Browsing by Author "Mata, T.M."
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- Application of domestic greywater for irrigating agricultural products: A brief studyPublication . Gorgich, M.; Mata, T.M.; Martins, A; Caetano, Nídia; Formigo, N.The decline in annual rainfall, coupled with the growing demand for water in agricultural fields, triggered a new crisis in today’s world. Thus, the focus is on finding solutions to new water resources. Taking a look at the normal daily life, most of the households’ effluents can be ranked into a less-polluted category, called greywater. Excluding human dejects, greywater comprises the outflow from washing machines, dishwashers and bathtubs. It is considered an effluent with a more economic treatment, because it contains less microbial pollution. Hence, this work revises the effects of greywater irrigation on the quality of crops, and provides a comprehensive study of the effects of greywater on the quality of soil. Furthermore, a comprehensive discussion is carried out to evaluate the energy consumption of facilities for both greywater and wastewater treatment to provide water used in irrigation. It also addresses current methodologies for treating greywater and evaluates the effects of crops irrigation with treated and untreated greywater, indicating the type of treatment chosen depending on the type of crop to be irrigated.
- 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.
- 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.
- Economic analysis of microalgae biodiesel production in a small-scale facilityPublication . Branco-Vieira, M.; Mata, T.M.; Martins, A.A.; Freitas, M.A.V.; Caetano, NídiaIndustrial production and commercialization of biodiesel from microalgae have become a good alternative to conventional feedstock. Microalgae show high growth rate and carbon sequestration and can be easily cultivate in fresh and/or marine water, using non-arable soil. This study aims to analyze the technical and economic feasibility of biodiesel production from Phaeodactylum tricornutum, using an algae biomass production scaled-up scenario, considering local reality prices and available technologies. The model assumes 80,000 m3 of microalgae cultivation, in a set of bubble column photobioreactors installed on 15.247 ha of land, reaching a total of 1,811 tons of microalgae biomass and 171,705 L of biodiesel per year. The production cost estimated for microalgae biomass is 2.01 € kg−1 and for biodiesel is 0.33 € L−1. The ROI calculated for the project is 10% with a 10 years’ payback time and an EBITDA of 588,139 € year−1. Despite the project’s viability in the medium term, the cost of producing microalgae biodiesel remains high when compared to fossil fuels. Thus, unless greater technological maturity is achieved to make the process more economical, it will not be viable in the short term.
- 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.
- Influence of cultivation conditions on the bioenergy potential and bio-compounds of Chlorella vulgarisPublication . Caetano, Nídia; Melo, A.R.; Gorgich, M.; Branco-Vieira, M.; Martins, A.A.; Mata, T.M.This study aims to evaluate the influence of cultivation conditions on the bioenergy and high value biocompounds contents of Chlorella vulgaris. Results show that the use of nitrate rich media, from 170.7 mg/L, favors a faster biomass growth, reaching values above 800 mg/L biomass. In addition, it favors higher pigments concentrations with more emphasis for the cultures with a nitrate concentration of 569 mg/L, where chlorophyll-a and carotenoids reached maximum concentrations of 6 and 2 mg/L, respectively. As regards the lipid content, nitrate deprivation (<28.4 mg/L) favors the accumulation of lipid content by microalgae (around 42%). The use of media with lower iron concentrations (0.5 mg/L) was favorable for obtaining biomass with higher concentrations of chlorophyll-a, at an initial stage, with values varying from 0.2 to 0.6 mg/L. In the tests carried out under mixotrophic conditions (addition of glucose), it was observed that contamination occurred in all the cultures, possibly due to the high concentration of carbon source that had values between 0.5 and 1.5 g/L of glucose, and consequently, growth decreased.
- LCA: A tool to develop sustainable microalgal biorefineriesPublication . Caetano, N.S.; Corrêa, P.S.; Morais Júnior, W. G.; Mata, T.M.; Martins, A.A.A.; Branco Vieira, M.Microalgae biorefineries, similar to oil refineries, are planned to exploit and maximize the value of microalgae biomass, producing as many products as possible. The biorefinery flowsheet can take different configurations, depending on the target products and the technologies to be applied. Due to the diversity of microalgae composition and strain phenotypic plasticity, some constraints can be faced for choosing the ideal candidate species. However, there are several alternatives to explore the potentiality of a strain that can make the biorefinery economically viable, environmentally friendly, and socially acceptable. Life cycle assessment (LCA) is a tool that allows evaluating the environmental impacts of a product, process, or system, and should be used to assess the environmental performance of a planned biorefinery. When combined with life cycle costing (LCC) evaluation and social life cycle assessment (S-LCA), LCA allows to take informed decisions on the most adequate biorefinery to implement. Nevertheless, and although many of the processes used in microalgae-based biorefineries are common to those used in other well-established industries, the biorefinery is an emerging area where usually novel technologies are required, some of them applied only on a pilot or a laboratory scale, making the available data limited or highly sensitive to variations. This chapter discusses the application of LCA to biorefineries, the potential hurdles, and limitations.
- 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.
- Life cycle assessment of a vanadium flow batteryPublication . Gouveia, J.; Mendes, A.; Monteiro, R.; Mata, T.M.; Caetano, Nídia; Martins, A.A.Battery storage technologies have been showing great potential to address the vulnerability of renewable electricity generation systems. Among the various options, vanadium redox flow batteries are one of the most promising in the energy storage market. In this work, a life cycle assessment of a 5 kW vanadium redox flow battery is performed on a cradle-to-gate approach with focus on the vanadium electrolytes, since they determine the battery’s storage capacity and can be readjusted and reused indefinitely. The functional unit is 1 kWh stored by the battery. The initial results show that the environmental hotspots reside mainly in the structural and material components of the battery, evidencing the need for alternative or recycled materials, preferably produced locally. Since the quantity of electrolytes determine the amount of storable electricity, an analysis was conducted on the variation of the impacts with the increase of storage capacity. An alternative scenario with reused electrolytes was also performed. Results show that with the increase of storage capacity, the contribution of the electrolytes to the impacts decrease significantly by stored kWh. In the reused electrolytes scenario, impacts were reduced mainly for the Acidification and Mineral, fossil and renewable resource depletion categories.
- 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.