From tiny microalgae to huge biorefineries

Microalgae are an emerging research field due to their high potential as a source of several biofuels in addition to the fact that they have a high-nutritional value and contain compounds that have health benefits. They are also highly used for water stream bioremediation and carbon dioxide mitigation. Therefore, the tiny microalgae could lead to a huge source of compounds and products, giving a good example of a real biorefinery approach. This work shows and presents examples of experimental microalgae-based biorefineries grown in an autotrophic mode at a laboratory scale

Nitratos nas águas de consumo no Distrito de Beja : da aplicação de um modelo regional integrado de avaliação ambiental ao estabelecimento de um sistema de vigilância epidemiológica

Apresenta-se uma perspectiva geral da problemática da presença de nitratos nas águas de consumo do Distrito de Beja e as linhas de acção para uma abordagem multidisciplinar e integrada do problema ambiental e de saúde pública, absolutamente necessária para resolução de uma situação preocupante nalguns concelhos do distrito. Com base num modelo regional de avaliação ambiental que permite identificar não só, as áreas mais sensíveis à poluição dos recursos hídricos pelos nitratos mas, igualmente, os prováveis sectores e factores mais relevantes envolvidos na problemática, propõe-se a criação de um Sistema de Vigilância Epidemiológica Ambiental. Deste modo, cruzando informação de cariz ambiental com dados da potencial população em risco e dos grupos mais vulneráveis envolvidos, nomeadamente quando ocorram situações de metahemoglobinémia em lactentes e grávidas ou potenciais efeitos cancerígenos em adultos, será possível desenvolver acções de prevenção do risco e de promoção da saúde das populações

Fermentative hydrogen production from microalgal biomass by a single strain of bacterium Enterobacter aerogenes: effect of operational conditions and fermentation kinetics

ABSTRACT: Biohydrogen production through dark fermentation is a promising technology for generating renewable energy, while using microalgal biomass as a third generation feedstock can further increase the sustainability of the process. In the present study, Scenedesmus obliquus was used as model microalga substrate for studying the impact of operational parameters in batch dark fermentation trials using a strain of Enterobacter aerogenes bacteria. (i) The initial gas-liquid ratio in the bioreactor (from 13 to 8.2) was tested, resulting in higher bioH(2) yields for ratios above 5. (ii) Different bacterial growth, inoculation procedures and fermentation media were tested in combined experiments. The best conditions were chosen by maximising bioH(2) yield and minimising production time and costs. (iii) The autoclave sterilization effect on sugar extraction and bioH(2) yield was tested for different microalga concentrations (2.5-50 g/L) with best results attained for 2.5 g/L (81.2% extraction yield, 40.9 mL H-2/g alga). For the best operational conditions, fermentation kinetics were monitored and adjusted to the Modified Gompertz model, with t(95) (time required for bioH(2) production to attain 95% of the maximum yield) below 4.5 h. The maximum hydrogen production was higher when using wet algal biomass enabling the energy Consuming biomass drying step to be skipped.info:eu-repo/semantics/publishedVersio

Production and storage of biohydrogen during sequential batch fermentation of Spirogyra hydrolyzate by Clostridium butyricum

The biological hydrogen production from Spirogyra sp. biomass was studied in a SBR (sequential batch reactor) equipped with a biogas collecting and storage system. Two acid hydrolysis pre-treatments (1N and 2N H2SO4) were applied to the Spirogyra biomass and the subsequent fermentation by Clostridium butyricum DSM 10702 was compared. The 1N and 2N hydrolyzates contained 37.2 and 40.8 g/L of total sugars, respectively, and small amounts of furfural and HMF (hydroxymethylfurfural). These compounds did not inhibit the hydrogen production from crude Spirogyra hydrolyzates. The fermentation was scaled up to a batch operated bioreactor coupled with a collecting system that enabled the subsequent characterization and storage of the biogas produced. The cumulative hydrogen production was similar for both 1N and 2N hydrolyzate, but the hydrogen production rates were 438 and 288 mL/L.h, respectively, suggesting that the 1N hydrolyzate was more suitable for sequential batch fermentation. The SBR with 1N hydrolyzate was operated continuously for 13.5 h in three consecutive batches and the overall hydrogen production rate and yield reached 324 mL/L.h and 2.59 mol/mol, respectively. This corresponds to a potential daily production of 10.4 L H2/L Spirogyra hydrolyzate, demonstrating the excellent capability of C. butyricum to produce hydrogen from microalgal biomass

Scenedesmus obliquus: biogas production from residues of biodiesel/bioethanol extraction processes [Resumo]

The aim of the present study was to evaluate the digestibility and the potential of biomethane production of Scenedesmus obliquus microalga, considering different biomass substrates

Nannochloropsis oceanica biomass enriched by electrocoagulation harvesting with promising agricultural applications

ABSTRACT: Electrocoagulation is a promising technology to harvest and concentrate microalgae while saving costs on secondary dewatering steps. However, the sacrificial electrodes release salts that impact the media and the harvested biomass. This study evaluated the effects of Fe, Zn, and Mg electrodes on Nannochloropsis oceanica harvesting and elementary composition of biomass and supernatants. Moreover, plant bioavailability of electrocoagulation minerals attached to biomass was assessed in the tomato plant model Solanum lycopersicum (cv. ‘Cherry’). Fe electrodes had better performance at lower power consumption and operation costs, followed by Zn and Mg. Electrocoagulation changes biomass and supernatant nutrient composition. Electrodes precipitated Mg and Ca from the nutrient media, enriching N. oceanica biomass, but increased Pb 2–4 times and depleted P in supernatants. Finally, Fe and Mg electrode metals in the biomass were proven bioavailable to S. lycopersicum seedlings, making electrocoagulation harvested biomass a promising bioresource to agricultural applications.info:eu-repo/semantics/publishedVersio

