Browsing by Author "Reis, Alberto"
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- Algal biomass production and wastewater treatment in high rate algal ponds receiving disinfected effluentPublication . Santiago, Aníbal F.; Calijuri, Maria Lucia; Assemany, Paula; Calijuri, Maria do Carmo; Reis, AlbertoAlgal biomass production associated with wastewater is usually carried out in high rate algal ponds (HRAPs), which are concomitantly used in the treatment of such effluent. However, most types of wastewater have high levels of bacteria that can inhibit the growth of algal biomass by competing for space and nutrients. The objective of this study was to assess the influence of ultraviolet (UV) pre-disinfection on the performance of HRAPs used for wastewater treatment and algal biomass production. Two HRAPs were tested: one received effluent from an upflow anaerobic sludge blanket (UASB) reactor – HRAP – and the second received UASB effluent pre-disinfected by UV radiation – UVHRAP. Physical, chemical and microbiological parameters were monitored, as well as algal biomass productivity and daily pH and dissolved oxygen (DO) variation. The UVHRAP presented highest DO and pH values, as well as greater percentage of chlorophyll a in the biomass, which indicates greater algal biomass productivity. The average percentages of chlorophyll a found in the biomass obtained from the HRAP and the UVHRAP were 0.95±0.65% and 1.58±0.65%, respectively. However, total biomass productivity was greater in the HRAP (11.4 gVSS m-2 day-1) compared with the UVHRAP (9.3 gVSS m-2 day-1). Mean pH values were 7.7±0.7 in the HRAP and 8.1±1.0 in the UVHRAP, and mean values of DO percent saturation were 87±26% and 112±31% for the HRAP and the UVHRAP, respectively. Despite these differences, removal efficiencies of organic carbon, chemical oxygen demand, ammoniacal nitrogen and soluble phosphorus were statistically equal at the 5% significance level.
- Anaerobic digestion of pre-treated microalgae biomassPublication . Neves, André; Silva, Teresa Lopes da; Reis, Alberto; Ramalho, Luís; Eusebio, Ana; Marques, Isabel PaulaABSTRACT: Chlorella vulgaris microalgae biomass was cultivated in brewery secondary effluents and used as a recalcitrant effluent to be valorised energetically by anaerobic digestion process. All previous techniques applied for cellular disruption – autoclave, freeze/heating, ultrasound, microwave - provided either high absorption values and release of reducing sugars in the medium or membrane cells damage, compared to the untreated sample, indicating that the pre-treatment action was effective. The highest methane production was attained by the autoclave and untreated microalgae assays (samples with less permeabilized cells) while the lowest was provide by the microwaves biomasses pre-treatment: 163-178 mL versus 67 mL CH4. COD removal of 27-29 % and 16 % and TS removal of 28-32 % and 17 % were obtained, respectively. The corresponding methane yield achieved values of 0.04 and 0.030 L g-1 COD and 0.205-0.235 L g-1 TS related to concentrations determined in the influent.
- Anaerobic digestion of pre-treated microalgae biomass [Resumo]Publication . Neves, André; Silva, Teresa Lopes da; Reis, Alberto; Ramalho, Luís; Eusebio, Ana; Marques, Isabel Paula
- Applications and perspectives of multi-parameter flow cytometry to microbial biofuels production processesPublication . Silva, Teresa Lopes da; Roseiro, J. Carlos; Reis, AlbertoConventional microbiology methods used to monitor microbial biofuels production are based on off-line analyses. The analyses are, unfortunately, insufficient for bioprocess optimization. Real time process control strategies, such as flow cytometry (FC), can be used to monitor bioprocess development (at-line) by providing single cell information that improves process model formulation and validation. This paper reviews the current uses and potential applications of FC in biodiesel, bioethanol, biomethane, biohydrogen and fuel cell processes. By highlighting the inherent accuracy and robustness of the technique for a range of biofuel processing parameters, more robust monitoring and control may be implemented to enhance process efficiency.
