Browsing by Issue Date, starting with "2022-09"
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- Contribution to the Understanding of the Colour Change in Bluish-Grey LimestonesPublication . Silva, Teresa; De Oliveira, Daniel Pipa Soares; Veiga, JP; Lisboa, Jose; Carvalho, Jorge; Barreiros, M. Alexandra; Coutinho, ML; Salas-Colera, Eduardo; Vigário, RogérioABSTRACT: Bluish-grey limestones have been extensively used as ornamental stones for decoration purposes in buildings, as well as in works of art, and accordingly, have been the target of intense exploration. In Portugal, the Jurassic limestone massif known as the Macico Calcario Estremenho (MCE), has been the source of grey-coloured ornamental stones, namely the Azul Valverde (one of the most well-known bluish-grey limestones) and Atlantic Blue varieties, both of which may undergo colour changes in outdoor environments. In this sense, it is important to understand the sudden colour change from bluish-grey to yellow/beige in the same limestone block in a quarry, or even, what happens to the colour when polished limestone is placed outdoors. This study was undertaken using various techniques, namely XRF (X-ray fluorescence spectrometry), XRD (X-ray diffraction), SEM (scanning electron microscopy), DTA-TG (differential thermal analysis/thermogravimetry) and colourimetry. Synchrotron radiation was also used at the European Synchrotron Radiation Facility (ESRF, Grenoble, France) where XANES (X-ray Absorption Near Edge Structure) spectra at Fe K-edge were collected to ascertain the speciation state of Fe in different coloured zones of the limestone, previously checked by EDXRF (energy dispersive X-ray fluorescence). The presence of Fe2+ and Fe3+ are responsible for the greyish and yellow/brown colour, respectively. On the other hand, the UV radiation from the sun causes a quickened and severe bleaching/fading on the dark blue/grey polished limestone.
- Biodesulfurization biorefinery using Gordonia alkanivorans strain 1B: life cycle inventory of the integrated processPublication . Silva, Tiago; Silva, Carla; Paixão, Susana M.; Alves, LuísABSTRACT: High sulfur concentrations are a problem common to fossil fuels and derivatives (such as oil and coal), as well as many new generation fuels and biofuels (such as pyrolysis oils, syngas, biogas or even biodiesel). If the sulfur present in these fuels is released into the atmosphere it can result in SO2/SOx emissions, leading to environmental damage, and health issues. Transportation fuels have sulfur limits that go below 5000 ppm in ships, 3000 ppm in airplanes and 10 ppm in cars, and without treatment fuels can have several thousand ppm of sulfur. As such, they must be submitted to desulfurization, typically through a thermochemical process known as hydrodesulfurization, in which H2 is combined with the fuel at high temperatures and pressures, in the presence of metal catalysts. However, this process has significant environmental impacts. Usually, it depends on hydrogen and heat/steam produced from natural gas, totalizing 4.17 kg natural gas per 2.89 kg sulfur removed. It also involves high electricity and water consumption (approximately 2.9 kWh and 86.9 kg, respectively, per 2.89 kg sulfur removed). Furthermore, these impacts are greater for lower sulfur demands (Burgess & Brennan, 2001). Thus, there has been a search for alternative/complementary processes, one of which is biodesulfurization (BDS). It consists of the use of microorganism that consume the sulfur present in the fuels, at ambient temperature and pressure, without the need for metal catalysts. BDS still presents several bottlenecks, common to many microbial processes, such as low conversion rates and high production costs for the microbial biocatalyst. To surpass these limitations researchers have pursued different strategies: minimization/optimization of culture medium and culture conditions; employment of cheaper alternative nutrient sources; exploitation of added value products. Gordonia alkanivorans strain 1B is a bacterium known for its biodesulfurization properties. It has demonstrated several characteristics which make it interesting: it can perform BDS of different compounds, several of which extremely recalcitrant for the thermochemical process; it has very low nutritional needs; it can be cultivated on several alternative carbon sources; it has been shown to produce two different types of added value products: carotenoids and biosurfactants (Alves et al., 2015; Silva et al., 2020, 2022). Therefore, G. alkanivorans strain 1B is the ideal candidate for a biodesulfurization biorefinery, that simultaneously removes sulfur from fuels and produces carotenoids and biosurfactants.
