RESUMO
The interest in microalgae production deals with its role as the third generation of feedstock to recover renewable energy. Today, there is a need to analyze the ultimate research and advances in recovering the microalgae biomass from the culture medium. Therefore, this review brings the current research developments (over the last three years) in the field of harvesting microalgae using membrane-based technologies (including microfiltration, ultrafiltration and forward osmosis). Initially, the principles of membrane technologies are given to outline the main parameters influencing their operation. The main strategies adopted by the research community for the harvesting of microalgae using membranes are subsequently addressed, paying particular attention to the novel achievements made for improving filtration performance and alleviating fouling. Moreover, this contribution also gives an overview of the advantages of applying membrane technologies for the efficient extraction of the high added-value compounds in microalgae cells, such as lipids, proteins and carbohydrates, which together with the production of renewable biofuels could boost the development of more sustainable and cost-effective microalgae biorefineries.
RESUMO
ABSTRACT The cultivation of microalgae is a possible destination for vinasse, a residue from the sugar and alcohol industry. This use can help reduce the costs of microalgae production and remediate this residue rich in nutrients. However, the physicochemical characteristics of vinasse limit its use for microalgae growth at low concentrations, except when the residue is pretreated. This work aimed at optimizing the vinasse pretreatments of centrifugation and adsorption by smectite clay and activated charcoal on laboratory scale in terms of amounts of materials used and time spent, making them more viable on larger scales. The optimized processes were then compared in productive, economic, and environmental terms. The dilution of treated vinasse with distilled water resulted in similar growth of Chlorella vulgaris to those obtained with the dilution in BG11 medium, indicating that the addition of nutrients in culture media is not necessary. Although microalgae growth occurs in higher concentrations of vinasse treated by adsorption, the results show that centrifugation required less processing time, has cheaper processing costs, and generated much less residue. Centrifugation treatment has greater economic and environmental viabilities and was more sustainable than the adsorption, even though the algae did not grow in the centrifuged residue in concentrations as high as it did after the adsorption treatment. Therefore, this article brings a new view about the economic and environmental aspects on the use of pretreated vinasse for microalgal growth, giving a lucrative destination for a highly polluting waste.
RESUMO O cultivo de microalgas é um possível destino para a vinhaça, um resíduo da indústria sucroalcooleira. Esse uso pode ajudar a reduzir custos da produção de microalgas, além de remediar esse resíduo rico em nutrientes, entretanto as características físico-químicas da vinhaça limitam seu uso para o crescimento de microalgas a baixas concentrações, exceto quando o resíduo é pré-tratado. Este trabalho objetivou otimizar os pré-tratamentos da vinhaça de centrifugação e de adsorção por argila esmectita e carvão ativado em escala laboratorial quanto à quantidade de materiais utilizados e tempo gasto, tornando-os mais viáveis em escalas ampliadas. Os processos otimizados foram então comparados em termos produtivos, econômicos e ambientais. A diluição das vinhaças tratadas com água destilada resultou em crescimento de Chlorella vulgaris semelhante ao obtido com diluições com meio BG11, indicando que a adição de nutrientes nos meios de cultura não é necessária. Embora o crescimento de microalgas ocorra em concentrações mais altas de vinhaça tratada por adsorção, os resultados mostram que a centrifugação exigiu menos tempo de processamento, tem custos mais baratos e gerou menos resíduos. De maneira comparativa, o tratamento por centrifugação possui maior viabilidade econômica e ambiental e foi mais sustentável do que a adsorção, embora as algas não tenham crescido no resíduo centrifugado em concentrações tão altas quanto após o tratamento de adsorção. Portanto, este artigo traz uma nova visão sobre os aspectos econômicos e ambientais do uso da vinhaça pré-tratada para o crescimento de microalgas, proporcionando um destino lucrativo para um resíduo altamente poluente.
RESUMO
ABSTRACT A total of 480 Arbor Acres Broiler chicks (mixed sex) from 1 to 35 days of age were divided randomly into 4 treatments to evaluate the impact of defatted Scenedesmus obliquus biomass (DAB) on broiler performance. The DAB was supplemented to broiler diets with levels of 0, 0.25, 0.50, 1.00% from one-day-old to 35 days of age. The DAB samples were analyzed in triplicates. The productive traits were measured weekly and the biochemical indices at the end of the trial. Data was statistically analyzed by One-way ANOVA. It was found that slaughter body weight, body weight gain and average daily feed intake were increased in birds fed diets supplemented with DAB compared to the control ones. However, feed conversion ratio was not affected by any of the treatments. Broilers serum enzymes activities and markers indicated that liver function as indicated by aspartate transaminase (AST) and alanine transaminase (ALT) and kidneys function which indicated by serum creatine and urea were not affected by DAB supplementation. Furthermore, protein, glucose and cholesterol levels in broilers serum were in normal levels and not affected by treatments. No significant changes were observed in relative organ weights (spleen, bursa, liver, gizzard, proventriculus and heart) or intestine length of broilers at 35 days of age in response to DAB supplementation in their diets. It could be concluded that DAB supplementation to broiler diets from 1 to 35 days of age up to 1% had no negative impacts and might have had a positive effect on broiler performance at 35 days of age.
RESUMO
This study evaluated the effect of high-rate ponds (HRPs) of different depths (20, 30 and 40â cm) on the carbon assimilation by microalgae cultivated in domestic sewage. The efficiency of the dissolution provided by the carbonation column and the carbon release to the atmosphere through the movement of the paddle wheels were also investigated. Dissolution efficiencies of 50%, 48% and 46% were obtained in the HRPs of 20, 30 and 40â cm depth, respectively. These differences can be attributed to the time necessary to recirculate the volume of each HRP in the carbonation column. The volumetric mass transfer coefficients regarding the release to the atmosphere were 0.0007, 0.0005 and 0.0004â min-1 for the 20, 30 and 40â cm HRPs, respectively. The carbon assimilation by the biomass was inversely proportional to depth, with values of 90%, 72% and 68% for the 20, 30 and 40â cm HRPs, respectively. Chlorophyll-a concentration was also higher in the 20â cm HRP. The radiation attenuation at the beginning of the operation was similar among the treatments, resulting in a greater fraction of the pond depth with available radiation in the 20â cm HRP.