- Benchmarking commercially available value-added fractions with potential for production via microalgae-based biorefineries: is it worth it?Publication . Ferreira, Flávio; Reis, Alberto; Ortigueira, Joana; Lopes, TiagoABSTRACT: The urgent need to mitigate climate change requires finding sustainable and efficient alternatives to fossil fuel-based materials. Biosequestration by microalgae has been suggested as a potential method for climate change mitigation due to its environmentally friendly nature and ability to produce high-value compounds. However, the large-scale application of microalgal biorefineries faces significant challenges, particularly in the harvest and processing stages, which are often costly and energy-intensive. This study aims to benchmark value-added fractions that can be produced via microalgae-based biorefineries against their commercially available counterparts. A systematic review was conducted using the Web of Science™ database to identify current commercial sources of proteins, lipids, polyunsaturated fatty acids and pigments, this study identified key sectors and applications for each fraction, as well as potential market competitors. The results highlight substantial cost differences across production systems, with traditional agricultural sources demonstrating lower CAPEX but greater environmental challenges. Meanwhile, microalgal systems, although associated with higher CAPEX, offer advantages such as reduced land and water dependency, potentially leading to long-term economic resilience and environmental sustainability. By pinpointing research trends, key sectors and optimization opportunities, this work offers valuable insights into the profitability and competitiveness of microalgal systems, providing a benchmark for future optimization efforts. The novelty of this research lies in its comprehensive comparison of microalgae-based and traditional production systems, establishing a clear benchmark for microalgal production and suggesting focus areas for enhancement.
- Biodiesel from heterotrophic and autotrophic microalgae: a sustainable production [Poster]Publication . Santos, Carla A.; Semião, Filipe; Barata, Carlos; Reis, Alberto
- Biodiesel from microalgae Chlorella protothecoides growing at autotrophic and heterotrophic metabolisms in a new symbiotic bioreactorPublication . Santos, Carla A.; Reis, AlbertoBiodiesel is an alternative energy to fossil fuels, and is produced from biomass, therefore provides lower CO2 emissions. Currently, biodiesel is produced from plant oils, animal fats and used oils. These sources are low-yield which is a limitation to the production of biodiesel in large quantities. On the contrary, microalgae present a very high yield and can be produced in large amounts. The bio-refinery of microalgae oil must have a strategy of taking advantage of all by-products to make the whole process economic feasible. The bio-refinery proposed on this work is based on a first step to produce microalgae in a symbiotic bioreactor. The symbiotic bioreactor consists of an association of a fermenter and a photobioreactor connected by the gas phase on closed circuit. Two sorts of microalgae biomass are obtained: the heterotrophic microalgae from the fermenter and the autotrophic microalgae from the VAP (vertical alveolar panel photobioreactor). The best strategy is to use the heterotrophic microalgae to extract the oil as it has a higher content in lipids, and, then to produce biodiesel; additionally carotenoids as lutein can be extracted along with lipids from the heterotrophic microalga as a High Value Product (HVP). On the other hand, the autotrophic microalgae go to a second step of carotenoids accumulation, named carotenogenesis, to produce a biomass rich in carotenoids, also known as HVP. Carotenoids can be extracted and the residue of microalga, join to the other residues of microalgae to be processed by anaerobic digestion. The heterotrophic microalgae residue after oil and lutein extraction can be submitted to anaerobic digestion to produce methane or hydrogen. The case of microalga Chlorella protothecoides was studied, because it can grow under the two metabolisms referred above, and the lipids obtained are suitable to produce biodiesel. The yields obtained are quite favourable to the symbiotic system, instead of the separated bioreactors. The carbon dioxide emissions can be reduced by the autotrophic growth of microalgae. The sustainability of the bio-refinery was ensured in order to achieve an economic feasible system.
- Biodiesel from wastewater: lipid production in high rate algal pond receiving disinfected effluentPublication . Assemany, Paula; Calijuri, Maria Lucia; De Aguiar Do Couto, Eduardo; Reis, AlbertoThe production of different species of microalgae in consortium with other micro-organisms from wastewaters may represent an alternative process, to reduce the costs, for obtaining biofuels. The aim of this study was to evaluate the influence of pre-ultraviolet disinfection (UV) in the production of lipids from biomass produced in high rate ponds. Two high rate algal ponds were evaluated: a pond that received domestic sewage without disinfection and the other receiving domestic sewage previously disinfected by UV radiation (uvHRAP). The UV disinfection did not lead to significant differences in fatty acid profile and total lipid productivities, although it increased algal biomass concentration and productivity as well as lipid content. Moreover, the overall biomass concentrations and productivities decreased with the UV disinfection, mostly as a consequence of a loss in bacterial load. We thus conclude that uvHRAP disinfection may represent a potential strategy to promote the cleaner and safer growth of algal biomass when cultivated in consortium with other microorganisms. Mainly regarding the use of wastewater as culture medium, together with a cheaper production of lipids for biodiesel, pre-disinfection may represent an advance since extraction costs could be significantly trimmed due to the increase in lipid content.
