Relationship Between Algae Biomass, Light Intensity, and Biofuel Production

Abstract

Microalgae are a source that has received significant research interest as a potential third generation biofuel source due to their capacity to achieve a high lipid accumulation potential, grow fast and not compete with food crops for land use. Despite the fact that light intensity has been identified as one of the most important environmental parameters that influence algal photosynthesis, biomass accumulation, and efficiency of biofuel production, quantitative relationships between light dose, biomass, and biofuel production efficiency are not fully documented for commercially relevant algal species. In this experimental research, these relationships are explored for three commonly studied microalgae, namely Chlorella vulgaris, Spirulina platensis and Nannochloropsis sp., under controlled laboratory conditions under five different light intensities (50, 150, 250, 350 and 450 µmol photons m⁻² s⁻¹). The biomass production was quantified using a dry weight analysis after 48 hours, every 48 hours for 21 days, and biofuel yield was determined using a Bligh-Dyer lipid extraction method and transesterification. Pearson correlation and multiple regression (R2 = 0.874 and p < 0.001) showed a significant positive correlation between light intensity and biomass yield, but photoinhibition caused a decrease in productivity beyond the saturation threshold. The highest lipid content was obtained from Chlorella vulgaris under medium-high light intensity (400µmol m-2 s-1) while Nannochloropsis sp. showed better performance under lower intensity light. The results have implications for the design of photobioreactors and optimizing biofuel production systems for outdoor algae cultivation in large-scale.