- Agent-based model of citizen energy communities used to negotiate bilateral contracts in electricity marketsPublication . Algarvio, HugoABSTRACT: The worldwide targets for carbon-neutral societies increased the penetration of distributed generation and storage. Smart cities now play a key role in achieving these targets by considering the alliances of their demand and supply assets as local citizen energy communities. These communities need to have enough weight to trade electricity in wholesale markets. Trading of electricity can be done in spot markets or by bilateral contracts involving customers and suppliers. This paper is devoted to bilateral contracting, which is modeled as a negotiation process involving an iterative exchange of offers and counter-offers. This article focuses on local citizen energy communities. Specifically, it presents team and single-agent negotiation models, where each member has its sets of strategies and tactics and also its decision model. Community agents are equipped with intra-team strategies and decision protocols. To evaluate the benefits of CECs, models of both coalition formation and management have been adapted. This paper also describes a case study on forward bilateral contracts, involving a retailer agent and three different types of citizen energy communities. The results demonstrate the benefits of CECs during the negotiation of private bilateral contracts of electricity. Furthermore, they also demonstrate that in the case of using a representative strategy, the selection of the mediator may be critical for achieving a good deal.
- eMaPriCe - Estudo de Matérias-Primas Críticas e estratégicas e economia circular em PortugalPublication . Simoes, Sofia; Sousa Rocha, Cristina; Alexandre, Jorge; Catarino, Justina; Ferreira, Cristina; Oliveira, Paula; Amorim, Filipa; Niza, Samuel; Nogueira, CarlosRESUMO: O eMaPriCe tem por objetivo identificar oportunidades de implementação de estratégias de Economia Circular (EC), a fim de evitar que as Matérias-Primas Críticas (MPC) se transformem em resíduos, bem como opções da substituição destas por matérias-primas não críticas. Este estudo pretende também apresentar estratégias de recuperação das MPC presentes nos resíduos, dando assim resposta à Diretiva-Quadro Resíduos. O estudo focou-se nas 30 MPC na lista Europeia, bem como a cortiça natural, uma matéria-prima estratégica para Portugal, visto ser o seu maior produtor mundial. Estas 31 matérias-primas são designadas como MPC+. Foi feito uma identificação das aplicações na economia Portuguesa das MPC+ para os setores Têxteis e calçado; Cerâmica; Cortiça; Exploração mineira; Químicos e fertilizantes; Equipamentos elétricos e eletrónicos (EEE); Energias renováveis e Automóvel. Todas as MPC na lista europeia são utilizadas em Portugal para os setores considerados. O setor com maior diversidade na utilização de MPC+ é o setor dos EEE (26 MPC+), seguindo-se os setores químico e automóvel (24 MPC+ cada), e os têxteis (21 MPC+). As energias renováveis e cerâmica utilizam 14 e 13 MPC+, respetivamente, enquanto o calçado utiliza 11 MPC+. Por fim, tanto o setor da cortiça como da exploração mineira recorrem a apenas 2 MPC+ cada.
- Optimization of a biphasic biodesulfurization systemPublication . Silva, Tiago; Paixão, Susana M.; Roseiro, J. Carlos; Alves, LuísABSTRACT: Many of the new generation fuels, although more sustainable, share some of the problems inherent to fossil fuels. Depending on the biomass/material that originated them, they can present different contaminants that can lead to environmental problems. Sulfur is one of the most common and problematic contaminants in fuels. It is released into the atmosphere in the form of SOx, leading to the formation of acid rains, which cause drastic environmental and infrastructural problems, as well as several types of health issues. High sulfur concentrations in fuels also result in a loss of efficiency of motors and energy generation systems, mostly due to corrosion and catalyst poisoning. The current thermochemical desulfurization process, hydrodesulfurization (HDS), is energy demanding, pollutant and has low efficiency against more complex organosulfur molecules. This led researchers to look for new alternatives. Biodesulfurization (BDS), is, as the name implies, the biological removal of sulfur from fuels using microorganisms as living biocatalysts. If correctly employed this process could be more efficient and less pollutant, since microorganisms directly target the sulfur atoms, even those present in complex molecular structures, such as dibenzothiophene (DBT). Moreover, microbial activity occurs at much lower temperatures and pressures, without the need for metal catalysts, resulting in a lower energy demand. While BDS is a promising technology, it is still at a low development stage, mostly due to some bottlenecks, which have been hindering its large-scale application. Similarly, to other biotechnological processes, it presents lower reaction rates, when compared to HDS, since it depends on the use of living organisms as catalysts. Furthermore, it must be performed under conditions that allow the microorganisms to maintain biological activity, limiting the range of applications. These conditions vary greatly depending on the microorganism selected, and their optimization can significantly increase the biodesulfurization activity of a biocatalyst.
