The Influence of Anaerobic Digestion Effluents (ADEs) Used as the Nutrient Sources for Chlorella sp. Cultivation on Fermentative Biogas Production

Abstract

Purpose: This study investigated the chemical characteristics and anaerobic digestion of Chlorella sp. microalgae cultivated on various anaerobic digestion effluents (ADEs) as a nutrient medium. Chlorella sp. was grown in anaerobically digested effluent of dairy wastewater (DW), municipal wastewater sludge (WS), maize silage and swine slurry, and cattle manure (CM). Methods: To evaluate the anaerobic biodegradability of harvested biomass, 20-days batch anaerobic digestion experiments were used. Results: It was found that a nutrient medium directly affected nitrogen concentration in the cultivated biomass, as well as the C/N ratio value which ranged 7.2–12.9. Higher C/N ratio of the Chlorella sp. cultivated on DW and WS significantly enhanced the methane production, which was 241 ± 5.5 mL CH4/g VS and 267 ± 10.9 mL CH4/g VS, respectively. The highest biogas production rate of 61.28 ± 2.7 mL/g VS·d and methane concentration in biogas of 69.7 ± 4.1 % were obtained during the digestion of Chlorella sp. biomass cultivated on WS. Conclusions: These results proved the applicability of ADEs as a nutrient medium for Chlorella sp. cultivation and the impact of a nutrient source on C/N ratio in harvested biomass, which subsequently affected the biogas/methane yield.