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Optimizing Chlorella vulgaris production and exploring its impact on germination through microalga-N2-fixing bacteria consortia
Publication . Sanchez-Zurano, Ana; Vilaro-Cos, Silvia; Figueiredo, Daniel; Melkonyan, Lusine; Ferreira, Alice; Acien Fernandez, F. Gabriel; Lafarga, Tomás; Gouveia, Luisa
ABSTRACT: Microalgal biomass is increasingly valued in industrial and agricultural sectors due to its bioactive compounds. However, large-scale production remains costly, mainly due to nitrogen fertilizer expenses. A promising sustainable alternative is co-cultivation with N2-fixing bacteria, capable of supplying biologically available nitrogen. In this study, Chlorella vulgaris was grown in synthetic medium with and without nitrogen, as well as in co-culture with three different N2-fixing bacteria in nitrogen-free medium. Microalgal growth was assessed by dry weight, Fv/Fm ratio, and flow cytometry, which also allowed evaluation of population dynamics and cell viability. Biomass composition (proteins, carbohydrates, lipids, chlorophyll, and carotenoids) was analyzed under all conditions. Co-cultures in nitrogen-free medium showed comparable biomass productivity to nitrogen-supplemented controls, although Fv/Fm values indicated physiological stress in some cases. Moreover, the agricultural potential of the resulting biomass and supernatants was evaluated through germination bioassays using lettuce seeds. All cultures tested at 0.2 g & sdot;L-1 significantly improved the germination index. Also, applying the culture supernatant (biomass removed) also yielded positive effects, with GI increases exceeding 40 %. These results suggest that co-cultivation with N2-fixing bacteria can support efficient microalgal production while generating biomass and supernatants with biostimulant potential, contributing to sustainable agriculture and circular bioeconomy strategies.
Determination of reflectance of interest from limited state-of-the-art solar reflector field soiling measurements
Publication . Wette, Johannes; Sutter, Florian; Cunha Diamantino, Teresa; Montecchi, Marco; Bern, Gregor; Fernández-García, Aránzazu
ABSTRACT: In concentrated solar thermal technologies, plant operators usually monitor the soiling of their solar field with handheld reflectometers. These measurements can be used for yield calculations and to adapt cleaning strategies: if the reflectometer reading falls below an empirically established threshold, the solar field should be cleaned. There are several commercial reflectometers available for this purpose, but all of them measure at different combinations of wavelength, acceptance angle or incidence angle. It is the purpose of this study to bring the readings from all main commercial reflectometers to the same representative value, enabling their comparison with one another and the translation of these readings into a meaningful reflectance parameter. Thus, different handheld reflectometers are correlated with a laboratory reflectometer, capable of measuring in the whole solar spectral region, covering a wide range of incidence and acceptance angles. The most significant parameter is the near-specular solar-weighted reflectance, measured at the typical incidence and acceptance angles for a given plant, as it is the most precise parameter to describe the reflected energy from the solar field. The correlations for all included reflectometers, show highly linear correlations over a wide range of soiling levels with low deviations. Consequently, the correlations presented herein enable the plant operators at the studied site to compute the near-specular solar-weighted reflectance from their reflectometer readings. and, with that, increase the significance of the measurements without collecting any additional data. The work also establishes a detailed procedure to derive this type of correlations at any site of interest.
