Biogas Production from Anaerobic Codigestion of Microalgae and Septic Sludge

Microalgae have been well recognized as one of the clean and renewable biomass energy resources. Codigestion using different cosubstrates has been shown to improve the anaerobic digestibility of microalgae and increase the biogas yield and methane content. This study investigated the effectiveness of using septic sludge as a cosubstrate to anaerobically digest microalgae. After 30days of co digestion at 35 degrees C, the codigestion group (25% algae, 50% algae, and 75% algae) had an average biogas production of 547.3 +/- 35.6mL/gVSfed, an amount that more than tripled the biogas production from the 100% algae group. The addition of septic sludge to the microalgae resulted in more favorable initial carbon to nitrogen ratios (C/N) (11:1 to 27:1), improved digestibility of algal biomass, and decreased hydrogen concentrations, which were directly related to the increased quantity and quality of methane produced. The results demonstrated the effectiveness of using septic sludge as a cosubstrate to anaerobically digest microalgae Chlorella sp. and enhance the biogas production. (C) 2016 American Society of Civil Engineers.