Biochemical Methane Potential of Microalgae Cultivated in High-Strength Beverage Wastewater: Implications for Energy Enhancement

This study aimed to assess the biochemical methane potential (BMP) of microalgal substrates grown on high-strength beverage wastewater as a potential end-use application for biomass. Two microalgal species, Scenedesmus obliquus and Chlorella pyrenoidosa, were cultivated in standard Blue Green-11 (BG-11) media and high-strength beverage wastewater with a COD of around 5,000 mg L−1. A BMP of 185.53 ± 2.66 mL CH4 g−1 VSadded was obtained from Scenedesmus grown in BG-11 media, which increased to 336.35 ± 26.56 mL CH4 g−1 VSadded after being grown in beverage wastewater. Similar increasing patterns were also observed in the case of Chlorella, where the BMP increased from 179.64 ± 4.14 to 245.51 ± 29.35 mL CH4 g−1 VSadded when changing the media from BG-11 to beverage wastewater. After lipid extraction, microalgae substrates yielded higher methane production, with 393.66 ± 41.08 and 421.86 ± 47.52 mL CH4 g−1 VSadded from Scenedesmus and Chlorella, respectively. Theoretical methane estimation from carbohydrate, protein, and lipid contents resulted in overestimating BMP. However, ANOVA statistics highlighted significant differences in experimental methane yields, and the modified Gompertz model validated the predicted BMP with the experimental values, with an R2 above 0.94. Overall, this study outlines the potential for biomethane enhancement from microalgae grown in wastewater, with an extended energy recovery opportunity after lipid extraction.