Como o trabalho do LNEG apoia a concretização do PNEC: Plano Nacional de Energia e Clima - Conheça 10 dos trabalhos do LNEG que contribuem para a concretização do PNEC
Publication . Simoes, Sofia; Simões, Teresa; Barbosa, Juliana Pacheco; Rodrigues, Carlos; Azevedo, Pedro; Cardoso, João; Facão, Jorge; Costa, Paula Silva; Justino, Paulo Alexandre; Gírio, Francisco; Reis, Alberto; Passarinho, Paula; Duarte, Luís; Moura, Patrícia; Abreu, Mariana; Estanqueiro, Ana; Couto, António; Oliveira, Paula; Quental, Lídia; Patinha, Pedro; Catarino, Justina; Picado, Ana; Ramalho, Elsa; de Oliveira, Daniel Pipa Soares; Filipe, Augusto; Albardeiro, Luís; Santos, Sara; Gonçalves, Pedro
Unprecedented U-Pb-Th SHRIMP and Lu-Hf isotopic data in zircon from Tandilia basement rocks, Argentina: new insights into Palaeoproterozoic and Neoproterozoic crustal reworking of the Rio de la Plata craton
Publication . Angeletti, Melisa; Chichorro, Martim Afonso; Castro, Antonio; Frisicale, María Cristina; Solá, A. Rita; Dimieri, Luis Vicente; Martinez, Juan Cruz
ABSTRACT: We present new geochronological zircon data from the Siempre Amigos Hill (SAH), a small but representative portion of Tandilia Terrane within the R & iacute;o de la Plata Craton (RPC). U-Pb-Th SHRIMP data indicate a heterogeneous Palaeoproterozoic (Rhyacian) crust. A garnet-bearing granite (2165 +/- 16 Ma) hosts felsic (2108 +/- 13.6 Ma) to intermediate gneiss protolith (2104 +/- 8 Ma), andesite with a sanukitoid signature (2094 +/- 47 Ma) and granulites or charnockites. Additionally, calc-alkaline granitoids (2092 +/- 13 Ma) intruded, as a result of differentiation from an igneous mafic sanukitoid source. Localised low-temperature shear zones affected the sequence. Lu-Hf isotopic data for the post-orogenic stage (< 2.1 Ga) complement previous results, showing progressive negative epsilon Hf-(t) values. These isotopes suggest post-orogenic transtension. New Neoproterozoic ages (652 +/- 37 Ma, 618.4 +/- 11.2 Ma and 686 +/- 60 Ma) from granites, with low-to-very low zircon Th/U ratios, are presented as evidence of U-Th-Pb systems overprinting by Neoproterozoic (Cryogenian) thermal-hydrothermal events. Those Neoproterozoic ages are, within analytical uncertainty, equivalent to the 656 +/- 19 Ma metamorphic age obtained for the Palaeoproterozoic granulite. These new Neoproterozoic ages, suggests a thermal perturbation linked either to the collision of the Nico Perez Terrane against the passive margin of RPC, or the Neoproterozoic evolution of the Ventania System basement during the Brasiliano/ Pan-African orogeny.
Improving bio-oil fractions through fractional condensation of pyrolysis vapors from Eucalyptus globulus biomass residues in a prototype auger reactor
Publication . Vilas-Boas, A.C.M.; Tarelho, L.; Marques, C.C.; Moura, J.M.O.; Santos, M.C.; Paradela, Filipe; Nunes, M.I.; Silvestre, A.J.D.
ABSTRACT: Bio-oil produced from the pyrolysis of lignocellulosic biomass has potential as a biofuel or chemical precursor. However, its valorization is hindered by its complex composition, high water concentration, and the presence of oxygenated compounds. Operational strategies are therefore required to improve its quality. This study evaluated the technical feasibility of fractional condensation as an alternative to conventional single-stage condensation of vapors produced from pyrolysis of residual Eucalyptus globulus biomass to collect bio-oil fractions with improved properties. The process was carried out using a prototype-scale auger reactor with continuous operation. The fractional condensation system comprised four sequential condensation stages operating at progressively lower temperatures: 140, 100, 80, and 0 degrees C. The collected bio-oil fractions were analyzed in terms of product yields, water separation efficiency, elemental composition, heating value, and the presence of volatile and semi-volatile compounds. The results demonstrated that fractional condensation achieved total bio-oil yields comparable to those obtained with the single-stage condensation system, while enabling the recovery of bio-oil fractions with lower water concentration, higher carbon concentration and increased heating value. Notably, the first condensation stage collected heavy fractions with water concentration between 3 % and 6 %wt., oxygen concentration between 17 % and 21 %wt., and carbon concentration between 69 % and 72 %wt., resulting in O/C molar ratios between 0.17 and 0.22, values close to those of biodiesel. These fractions exhibited lower heating values of up to 31 MJ/kg, surpassing those of conventional liquid biofuels such as biomethanol and bioethanol. These findings highlight the potential of fractional condensation of pyrolysis vapors from residual biomass from Eucalyptus globulus as an effective strategy to produce bio-oil with properties more suitable for direct energy use or as an intermediate feedstock for biofuels synthesis. Further research is recommended to optimize the condensation stages and assess the long-term stability of recovered fractions.