Utilisation of C. asymmetrica in biogas upgrading: A proof of concept

A significant step towards meeting the rising global energy demand is the utilisation of organic waste streams for energy generation. The process of anaerobic digestion results in the production of biogas, which is composed primarily of methane and carbon dioxide. However, the presence of impurities in biogas requires the upgrading process to meet the requisite utilisation standards. This study examines the potential of photoautotrophic biogas upgrading using the microalgae Chlamydomonas asymmetrica to remove CO 2 . A batch cultivation in sealed bottles with a nutritional medium containing dissolved biogas was conducted. The results indicate that C. asymmetrica is capable of tolerating and growing at high pH values, reaching a maximum of 10.98. The growth curves exhibited an initial lag phase, followed by exponential and stationary phases, which correlated with CO 2 availability. The recovery of CO 2 in biomass was evaluated, with experimental data indicating that C. asymmetrica can grow in CO 2 concentrations up to 35 %, with maximum CO 2 fixation rates of up to 0.400 g L −1 d −1 . These findings highlight the potential of C. asymmetrica in biogas upgrading, thereby contributing to the development of a more sustainable and economically viable bioenergy sector. • C. asymmetrica high pH resistant. • High potential of C. asymmetrica for application in biogas upgrading. • Comparison of CO 2 fixation rates with values from existing literature.