- A fast and effective analytical method to quantify the emulsifying activity: design and validationPublication . Alves, Luís; Tavares, João; Silva, Tiago; Paixão, Susana M.ABSTRACT: Biosurfactants (BS) and bioemulsifiers (BE) are amphiphilic molecules that are produced by a wide range of microorganisms. According to Willumsen and Karlson, BS/BE are both surface active biomolecules, but while the surfactants play the role of surface tension reduction, emulsifiers are involved in formation and stabilization of emulsions. However, some biomolecules possess both surfactant and emulsifying properties, which contributes to their unique features, including high biodegradability, low toxicity, effectiveness at extremes of temperature, pH and salinity, and special biological activities (e.g., antimicrobial, antiviral, anticancer, etc). These attributes make them an alternative to their chemical counterparts and allows them to have key roles in several fields. In fact, the chemical composition of BS and BE is different, and this may contribute to their specific roles in nature and biotechnological applications; however, both BS/BE have recognized emulsifying properties, which are the focus of this study. The idea of quantifying the emulsifying activity rather than quantifying the emulsifiers and/or surfactants themselves has been studied before. The concept that stands out is the emulsification index (E24: % emulsification after 24 h) proposed by Cooper and Goldenberg [4], which is still applied, and some of its adaptations such as the one proposed by Trebbau de Acevedo and McInerney. These authors have defined one unit of emulsifying activity as the amount of emulsifier that results in an emulsification (E24) of 20%. Although theoretically simple, these approaches require considerable sample volume, have a long wait (24 h) and are lengthy. Moreover, they can be subjective, since two substances might induce complete emulsion at 24 h, with one resulting in a much denser emulsion. This may indicate more BS/BE activity; however, it is not easily comparable, or demonstratable. Furthermore, due to nature of emulsions and the factors that influence them, small differences in test conditions, such as shape or size of the tubes, or nature of the hydrophobic layer, can generate drastic differences, which hinders reproducibility between authors.
- Effect of brewery effluent inhibitors on Rhodotorula toruloides NCYC 921 cells grown in pure and mixed cultures at pH 4 and 6Publication . Dias, Carla; Santos, J. A. L.; Reis, Alberto; Silva, Teresa Lopes daABSTRACT: The presence of inhibitor compounds in the culture medium can cause severe effects on the microorganisms cells. Brewery wastewaters present organic acids (acetic, propionic and butyric acids) which can severely affect yeast cells metabolism, when grown in pure cultures, although in mixed cultures they are able to develop. To understand the physiological changes on Rhodotorula toruloides (formerly Rhodosporidium toruloides) cells when fermenting in the presence of the organic acids present in brewery wastewater, pure and mixed cultures with the microalga Tetradesmus obliquus were performed in a synthetic medium containing the same organic acids concentrations that are present in brewery wastewater at pH 4 and 6. It was concluded that, at pH 4, the organic acids effects in the yeast cells were much more toxic than at pH 6. Moreover, mixed cultures can be an advantage over heterotrophic pure cultures as the microalga is able to contribute for the consumption of potential inhibitors for the yeast.
