Repositório do LNEG
National Laboratory of Energy and Geology Scientific Repository
Welcome to LNEG’s Scientific Repository
The LNEG’s Scientific Repository intends to preserve, disseminate and give access to LNEG's scientific production in digital format.
The objectives of the Repository are: to increase the visibility and impact of the research carried out at LNEG, to improve internal and external communication and to preserve the institution's intellectual memory.
Recent Submissions
Heat Flow Density Estimations in the Portuguese Northern Hercynian Massif using Silica Geothermometry
Publication . Correia, Antonio; Ramalho, Elsa
ABSTRACT: Surface heat flow density (HFD) estimates in the Portuguese northern Hercynian Massif are difficult to obtain using the usual Fourier method. As a matter of fact, this zone is mostly composed by granitoid and metamorphic rocks, and most wells drilled there are too shallow for reliable HFD calculations; furthermore, HFD estimates are scarce and their geographical distribution is still very irregular. All these conditions imply that a HFD map for this region must be obtained using alternative methods, such as the silica geothermometry method. Under certain conditions, the use of silica geothermometers to estimate HFD in mineral waters has proved to be an effective way to understand and establish the thermal regime in areas with scarce conventional HFD determinations. Because temperatures obtained with silica geothermometry are related to deep thermal conditions in the crust and to water-rock equilibrium, a regional HFD analysis may be carried out using those temperatures. The silica geothermometer, developed by Truesdell in 1976 (Truesdell, 1976), give good results for low SiO2 concentrations, which is the case for the Portuguese northern Hercynian Massif, and is applied to more than 30 samples of mineral water occurrences reported for the zone. This number of samples, even though small, is considerably higher and more evenly distributed than conventional HFD estimates for the same area. Application of silica geothermometry to northern Hercynian Massif waters shows a discrete reservoir temperature zoning, ranging from about 45 ºC, in its southwest limit, to more than 120 ºC, towards its northeast limit. Using temperatures obtained by silica geothermometry and heat flow density values calculated through the conventional method in an area of 1º x 1º in the study zone, an empirical linear relationship between HFD and temperatures obtained by silica geothermometry is obtained and used to construct a HFD map for the Portuguese northern Hercynian Massif. The resulting HFD map is compared with the general geological and structural framework, and an attempt to a geothermal characterisation of the Portuguese northern Hercynian Massif is made.
Assessment of piggery wastewater treatment in vertical flow constructed wetlands: role of plants and aeration
Publication . de Oliveira Corrêa, Diego; Ferreira, Alice; Ribeiro, Belina; Gogoi, Jayanta; Karan, N.; Nalwad, A.; Ganguly, A.; Mutnuri, S.; Gouveia, Luisa
ABSTRACT: Piggery wastewater (PWW), rich in pollutants, poses significant environmental risks if not properly treated. Natural treatment processes, such as constructed wetlands (combined action of plants, substrates, and microbes) and microalgae cultivation, offer sustainable and low-cost alternatives for managing these effluents while enabling resource recovery. This study represents an initial step toward optimizing key operational conditions, such as aeration (passive and active), vegetation presence, and the use of single or sequential Vertical Flow Constructed Wetlands (VFCWs), for the treatment of piggery wastewater, using different experimental setups, at a laboratory scale. Indoor experiments were conducted over an 8-week period to optimize operational conditions for the treatment of PWW. The VFCWs, arranged in two stages and operated in series through gravity flow, were fed daily and monitored weekly. The best removal rates of total Kjeldahl nitrogen (42.9 %), ammoniacal nitrogen (50.3 %), and chemical oxygen demand (20.5 %), were observed in the second stage of VFCW without aeration and with plant. Nitrate and phosphorus levels increased during the experiment, likely due to microbial activity within the substrate and plant root zones. The final goal is to treat the piggery wastewater from a rural farm in India, produce electricity (by a Microbial Fuel Cell), to generate an effluent suitable for microalgae cultivation, with the produced biomass intended for use either as a biostimulant to enhance cereal crops included in pig diets or as a direct nutritional supplement in pig feed.
