The combustion of fossil fuels significantly increases atmospheric carbon dioxide (CO₂), contributing to global climate change. Thus, renewable biofuel resources are essential to mitigate CO₂ emissions. Euglena sp., a microalga which is capable of CO₂ fixation, producing biomass that can be utilized for biofuel production. Additionally, microalgae can assimilate nutrients from liquid waste, such as palm oil mill effluent (POME), which is rich in essential elements for growth and lipid synthesis as part of a biorefinery approach. This study investigated the effects of POME supplementation at concentrations of 0%, 15% and 30% under mixotrophic and heterotrophic cultivation with 15% CO₂ injection on the morphology, growth, biomass, and metabolite content (lipids and paramylon) of Euglena sp. in the laboratory-scale culture. The M. 15% treatment (mixotrophic with 15% POME) yielded the highest performance, with a cell density of 1,458 × 10⁴ cells/mL, optical density of 0.52, biomass of 0.57 g/L and lipid content of 0.42 mg/L. The highest paramylon accumulation occurred in the H. 15% treatment (heterotrophic with 15% POME), reaching 4.516 ± 0.008 mg/L/day on day 15. The morphological analysis revealed that spindleshaped and elongated cells were found in most treatments, with heterotrophic 15% showing predominantly spindle shapes. The dominant fatty acid methyl esters (FAMEs) identified was methyl palmitoleate.