Optimization of microalgal production in a shallow outdoor flume

Abstract

The marine diatom Cyclotella cryptica was grown over a period of 13 months in a 48-m(2) shallow outdoor flume. The use of foil arrays at intervals of 1.2 m to effect systematic vertical mixing in the flume was found to significantly enhance microalgal production (p = 0.006). Average photosynthetic efficiencies (based on visible irradiance) with and without the foil arrays in place were 9.6 +/- 0.8 and 7.5 +/- 0.5% (+/-95% confidence intervals), respectively. A cost-benefit analysis indicated that the foil arrays were cost-effective if the value of the algae exceeded about $2.28 kg(1) of ash-free dry weight (AFDW). Parallel experiments performed in four 9.2-m(2) flumes showed that production was maximized when the cells were grown on a 2-day batch cycle between harvests rather than on a 1- or 3-day batch cycle. The optimum initial concentration (immediately after harvesting) of the algae was negatively correlated with the time interval between harvests and ranged from approximately 39 g AFDW/m(3) on a 3-day cycle to 213 g AFDW/m(3) on a 1-day cycle. The increase in production resulting from growth on a 2-day rather than a 1-day batch cycle was about 19% and was statistically significant at p = 0.0003. Growth of C. cryptica over a total period of 122 days during the 13-month study in the 48-m(2) flume under near-optimal conditions (2-day batch cycle, initial concentration 155 g AFDW/m(3)) resulted in an average production rate (+/-95% confidence interval) of 29.7 +/- 2.7 g AFDW/m(2) d.

Systems and economic analysis of microalgae ponds for conversion of CO{sub 2} to biomass. Final report

“…The study included a comparison of paddle wheels with Archimedes screws and propellers; they were all similar in power inputs. Foils placed into the pond to stimulate turbulence increased productivities (see also Laws et al, 1983Laws et al, ,1986Laws et al, ,1988. Productivities were generally lower than in prior studies by this group, about 20 g biomass ash free dry weight/m2/day, possibly due to high respiratory losses.…”

Microalgal Reactors: A Review of Enclosed System Designs and Performances

“…Use of hollow fiber devices has been reported for culture of mammalian cells (78), in culture of the microalga Chlamydomonas reinhardtii (79), in continuous culturing of the microalga P. tricornutum in seawater (80), and in culture of the cyanobacteria Anabaena Variabilis (81). In regard to active mode, two main transfer processes are usually considered: (i) gas mixture is circulated together with culture, either injected at a certain point of the system (riser tube) (16,17,28,41,45,53,54,(82)(83)(84)(85)(86)(87)(88)(89)(90) or bubbled at the bottom of the reactor vessel (29-32, 34-36, 46, 51, 52, 55, 56, 61-63, 91, 92); or (ii) gas is inserted into the culture when it passes through a gas exchanger (44,50) (see Table 5). …”

Low algal diversity systems are a promising method for biodiesel production in wastewater fed open reactors

“…Bioenergy production from algae is promising because productivity is high per land area, producing almost 300 times more oil per acre than conventional crops (Laws et al 1988, Dalrymple et al 2013. Also algal cultivation does not compete with food production, algae have very fast growth rates which permit several harvests within a short time frame, and algae production absorbs CO 2 from the atmosphere.…”