Investigation of the effects of variable pH & CO2 injection on the biomass growth of Chlorella vulgaris for sustainable microalgae cultivation

Abstract

Microalgae, photosynthetic organisms that produce organic compounds from carbon fixation, are increasingly important for sustainability and achieving Sustainable Development Goals (SDGs). However, their production is limited due to nutritional and environmental conditions like pH and CO2 concentration in nutrient solutions. This research investigated the growth of Chlorella vulgaris microalgae under different pH levels and CO2 injections. Results showed that all chemical parameters showed a decreasing tendency under different conditions. The highest biomass growth was achieved with CO2 injections, with the highest chlorophyll concentration. However, the injected CO2 significantly decreased the microalgae activity rate. Variable pH also had a significant effect on biomass growth, with neutral pH (7) resulting in the highest chlorophyll concentration. Alkaline pH (9.6, 10.2, and 11.0) could stimulate biomass increase in the first 10 days. Combining CO2 injection with an alkaline pH nutrient solution could shorten cultivation time and increase biomass generation, contributing to sustainability.