Effects of Light, Co2 and Reactor Design on Growth of Algae: An Experimental Approach to Increase Biomass Production
Year: 2014
Type: dissertation
Abstract: The increase in atmospheric carbon dioxide concentrations and resulting global climate change coupled with the high cost of fossil fuels are encouraging the search for alternative sources of fuels and methods to produce food without using agricultural land. Algal biomass production has the potential to address these problems; algae are rich in fats, proteins and carbohydrates. Algae fix carbon dioxide and are relatively easy to grow. They can be grown in both fresh and marine water. Algal oil can be used as a feedstock to make biodiesel, the omegas and antioxidants can be used as food supplements and components of medicines; the proteins can be used for animal feedstock and food suppliments; and the carbohydrates can be used to produce ethanol. Study of the factors affecting growth of microalgae play a critical role for the development of efficient methodologies for harvesting their products. Experiments were conducted with six algae to evaluate effects of light source, CO2 concentration and reactor design; small bubble column versus flat panel photo-bioreator. Light treatments that supplemented artificial light with daily solar radiation at 4614 mg L-1 resulted in 15% more biomass production than those treatments that provided 24 h of artificial illumination (4016 mg L-1) during 49 days of incubation.Treatments with Chlorella vulgaris during 15 d that combined continuous exposure from LEDs emitting blue + red radiation (430 and 625 nm) and from white light resulted in greater biomass production, 1003 mg L-1 and 1045 mg L-1, respectively, than those from a single light source (red at 571 mg L-1 and blue at 828 mg L-1). Growth of Nannochloris sp and Scenedesmus sp during 13 d of incuabion exposed to flashing lights in a bubble column photo-bioreactor resulted in more biomass production (1041 mg L-1 and 1130 mg L-1, respectively) and higher cell weight than those algae growing under continuous light (892 mg L-1 and 1018 mg L-1, respectively. Experiments with bubble column photo-bioreactors and Chlorella vulgaris growing under increasing CO2 concentrations, from 0.035% to 8.5%, during a 15 d incubation increased biomass production from 148 mg L-1 to 1592 mg L-1. A flat panel, industrial scale photo-bioreactor resulted in biomass production of 2337 mg L-1 during 15 d, which was significantly more than that obtained in bubble column reactors. This research has shown that algal biomass production can be increased when grown under illumination that supplemented solar radiation with artificial light during the night time. An increase in the concentration of CO2 supplied to the algae increased algal biomass production 10 fold. Exposure as light dark cycles, the flashing effect, which utilitzes 85-90% less energy consumption than exposure to continuous light, resulted in greater biomass productiont. A light path less than 5 cm resulted in increased biomass production by >1.5 fold. Algae growing in a flat panel bioreactor developed the highest biomass production, and the research suggests that this bioreactor design can be a reliable system for growing algae at a large scale.
Author: Sebastian Mejia Rendon
Language: English
Field: Energy
Domain: Physical Sciences
Open Access status: green
Funder: Government of Canada
OpenAlex ID: W2640706328