- Sustainable value methodology to compare the performance of conversion technologies for the production of electricity and heat, energy vectors and biofuels from waste biomassPublication . Moura, Patrícia; Henriques, José João M. Silva; Alexandre, Jorge; Oliveira, Ana Cristina; Abreu, Mariana; Gírio, Francisco; Catarino, JustinaABSTRACT: The Sustainable Value methodology was used to compare and rank eight combinations of waste biomass types and conversion technologies on a common assessment basis to produce energy, energy vectors and advanced biofuels. The studied combinations included agricultural and agro-industrial residues, slurries and effluents, pulp and paper mill sludge, piggery effluents and organic fractions of municipal solid waste, to produce biodiesel by (trans)esterification, biogas by anaerobic digestion, ethanol by fermentation, hydrogen by dark fermentation, electricity and heat by combustion, biogas and synthesis gas by gasification, and bio-oils by pyrolysis or hydrothermal liquefaction. The numerator “Functional Performance” of the Sustainable Value indicator was estimated according to 14 criteria of process technology, material and energy inputs and outputs, and acceptance by the stakeholders. The performance of the technologies was classified based on the values of relative importance (φ) and level of satisfaction (S) attributed to each criterion. The gasification of residues from the olive-oil industry reached the highest “Functional Performance”, followed by anaerobic digestion of chestnut processing residues and pig-rearing effluents. The Sustainable Value denominator “Costs” depended mainly on the degree of maturity of the technologies, which penalised pyrolysis, hydrothermal liquefaction and dark fermentation. The final ranking of the Sustainable Value indicator was gasification> combustion> anaerobic digestion> (trans)esterification> pyrolysis and fermentation to ethanol> hydrothermal liquefaction> dark fermentation, respectively for the most adequate waste biomass types under study. Thermochemical conversions were mainly impacted by process and input criteria, while output and social acceptance criteria were more decisive for the biochemical conversions.
- Metal hydride-based hydrogen production and storage system for stationary applications powered by renewable sourcesPublication . Rangel, C. M.; Fernandes, Vitor; Gano, AntónioABSTRACT: In this work, a compact and low-cost electrochemical laboratory prototype for the storage and production of hydrogen, based on metallic hydrides, with high reversibility in the charge/discharge process is demonstrated, using electricity either from the grid or by direct coupling to renewable energies as power source. The reactor is a 316 L stainless steel vessel with a capacity up to 15 bar internal pressure. It includes working electrodes of alloy LaNi4.3Co0.4Al0.3 and counter-electrodes of Ni foam in an electrolyte solution of 35% KOH. The reactor uses unicellular/multicellular configurations, so that the overall capacity of the system can be extended by increasing the number of working electrodes, resulting in a highly modular system. Results show excellent linearity, reversibility, and stability under cycling at room temperature and pressure, demonstrated either when powered by the grid or by off-grid renewable energy. Furthermore, criteria were established for the quantification of the state of full charge and full discharge. The system was integrated with a custom electronic system, developed inhouse for monitoring and control the reactor and to optimize the performance and energy efficiency of the hydrogen storage and discharge processes.
- A novel microbial biosurfactant/bioemulsifier: production and characterizationPublication . Silva, Tiago; Paixão, Susana M.; Tavares, João; Alves, LuísABSTRACT: Currently there is an immediate need for new and more sustainable production methods in most industries. The detergent industry, frequently associated with negative environmental impacts, is also in need of new alternatives, such as biosurfactants/bioemulsifiers (BS/BE). These are naturally synthetized compounds, classified as amphiphilic, for having both hydrophobic and hydrophilic properties. Their application results in a reduction of the surface tension between two immiscible phases, facilitating the mixture of different substances such as water and oil, or water and air (Tavares et al., 2021). BS/BE present several advantages over conventional detergents, they have lower toxicity and greater biodegradability, resulting in lower negative impacts to both consumers and ecosystems. Furthermore, these compounds present antibiotic, antiviral and antioxidant properties. They can be used in a broad range of pH, temperature and salinity and are effective at small concentrations. This makes them interesting for many other industries, such as food, cosmetics, pharmaceutical and chemical. BS/BE are commonly produced by microorganisms found in particular environments such as oil wells, hydrocarbon contaminated soils and solid waste lixiviates. These compounds facilitate the access to hydrophobic nutrient sources abundant in these environments, while also increasing the resistance of the microorganisms to such toxic environments. Gordonia alkanivorans strain 1B, is a bacterium with significant biotechnological potential, which was isolated from oil contaminated soils (Alves et al., 2005). It is mostly known for its biodesulfurizing properties, carotenoid production and broad catabolic range (Silva et al., 2016). The present work focuses on the potential of this strain to produce BS/BE compounds, initial purification and characterization.