Process modeling and 3-stage photobioreactor design for algae cultivation and CO2 capture: A case study using palm oil mill effluent

Abstract

Microalgae have advantages, including rapid growth rates, a high lipid production capacity, effective removal of nitrates and phosphates from wastewater, and efficient carbon dioxide (CO₂) absorption. The optimal operating conditions and strategies of microalgae cultivation can vary significantly from one goal to another. An economic approach to exploring various operating strategies is doable via microalgal process modeling and simulation. Therefore, this study aims to develop a simulation model aimed at enhancing algae growth within a photobioreactor (PBR) system designed to reduce CO₂ emissions in palm oil mills. This simulation model is constructed to explore the algae growth CO₂ capture efficiency and the influence of oxygen (O₂) in the water in the PBR. This study achieved a CO₂ capture efficiency of up to 60 % which represents the highest capture, and a dissolved O₂ of 20 % was achieved due to the effect of the mass transfer coefficient. Algal growth exhibited a high rate, approximately 1057 g/m³, which could serve as a potential pathway for biodiesel or biobutanol production. Additionally, this study underscores the significant role of the mass transfer coefficient in effectively reducing liquid O₂ levels to maximize CO₂ capture and achieve a high algae yield. Furthermore, the simulation results reveal that a high concentration of O₂ in the water promotes photorespiration, which hampers algal growth and reduces CO₂ capture efficiency.