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- Microalgae in a global world: New solutions for old problems?Publication . Vieira De Mendonça, Henrique; Assemany, Paula; Abreu, Mariana; De Aguiar Do Couto, Eduardo; Martins Maciel, Alyne; Duarte, Renata Lopes; Santos, Marcela Granato Barbosa dosABSTRACT: The human population blast has brought several problems related with the overconsumption of a wide range of feedstocks and natural resources conducting to their risk of depletion. The consumption of fossil fuels is an example, with increasing levels of exploitation and negative impacts caused by their use. Anthropogenic activities have triggered the over accumulation of many hazardous substances and wastes which are regarded to be detrimental to life in the Earth and to the various planet ecosystems. There is an urgent need to restore natural resources and unwanted residues and wastes to levels prior the demographic explosion. Microalgal biotechnology appears to be pivotal to achieve this goal in a near future to come. This review presents the current resource problems affecting the Earth and how microalgae are expected to be an important part of the solution, discussing how the production of renewable energy from microalgae can help in an integrated way to mitigate different environmental problems. Microalgae are able to convert wastewaters, CO2 and organic residues in marketable biomass for different uses, including biofuels, converting waste in value. An inventory of current microalgal-based biorefineries in operation as well as a directory of companies, products and applications are also presented.
- Enhancing microalgae biomass production: Exploring improved scraping frequency in a hybrid cultivation systemPublication . Silva, Thiago; Pereira, Alexia Saleme Aona de Paula; Ferreira, Jessica; Lorentz, Juliana F.; de Assis, Marilia Luise; Assemany, Paula; Reis, Alberto; Calijuri, Maria LuciaABSTRACT: Recently, hybrid systems, such as those incorporating high-rate algal ponds (HRAPs) and biofilm reactors (BRs), have shown promise in treating domestic wastewater while cultivating microalgae. In this context, the objective of the present study was to determine an improved scraping frequency to maximize microalgae biomass productivity in a mix of industrial (fruit-based juice production) and domestic wastewater. The mix was set to balance the carbon/nitrogen ratio. The scraping strategy involved maintaining 1 cm wide stripes to retain an inoculum in the reactor. Three scraping frequencies (2, 4, and 6 days) were evaluated. The findings indicate that a scraping frequency of each 2 days provided the highest biomass productivity (18.75 g total volatile solids m(- 2) d(-1)). The species' behavior varied with frequency: Chlorella vulgaris was abundant at 6-day intervals, whereas Tetradesmus obliquus favored shorter intervals. Biomass from more frequent scraping demonstrated a higher lipid content (15.45%). Extrapolymeric substance production was also highest at the 2-day frequency. Concerning wastewater treatment, the system removed 93% of dissolved organic carbon and similar to 100% of ammoniacal nitrogen. Combining industrial and domestic wastewater sources to balance the carbon/nitrogen ratio enhanced treatment efficiency and biomass yield. This study highlights the potential of adjusting scraping frequencies in hybrid systems for improved wastewater treatment and microalgae production.
- Energetic valorization of algal biomass in a hybrid anaerobic reactorPublication . Assemany, Paula; Calijuri, Maria Lucia; Silva, Teresa Lopes da; Reis, Alberto; Marques, Isabel PaulaABSTRACT: This study evaluated the operation of a hybrid anaerobic reactor fed with algal biomass cultivated in effluent from the brewery industry. Three stages of operation were distinguished during the 72 days of semi-continuous functioning of the reactor: Stage 1 (S1), in which algal biomass was used as substrate; Stage 2 (S2), in which 10% (v/v) of the algal biomass was substituted by olive mill wastewater (OMW); and Stage 3 (S3), in which algal biomass was heat pre-treated. During Sl, a loss of solids was observed, with an increment of organic matter in the outlet. The substitution of 10% of the volume of algal biomass by OMW tripled the methane productivity obtained in the previous stage by digestion of pure algal biomass. Heat pre-treatment was not efficient in rupturing the cell wall, and consequently did not have any effect on the increase in biogas production. The complementarity of substrates in the assessed conditions led to better results than the pre-treatment of the algal biomass.
- 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.
- 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.