Effects of Temperature and Other Operational Parameters on Chlorella vulgaris Mass Cultivation in a Simple and Low-Cost Column Photobioreactor.

Abstract

Mass production of microalgae worldwide, and even more so in developing countries, is strongly contingent upon the availability of economical and efficient photobioreactors (PBRs) that are amenable for use in resource-limited environments. Such options are limited. This work assesses the effects of temperature, CO2 enrichment, and mixing by air + CO2 bubbling on Chlorella vulgaris biomass production in a simple, low-cost 84-L column PBR. Cultivation at 25, 30, and 35 °C in a batch process showed that biomass production was negatively affected above 30 °C. Specific growth rates at each temperature were 0.75, 0.76, and 0.63 day(-1), respectively, with batch productivities of 70.50, 81.67, and 35.83 mg L(-1) day(-1). While a relatively low CO2/air ratio (1 %) seemed beneficial during the early stages of cultivation, higher concentrations were required to maintain growth rate and achieve higher biomass concentrations around 1000 mg L(-1). Cultivation with air + CO2 bubbling rates of 100, 200, and 400 L h(-1) led to specific growth rates (and batch productivities) of 0.64 day(-1) (59.58 mg L(-1) day(-1)), 0.74 day(-1) (81.67 mg L(-1) day(-1)), and 0.80 day(-1) (86.67 mg L(-1) day(-1)), respectively. The results indicate that high biomass productivities of C. vulgaris can be obtained up to 30 °C with moderate (2 %) to high (10 %) CO2 in a fairly simple PBR.