Outdoor Large scale Microalgae consortium culture for biofuel production in South Africa: Overcoming adverse environmental effects on microalgal growth

Abstract

In nature, microalgal blooms occur regularly and in contrast with laboratory cultivation procedures, these blooms are not axenic and this seems to add to the longevity and intensity of the bloom. For this reason a consortium of microalgae and bacteria is used at InnoVenton for large scale biomass cultivation. The biomass produced, has successfully been used to produce biocrude. Laboratory cultivation procedures also require a large energy input in terms of artificial lighting, heating and aeration making it a costly endeavour. However, this stringent control of the culture to avoid contamination and ensure optimal growth conditions is essential when cultivating the microalgae for medical and pharmaceutical applications. When culturing for a chemical application such as biofuel production, this is not the case, therefore allowing for the economical outdoor consortium cultivation approach employed at InnoVenton. In this study we investigated whether morning heating of the media will overcome low consortium growth rates experienced in winter and whether the use of glucose, ethanol and acetate will overcome biomass loss exhibited at night. The results showed that heating increased the growth rate relative to those measured in summer and that heating all day in winter did not induce better growth rates in comparison to only heating for an hour at sunrise. We show that all three carbon sources are efficient at overcoming biomass loss at night with glucose being the most effective. In conclusion, employing these two techniques, the same growth rate theoretically can be achieved year round with large scale outdoor cultivation.

Keywords: consortium, microalgae, biocrude