Comparative analysis of cultivation methods for

Microalgae are promising third-generation biofuel resources, but large-scale cultivation is often limited by the high cost of fertilizers. This study evaluates the growth and nutrient recovery efficiency of C. vulgaris using palm oil mill effluent (POME) as a nutrient-rich medium under three cultivation methods: heterotrophic, photo-heterotrophic, and mixotrophic. The results show that mixotrophic cultivation achieved the highest nutrient recovery, removing 85.55% of chemical oxygen demand (COD), 46.92% of phosphorus, and 55.48% of total nitrogen (TN) from 1 vol% POME. Additionally, mixotrophic conditions significantly enhanced the lipid, carbohydrate, and protein yields in the microalgae biomass, with lipid yield being particularly high, making it suitable for biofuel production. Utilizing POME as a growth medium provides a sustainable alternative to conventional fertilizers, lowering cultivation costs and contributing to the circular economy within the palm oil industry. These findings demonstrate the potential of mixotrophic cultivation to improve both nutrient recovery and biomass quality, supporting the broader application of microalgae for biofuel production and environmental management.