A promising alternative to petroleum-derived fuels lies in microalgae-produced biodiesel. Compared to major terrestrial crops, microalgae have higher rates of oil and biomass production and appear to be the only source of renewable biodiesel that can meet global demand for transport fuels. Chlorella vulgaris may be suitable for biodiesel production due to its faster growth and easier cultivation compared to other strains. Lipid production is achieved in two steps: a biomass production phase, and a lipid production phase, in which the lipid content of algal cells is increased by submitting them to environmental stress such as nitrogen starvation. As a preliminary step towards the optimization of the biomass production step, the effect of different nutrient concentrations in TAP medium on the photobioreactor cultivation of C. vulgaris was studied. The results showed good growth of Chlorella vulgaris in 2X TAP, reaching a biomass concentration of 6.0 g/liter. Growth inhibition was observed at concentrations of the nitrogen source, NH4Cl, between 500 and 1000 mg/liter in the medium. Varying the concentration of the phosphorus source, K2HPO4 in the medium had no effect on cell growth within the range studied, provided phosphorus sufficiency is ensured. Other medium components are non-limiting at the levels studied.Link.
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Semi-continuous Cultivation of Chlorella vulgaris for Treating Undigested and Digested Dairy Manures
The present study, based on a previous batch-wise experiment, investigated a lab-scale semi-continuous cultivation of green microalgae Chlorella vulgaris (UTEX 2714), as a useful means for nutrient reduction as well as production of algal biomass which can be used as potential feedstock for the production of biofuel and other commodities, on 20x diluted dairy manures. Both undigested and digested samples were applied in parallel experiments for comparison regarding the requirements of hydraulic retention times (HRTs), removal efficiencies of nitrogen, phosphorus, and chemical oxygen demand (COD), biomass productivities, and CO(2) sequestration abilities. It was demonstrated that algae grown in undigested dairy manure achieved removal rates of 99.7%, 89.5%, 92.0%, and 75.5% for NH (4) (+) -N, TN, TP, and COD, respectively, under a 5-day HRT, while the HRT had to extend to 20 days in order to achieve 100.0% removal of NH (4) (+) -N in digested one with simultaneous removals of 93.6% of TN, 89.2% of TP, and 55.4% of COD. The higher organic carbon contained in undigested dairy manure helped boost the growth of mixotrophic Chlorella, thus resulting in a much shorter HRT needed for complete removal of NH (4) (+) -N. Moreover, algae grown in digested dairy manure provided more penitential than those grown in undigested one in CO(2) sequestration per milligram of harvested dried biomass (1.68 mg CO(2)/mg dry weight (DW) vs 0.99 mg CO(2)/mg DW), but did not surpass in total the amount of CO(2) sequestered on a 15-day period basis because of the better productivity gained in undigested dairy manure.Link.
Guess I'm going to be interested in algae this weekend. What about everyone else?