The extraction of lipids from microalgae cells of Botryococcus braunii and Chlorella vulgaris after ultrasonic and microwave pretreatment was evaluated. Cell disruption increased the lipid extraction efficiency, and microwave pretreatment was more effective compared with ultrasonic pretreatment. The maximum lipid yield from B. braunii was 56.42% using microwave radiation and 39.61% for ultrasonication, while from C. vulgaris, it was respectively 41.31% and 35.28%. The fatty acid composition in the lipid extracts was also analyzed. The methane yield from the residual extracted biomass pretreated by microwaves ranged from 148 to 185 NmL CH4/g VS for C. vulgaris and from 128 to 142 NmL CH4/g VS for B. braunii. In the case of ultrasonic pretreatment, the methane production was between 168 and 208 NmL CH4/g VS for C. vulgaris, while for B. braunii ranging from 150 to 174 NmL CH4/g VS. Anaerobic digestion showed that lipid-extracted biomass presented lower methane yield than non-lipid-extracted feedstock, and higher amount of lipid obtained in the extraction contributed less methane production. Anyway, anaerobic digestion of the residual extracted biomass can be a suitable method to increase economic viability of energy recovery from microalgae.

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This paper presents data on methane fermentation of algal biomass containing Chlorella sp. and Scenedesmus sp. The biomass was obtained from closed-culture photobioreactors. Before the process, the algae were subjected to low temperature and pressure pretreatment for 0.0, 0.5, 1.0 and 2.0 h. The prepared biomass was subjected to mesophilic methane fermentation. The amount and composition of the biogas formed in the process were determined. The amount of biogas produced was larger when the biomass was subjected to thermal preprocessing. The proportion of methane in the gas also increased. Extending the heating time beyond 1.0 h did not significantly improve the biogassing effects.

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The aim of this study was to determine the effectiveness of dairy wastewater treatment in the integrated technology based on the simultaneous use of the activated sludge method (AS) and a hydrophyte system (HS) (AS-HS), in this case, common reed (Phragmites australis) or common cattail (Typha latifolia). Experiments were conducted in an innovative reactor exploited in the fractional-technical scale at the loads of 0.05 mg BOD5/mg.d.m. d (biochemical oxygen demand) and 0.10 mg BOD5/mg.d.m d. The AS--HS enabled improving the removal effectiveness ofbiogenes characterized by concentrations of Ntot., N-NH4 and Ptot. In contrast, the integrated system had no significant reducing effect either on concentrations of organic compounds characterized by BOD5 and chemical oxygen demand parameters or on the structure of AS in the sequencing batch-type reactors.

The objective of this study was to determine the possibility of using microalgae biomass from natural water bodies as a substrate for methane fermentation and to verify the effect of taxonomic structure and other physicochemical traits of the biomass on the technological effectiveness of the process. Harvested algae was characterized by a diversified taxonomic structure and on the content of nitrogen compounds and concentration of organic compounds in biomass, that was subject to seasonal dynamics of changes. The highest technological effects of the methane fermentation process were achieved with microalgae biomass harvested in July. In this period, the predominating taxonomic group were the Cyanoprokaryota, with a significant contribution of Chlorophyta. The mean yield of biogas production reached 441.15 ± 19.03 cm3/g o.d.m., at the mean production rate of r = 98.99 cm3/day and a reaction constant of k = 0.224 1/day. The mean content of methane in biogas accounted for 68.68 ± 1.67%. The lowest technological effects linked with biogas production were determined in November. These were the periods of the vegetative season with Bacillariophyceae constituting the predominating taxonomic group. The total production of biogas accounted for 333.65 ± 18.85 cm3/g o.d.m. The methane content were at mean levels of 54.19 ± 2.31%. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 858–865, 2015