Third generation biohydrogen pProduction by Clostridium butyricum and adapted mixed cultures from Scenedesmus obliquus microalga biomass

Scenedesmus obliquus biomass was used as a feedstock for comparing the biological production of hydrogen by two different types of anaerobic cultures: a heat-treated mixed culture from a wastewater treatment plant and Clostridium butyricum DSM 10702. The influence of the incubation temperature and the carbon source composition were evaluated in order to select the best production profile according to the characteristics of the microalgal biomass. C. butyricum showed a clear preference for monomeric sugars and starch, the latter being the major storage compound in microalgae. The highest H2 production reached by this strain from starch was 468 mL/g, whereas the mixed culture incubated at 37 C (LE37) produced 241 mL/g. When the mixed culture was incubated at 58 C (LE58), a significant increase in the H2 production occurred when xylose and xylan were used as carbon and energy source. The highest H2 yield reached by the LE37 culture or in co-culture with C. butyricum was 1.52 and 2.01 mol/mol of glucose equivalents, respectively. However, the ratio H2/CO2 (v/v) of the biogas produced in both cases was always lower than the one produced by the pure strain. In kinetic assays, C. butyricum attained 153.9 mL H2/L h from S. obliquus biomass within the first 24 h of incubation, with a H2 yield of 2.74 mol/mol of glucose equivalents. H2 production was accompanied mainly by acetate and butyrate as coproducts. In summary, C. butyricum demonstrated a clear supremacy for third generation bioH2 production from S. obliquus biomass

Resources recovery from domestic wastewater by a combined process: anaerobic digestion and membrane photobioreactor

ABSTRACT: Anaerobic and membrane technologies are a promising combination to decrease the energy consumption associated with wastewater treatment, allowing the recovery of resources: organic matter as biomethane, nutrient assimilation by microalgae and reclaimed water. In this study, domestic wastewater was treated using a combination of an upflow anaerobic sludge blanket sludge reactor (UASB) and a membrane photobioreactor (MPBR). The outdoor facilities were operated continuously for three months under unfavourable environmental conditions such as lack of temperature control, winter season with lower solar irradiation and lower daylight hours which was a challenge for the present work, not previously described. The energetic valorisation of the organic matter present in the wastewater by biomethane produced in the UASB would contribute to reducing overall facilities’ energy requirements. The ultrafiltration (UF) membrane facilitated the harvesting of biomass, operating at 10 L·h−1·m−2 during the experimental period. Although the main contribution to fouling was irreversible, chemical cleanings were not necessary due to effective fouling control, which prevented the final TMP from exceeding 25 kPa. In addition, microalgae-bacterial consortium developed without prior inoculation were harvested from the MPBR using membrane assistance. The obtained biomass was also successfully tested as a biostimulant for corn germination/growth, as well as a biopesticide against Rhizoctonia solani and Fusarium oxysporum.info:eu-repo/semantics/publishedVersio

Microalgae biomass harvesting by electrocoagulation

The use microalgae biomass for the production of biofuels has received great attention in the last decades. Microalgae biofuels could be important alternative to conventional biofuels since microalgae could be produced at high rates without the need of neither arable land, potable water or competition with food. However, the high energy intensive harvesting processes are limiting the commercial production of microalgae biofuels. In this study, Electro-Coagulation (EC) was used for harvesting the freshwater microalga Chlorella vulgaris and the marine microalga Nannochloropsis sp. The results show that EC could be an alternative to the conventional harvesting processes since it is efficient and produces good quality biomass with low energy requirements

Scenedesmus obliquus in poultry wastewater bioremediation

ABSTRACT: Wastewater biological treatment with microalgae can be an effective technology, removing nutrients and other contaminants while reducing chemical oxygen demand. This can be particularly interesting for the meat producing industry which produces large volumes of wastewater from the slaughtering of animals and cleaning of their facilities. The main purpose of this research was the treatment of poultry wastewater using Scenedesmus obliquus in an economical and environmentally sustainable way. Two wastewaters were collected from a Portuguese poultry slaughterhouse (poultry raw - PR and poultry flocculated - PF) and the bioremediation was evaluated. The performance of microalga biomass growth and biochemical composition were assessed for two illumination sources (fluorescent vs LEDs). S. obliquus achieved positive results when grown in highly contaminated agro-industrial wastewater from the poultry industry, independently of the light source. The wastewater bioremediation revealed results higher than 97% for both ammonium and phosphate removal efficiency, for a cultivation time of 13 days. The saponifiable matter obtained from the biomass of the microalga cultures was, on average, 11% and 27% (m/malga) with PR and PF wastewater, respectively. In opposition, higher sugar content was obtained from microalgae biomass grown in PR wastewater (average 34% m/malga) in comparison to PF wastewater (average 23% m/malga), independently of the illumination source. Therefore, biomass obtained with PR wastewater will be more appropriate as a raw material for bioethanol/biohydrogen production (higher sugar content) while biomass produced in PF wastewater will have a similar potential as feedstock for both biodiesel and bioethanol/biohydrogen production (similar lipid and sugar content).info:eu-repo/semantics/publishedVersio