- Biofuel from wastewater-grown microalgae: A biorefinery approach using hydrothermal liquefaction and catalyst upgradingPublication . Silva, Thiago; de Aguiar do Couto, Eduardo; Assemany, Paula; Costa, Paula; Marques, Paula; Paradela, Filipe; Reis, Alberto; Calijuri, Maria LuciaABSTRACT: Third-generation biofuels from microalgae are becoming necessary for sustainable energy. In this context, this study explores the hydrothermal liquefaction (HTL) of microalgae biomass grown in wastewater, consisting of 30% Chlorella vulgaris, 69% Tetradesmus obliquus, and 1% cyanobacteria Limnothrix planctonica, and the subsequent upgrading of the produced bio-oil. The novelty of the work lies in integrating microalgae cultivation in wastewater with HTL in a biorefinery approach, enhanced using a catalyst to upgrade the bio-oil. Different temperatures (300, 325, and 350 degrees C) and reaction times (15, 30, and 45 min) were tested. The bio-oil upgrading occurred with a Cobalt-Molybdenum (CoMo) catalyst for 1 h at 375 degrees C. Post-HTL, although the hydrogen-to-carbon (H/C) ratio decreased from 1.70 to 1.38-1.60, the oxygen-to-carbon (O/C) ratio also decreased from 0.39 to 0.079-0.104, and the higher heating value increased from 20.6 to 36.4-38.3 MJ kg(-1). Palmitic acid was the main component in all bio-oil samples. The highest bio-oil yield was at 300 degrees C for 30 min (23.4%). Upgrading increased long-chain hydrocarbons like heptadecane (5%), indicating biofuel potential, though nitrogenous compounds such as hexadecanenitrile suggest a need for further hydrodenitrogenation. Aqueous phase, solid residues, and gas from HTL can be used for applications such as biomass cultivation, bio-hydrogen, valuable chemicals, and materials like carbon composites and cement additives, promoting a circular economy. The study underscores the potential of microalgae-derived bio-oil as sustainable biofuel, although further refinement is needed to meet current fuel standards.
- Biofuel recovery from microalgae biomass grown in dairy wastewater treated with activated sludge: the next step in sustainable productionPublication . Mendonca, Henrique Vieira de; Otenio, Marcelo Henrique; Marchão, Leonilde; Lomeu, Alice; Souza, Denise Salvador de; Reis, AlbertoABSTRACT: Microalgae biofuel could be the next step in avoiding the excessive use of fossil fuels and reducing negative impacts on the environment. In the present study, two species of microalgae (Scenedesmus obliquus and Chlorella vulgaris) were used for biomass production, grown in dairy wastewater treated by activated sludge systems. The photobioreactors were operated in batch and in continuous mode. The dry biomass produced was in the range of 2.30 to 3.10 g L-1. The highest volumetric yields for lipids and carbohydrates were 0.068 and 0.114 g L-1 day(-1). Maximum CO2 biofixation (750 mg L-1 day(-1)) was obtained in continuous mode. The maximum values for lipids (21%) and carbohydrates (39%) were recorded in the batch process with species Scenedesmus obliquus. In all of the experiments, the Linolenic acid concentration (C18:3) was greater than 12%, achieving satisfactory oxidative stability and good quality. Projected biofuel production could vary between 4,863,708 kg and 9,246,456 kg year(-1) if all the dairy wastewater produced in Brazil were used for this purpose. Two hectares would be needed to produce 24,99 x 10(9) L year(-1) of microalgae bioethanol, a far lower value than used in cultivating sugar cane. If all dairy wastewater generated annually in Brazil were used to produce microalgae biomass, it would be possible to obtain approximately 30,609 to 53,647 barrels of biodiesel per year. These data show that only by using dairy wastewater would biofuels be produced to replace 17% to 40% of the fossil fuels currently used in Brazil.