed to the emergence of new sustainable energy sources, such as microalgae, with their great potential to provide biofuels and other high value co-products for the food and health’s markets. However, current biorefinery methodologies are either too complex to extract the targeted components such as high-value products, or require solvents with toxicity for humans and the environment. This work aims to evaluate different lipid extraction approaches applied to three microalgal species: Chlorella zofingiensis, Phaeodactylum tricornutum, and Arthrospira platensis, while employing less toxic and more economical solvents for the lipids extraction. Experimental results showed a promising outcome to tune current biorefinery methodologies, enhancing product yield as well as decreasing potential hazards.