Enhanced methane yields from anaerobic digestion of Arthrospira maxima biomass in an advanced flow-through reactor with an integrated recirculation loop microbial fuel cell

Abstract

A semi-continuously fed continuous stirred tank reactor (CSTR), advanced flow-through anaerobic reactor (AAR) and advanced flow-through anaerobic digester with an integrated recirculation loop microbial fuel cell (ADMFC) were investigated for the production of methane using Arthrospira maxima as the sole feedstock. The study demonstrated that the inclusion of a recirculation loop MFC increased the methane yields and so energy efficiency of anaerobic digestion of Arthrospira maxima biomass. The semi-continuously fed CSTR operating under a hydraulic retention time (HRT) of 10 days and an organic loading rate (OLR) of 0.5 g DW per L⁻¹ d⁻¹ concluded a maximum methane yield of 90 ± 19 mL CH₄ per g VS with an energy efficiency of 17.1 ± 0.8%. The continuous phase AAR and ADMFC units were operated with HRTs ranging from 2 to 4 days and organic loading rates varying from 0.5 to 3 g DW L⁻¹ d⁻¹. The maximum methane yield and energy efficiency concluded from the ADMFC unit was 173 ± 38 mL CH₄ per g VS and 29.7 ± 6.8% respectively, whilst that of the AAR was 136 ± 16 mL CH₄ per g VS and 22.1 ± 2.6%.