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Economic analysis of microalgae biodiesel production in a small-scale facility

Publication . Branco-Vieira, M.; Mata, T.M.; Martins, A.A.; Freitas, M.A.V.; Caetano, Nídia

Industrial 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.

2020Journal article

Open access

Flocculation of Arthrospira maxima for improved harvesting

Publication . 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.

2019Conference object

Open access

Sustainability evaluation of a Portuguese “terroir” wine

Publication . 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.

2019Conference object

Open access

Application of domestic greywater for irrigating agricultural products: A brief study

Publication . 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.

2020Journal article

Open access

Influence of cultivation conditions on the bioenergy potential and bio-compounds of Chlorella vulgaris

Publication . 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.

2020Journal article

Open access