Unlocking pilot-scale green diesel production from microalgae.

Microalgae have emerged as a promising source of biomass to produce renewable biofuels due to their ability to synthesize high-energy density compounds of commercial interest. This study proposes an approach for pilot-scale oil extraction, purification by fractional distillation, hydrocarbon characterization by gas chromatography coupled to mass spectrometry (GC-MS), evaluation of physicochemical parameters of the produced hydrocarbons, preliminary cost analysis, and challenges and future opportunities for green diesel on a commercial scale. Here, the microalgae Tetradesmus obliquus was cultivated in 12 m³ photobioreactors using biodigested swine waste as a culture medium. The resulting biomass was subjected to drying and harvesting, followed by oil extraction using a hot solvent extraction method, followed by distillation to purify the compounds. Three different extraction and distillation experiments were conducted, each using different solvent combinations. The results obtained revealed that extraction with a solvent blend, composed of hexane and ethanol, provided more significant yields compared to extraction with pure hexane. GC-MS analysis showed the presence of alkanes and alkenes in the oil samples, and the proportion of solvent used in the extraction directly influenced the production of alkanes. Additionally, specific hydrocarbons such as 4-methyl-1-decene, 8-heptadecene, 1-pentadecene, 9-heneicosene, and 2-dodecene were identified. The evaluation of the physicochemical parameters demonstrated that the calorific value of the distilled oil samples is within the range of typical values for petroleum diesel. However, it was observed that the distilled oil samples had higher sulfur content compared to conventional diesel. Regarding the cost analysis, it was found that it varies depending on the experimental conditions. In particular, the process using a solvent mixture of 70% hexane and 30% ethanol proved to be more economical than the others, since it extracted a greater quantity of oil with a lower initial biomass requirement. In summary, this microalgae-derived hydrocarbon production process is promising and offers insights for compound purification and future biofuel applications.

Environmental evaluation of flocculation efficiency in the separation of the microalgal biomass of Scenedesmus sp. cultivated in full-scale photobioreactors.

In this paper the environmental evaluation of the separation process of the microalgal biomass Scenedesmus sp. from full-scale photobioreactors was carried out at the Research and Development Nucleus for Sustainable Energy (NPDEAS), with different flocculants (iron sulfate - FeCl3, sodium hydroxide - NaOH, calcium hydroxide - Ca(OH)2 and aluminum sulphate Al2(SO4)3, by means of the life cycle assessment (LCA) methodology, using the SimaPro 7.3 software. Furthermore, the flocculation efficiency by means of optical density (OD) was also evaluated. The results indicated that FeCl3 and Al2(SO4)3 were highly effective for the recovery of microalgal biomass, greater than 95%. Though, when FeCl3 was used, there was an immediate change in color to the biomass after the orange colored salt was added, typical with the presence of iron, which may compromise the biomass use according to its purpose and Al2(SO4)3 is associated with the occurrence of Alzheimer's disease, restricting the application of biomass recovered through this process for nutritional purposes, for example. Therefore, it was observed that sodium hydroxide is an efficient flocculant, promoting recovery around 93.5% for the ideal concentration of 144 mg per liter. It had the best environmental profile among the compared flocculant agents, since it did not cause visible changes in the biomass or compromise its use and had less impact in relation to acidification, eutrophication, global warming and human toxicity, among others. Thus, the results indicate that it is important to consider both flocculation efficiency aspects and environmental impacts to identify the best flocculants on an industrial scale, to optimize the process, with lower amount of flocculant and obtain the maximum biomass recovery and decrease the impact on the extraction, production, treatment and reuse of these chemical compounds to the environment. However, more studies are needed in order to evaluate energy efficiency of the process coupled with other microalgal biomass recovery technologies. In addition, studies with natural flocculants, other polymers and changes in pH are also needed, as these are produced in a more sustainable way than synthetic organic polymers and have the potential to generate a biomass free of undesirable contaminants.

Thermal response of rats to different types of trauma.

BACKGROUND: Hypothermia is commonly observed in victims of trauma, and it is generally combined with shock caused by either hemorrhagic or nonhemorrhagic mechanisms. This study deals with phenomena related to nonhemorrhagic mechanisms. The objective is to document through experimental evidence the existence of a natural mechanism in rats that compensates for the inadequate tissue perfusion in the presence of shock by reducing body temperature (hypothermia). METHODS: Different types of trauma are analyzed (i.e., abdominal cavity and bowel exposure) and compared with other groups that suffered, additionally, femur fracture and partial hepatectomy. Further thermal alterations are also studied as consequences of vascular phenomena involving the elevation of intra-abdominal pressure and clamping of arteries and veins, such as the aorta and inferior vena cava. The loss of energy and temperature response of the animals is documented in time through charts with experimental uncertainties. RESULTS: It is concluded that exposure of the bowels is the main factor involved in the genesis of hypothermia, regardless of the associated trauma. Plastic film is shown to be the most effective way to avoid heat loss in bowel exposure. An optimal intra-abdominal pressure, Popt congruent with 12 mm Hg, is found such that heat flux loss is minimum in pneumoperitoneal procedures. CONCLUSION: Aortic and inferior vena cava clamping induces hypothermia at levels comparable to bowel exposure.

Avaliação da hipotermia em ratos submetidos a lesões medular experimental / Hypothermia evaluation in rats submitted to spinal cord injury

A fase aguda da lesäo medular cursa com importante disfunção autonômica, sendo a perda da termorregulaçäo um dos sintomas mais drásticos desta disfunção. Sabe-se que o lesado medular perde o controle da temperatura abaixo do nível lesado, com grande risco para o desenvolvimento de hipotermia. A incidência de hipotermia na fase aguda da lesão medular é desconhecida, o que leva a má compreensão deste quadro. Baseados nesses conceitos, os autores testaram um método para mensurar a perda de energia corp¢rea em ratos submetidos a lesäo medular experimental. Utilizaram modelo já padronizado de lesäo medular (NYU Impactor) e um transdutor esofágico para avaliar a variaçäo da temperatura central na primeira hora ap¢s a lesäo medular. Concluem que há diferença significativa na perda de energia entre o rato lesado medular e o grupo controle, e que o método de mensuraçäo esofágica é válido, apesar de suas limitaçäes