Extraction and assessment of the colouring capacity of Arthrospira platensis-derived pigments
Publication . Villaro-Cos, Silvia; Gouveia, Luisa; Vladic, Jelena; Sanchez-Zurano, Ana; Martínez-García, Irene; Lafarga, Tomás
ABSTRACT: This study presents a zero-waste biorefinery approach for the sequential extraction of phycocyanin and chlorophyll from Arthrospira platensis, followed by the valorisation of the remaining biomass as a plant biostimulant. Natural deep eutectic solvents were screened for phycocyanin recovery, with the mixture proline:glycerol:sorbitol:water (1:1:1:13 molar ratio) showing the highest potential (1.15 g⋅100 g-1; p < 0.05). An initial ultrasound-assisted cell wall disruption step significantly enhanced phycocyanin yield by 400–450 % relative to the untreated control (p < 0.05). A response surface methodology optimised extraction achieved a recovery yield of 8.26 g⋅100 g-1 at 39.7 °C and 127.9 min. The phycocyanin-rich extract was used to mimic the blue colour of commercial blue gin, with a minimal colour difference (ΔE) of 4.53. Subsequent chlorophyll extraction from the phycocyanin leftovers yielded an extract that successfully coloured a commercial green alcohol-free apple liquor (ΔE = 3.93) and green gin (ΔE = 1.65). Finally, the residual biomass demonstrated a significant biostimulant capacity, increasing the germination index of various seeds by 80–150 % compared to water (p < 0.05). This work highlights the potential of A. platensis as a sustainable source for natural colourants and agricultural inputs.
Pretreatment Tunes scCO2 Extract Composition and Bioactivity in Three Microalgae: Chemometric and Molecular Docking Insights
Publication . Vladic, Jelena; Radman, Sanja; Besu, Irina; Stanojkovic, Tatjana; Zloh, Mire; Jerkovic, Igor; Karadžić Banjac, Milica; Ivkovic, Milena; Pereira, Hugo; Gouveia, Luisa
ABSTRACT: This study explores the impact of enzymatic (ENZ), microwave (MW), and ultrasound (US) pretreatments on supercritical CO2 (scCO2) extraction efficiency, chemical composition, and cytotoxic activity of Tetraselmis sp., Tetradesmus obliquus, and Chlorococcum sp. Pretreatments significantly enhanced extraction yields, with ENZ being most effective for Tetraselmis and Chlorococcum, and MW for T. obliquus. UPLC-HRMS profiling revealed species- and pretreatment-specific shifts: ENZ and US improved pigment recovery in Tetraselmis, while MW enriched carotenoids and chlorophyll derivatives. In Chlorococcum, MW boosted pigment diversity, whereas ENZ and US favored fatty acid derivatives in the extracts. Multivariate analysis confirmed significant compositional changes, particularly after ENZ and MW pretreatments. Tetraselmis extracts, especially those pretreated with MW, exhibited the strongest cytotoxic activity and highest selectivity indices against HeLa and MDA-MB-453 cancer cell lines. Correlation analysis identified compounds such as 2,3-dihydroxypropyl stearate, fucoxanthin, and (3 beta)-3-hydroxystigmast-5-en-7-one as strongly linked to cytotoxicity. Molecular docking further showed that abundant compounds in Tetraselmis extracts have high predicted affinities for cancer-related targets (e.g., BCL2, EGFR, PDK1). The results suggest that cytotoxic effects arise from both specific bioactive compounds and their synergistic interactions. These findings show that pretreatments can purposefully tune scCO2 extracts and provide a data-driven basis for designing more sustainable microalgal extraction workflows.
Phenological Development, Productivity, and Oil Profiles of Different Safflower Cultivars for Biofuel Production
Publication . Silva, Raimunda Adlany Dias; Gouveia, Luisa; Rocha, Thomaz Gabriel Barros; Gondim, Amanda Duarte; Lichston, Juliana Espada; Santos, Nataly Albuquerque
ABSTRACT: The production of oilseed biomass to meet the demand of the energy sector is constrained by several factors, including regional soil and climate conditions, phenological and production issues, such as yield and oil profile, and the compatibility of these factors with the requirements of the energy sector. Safflower is a small oilseed, and its brief phenological cycle and high productivity, concentration, and oil profile distinguish it as a notable candidate for research on energy applications. The objective of this study was to analyze the germination, seed vigor, yield, and oil profile parameters of safflower cultivars (IMAmt 1470, IMAmt 894, and IMAmt S525) with a view to determining their potential as biomass for the biofuel production chain, especially biodiesel and renewable aviation hydrocarbons. Safflower cultivars displayed high germination rates and germination vigor after 12 months of storage. They also met the production standards of 6797.7 kg ha-1 in 2021. The cultivar IMAmt-S525 exhibited a high oil content of 35%. The oil compositions of the safflower cultivars included in this study were found to be 9.7% palmitic acid (IMAmt1470), 71.82% linoleic acid (IMAmt 894), and 41% oleic acid (IMAmt 894 harvest 2022). It is recommended that the following cultivars be selected for production: IMAmt 894, IMAmt-S525, and IMAmt 1470, taking into consideration the physiological, production, and oil composition parameters. Since all three cultivars have high standards of physiological quality, productivity, and oil yield, they have the potential to be used as biomass to diversify oilseed matrices for biofuels.