• Energy Research

Abstract In this paper the lignin gasification by using water in supercritical was studied. The employed lignin was produced via steam explosion of Arundo Donax after alkaline extraction and filtration. The lignin, with a total solid content of about 4 wt% in a solution of sodium hydroxide which confers to the solution a pH of about 11, was fed in a continuous PFR bench scale reactor able to operate at supercritical water conditions. The experiments were carried out at 550 °C and 250 bar by varying the feed flow rate from 10 mL/min to 60 mL/min in order to understand the effect of the residence time on the liquid and solid phases in terms of volume composition, liquid phase composition, carbon and global gasification efficiency. The main results showed that by using lignin after alkaline extraction, syngas with a higher heating value (HHV) greater than 40 MJ/kg without CO2, mainly composed by hydrogen and methane, was obtained. At the same time, in the liquid phase the presence of some compounds, such as glucose, syringaldehyde, formic acid, acetic acid and xylose, was revealed, and all these species are included in the main building block group for the green chemistry or for the development of bioprocess for high added value intermedia production.

Astaxanthin and lutein, antioxidants used in nutraceutics and cosmetics, can be extracted from several microalgal species. In this work, investigations on astaxanthin and lutein extraction from Haematococcus pluvialis (H. pluvialis) in the red phase were carried out by means of the supercritical fluid extraction (SFE) technique, in which CO2 supercritical fluid was used as the extracting solvent with ethanol as the co-solvent. The experimental activity was performed using a bench-scale reactor in semi-batch configuration with varying extraction times (20, 40, 60, and 80 min), temperatures (50, 65, and 80 °C) and pressures (100, 400, and 550 bar). Moreover, the performance of CO2 SFE with ethanol was compared to that without ethanol. The results show that the highest astaxanthin and lutein recoveries were found at 65 °C and 550 bar, with ~18.5 mg/g dry weight (~92%) astaxanthin and ~7.15 mg/g dry weight (~93%) lutein. The highest astaxanthin purity and the highest lutein purity were found at 80 °C and 400 bar, and at 65 °C and 550 bar, respectively.

Temporary rivers are characterized by dry-wet phases and represent an important water resource in semi-arid regions worldwide. The fate and effect of contaminants have not been firmly established in temporary rivers such as in other aquatic environments. In this study, we assessed the effects of sediment amendment with Polycyclic Aromatic Hydrocarbons (PAHs) on benthic microbial communities. Experimental microcosms containing natural (Control) and amended sediments (2 and 20 mg PAHs kg(-1) were incubated for 28 days. The PAH concentrations in sediments were monitored weekly together with microbial community structural (biomass and phylogenetic composition by TGGE and CARD-FISH) and functional parameters (ATP concentration, community respiration rate, bacterial carbon production rate, extracellular enzyme activities). The concentration of the PAH isomers did not change significantly with the exception of phenanthrene. No changes were observed in the TGGE profiles, whereas the occurrence of Alpha- and Beta-Proteobacteria was significantly affected by the treatments. In the amended sediments, the rates of carbon production were stimulated together with aminopeptidase enzyme activity. The community respiration rates showed values significantly lower than the Control after 1 day from the amendment then recovering the Control values during the incubation. A negative trend between the respiration rates and ATP concentration was observed only in the amended sediments. This result indicates a potential toxic effect on the oxidative phosphorylation processes. The impoverishment of the energetic resources that follows the PAH impact may act as a domino on the flux of energy from prokaryotes to the upper level of the trophic chain, with the potential to alter the temporary river functioning.

Haematococcus pluvialis microalgae in the red phase can produce significant amounts of astaxanthin, lutein, and fatty acids (FAs), which are valuable antioxidants in nutraceutics and cosmetics. Extraction of astaxanthin, lutein, and FAs from disrupted biomass of the H. pluvialis red phase using carbon dioxide (CO2) in supercritical fluid extraction (SFE) conditions was investigated using a bench-scale reactor in a semi-batch configuration. In particular, the effect of extraction time (20, 40, 60, 80, and 120 min), CO2 flow rate (3.62 and 14.48 g/min) temperature (50, 65, and 80 °C), and pressure (100, 400, and 550 bar.) was explored. The results show the maximum recovery of astaxanthin and lutein achieved were 98.6% and 52.3%, respectively, at 50 °C and 550 bars, while the maximum recovery of FAs attained was 93.2% at 65 °C and 550 bars.

Abstract The aim of the paper is based on the experimental tests of Gasification in supercritical water for humid biomass, Scenedesmus dimorphus. In this work, experimental tests were carried out in order to understand the main parameters of the SCWG process and their influence varying the total solids content, GGE and CGE gas yield and energy recovery. Based on experimental test and considering literature data about energy demand for microalgae growth and energy required for SCWG process it was possible to evaluate that with minimum total solid content necessary for setting-up a self-sustainable process considering the only energy recovery from the condensation of the water outlet the process. At the same time these simulation were repeated considering of use the enthalpy of water in SCW condition for turbine expansion instead heat recovery obtained not only syngas production usable for biofuels synthesis but also power production.