CO2 Sequestration by Chlorella vulgaris Using Cost-Effective Cultivation Media under Varying CO2 Concentrations in a Photobioreactor
Ghiffarin Priambudi, Wahyunanto A Nugroho*, Akhmad Adi Sulianto, Yusuf Wibisono

Biosystem Engineering, Brawijaya University

Abstract

Indonesia^s rapid population growth has driven the deforestation of approximately 10.2 million hectares and contributed 21.1 billion tons of CO2 emissions over the past two decades, highlighting the urgent need for effective carbon capture strategies. Microalgae such as Chlorella vulgaris offer a sustainable solution for CO2 sequestration due to their superior photosynthetic efficiency and adaptability. This study investigates the growth and CO2 fixation performance of C. vulgaris cultivated in three different media: standard BG-11 (M1), hydroponic fertilizer AB Mix (M2), and AB Mix supplemented with urea and TSP (M3), all selected for their ease of preparation and low cost. The cultures were exposed to three CO&#8322- injection levels-0.05% (C1), 1% (C2), and 5% (C3)-in a 12 L closed photobioreactor system. Growth rate, CO&#8322- fixation rate, and mass transfer rate were assessed across all treatments. The highest average specific growth rate was achieved in C1M2 (0.1481 day^-1), while the highest CO&#8322- fixation rate was observed in C3M2 (3567.792 mg L^-1day^-1), and the highest mass transfer rate in C3M3 (63.779 mg L^-1). Interestingly, treatments with low CO2 concentrations supported higher growth, whereas higher CO2 levels significantly enhanced fixation and transfer rates. A paired t-test revealed a statistically significant difference between specific growth and fixation rates (P < 0.05), while two-way ANOVA and Tukey HSD tests confirmed that CO&#8322- concentration and medium type significantly influenced fixation performance, though not growth. These results demonstrate the effectiveness of AB Mix-based media as low-cost alternatives to conventional media, supporting their potential for scalable microalgal CO2 sequestration systems, particularly in resource-limited settings.

Keywords: Chlorella vulgaris- CO2 sequestration- alternative cultivation media

Topic: Agricultural and bioprocess engineering