Performance evaluation of a continuous-flow bioanode microbial electrolysis cell fed with furanic and phenolic compounds

Abstract

Furanic and phenolic compounds, formed during the pretreatment of lignocellulosic biomass, are problematic byproducts in down-stream biofuel processes. A microbial electrolysis cell (MEC) is an alternative technology to handle furanic and phenolic compounds and produce renewable hydrogen (H₂). The present study evaluated the performance of a continuous-flow bioanode MEC fed with furanic and phenolic compounds at different operating conditions. All hydraulic retention times (HRTs) tested (6–24 h) resulted in complete transformation of the parent compounds at an organic loading rate (OLR) of 0.2 g L⁻¹ per d and applied voltage of 0.6 V. Increasing the OLR to 0.8 g L⁻¹ per d at an HRT of 6 h resulted in an increased H₂ production rate from 0.07 to 0.14 L L_anode⁻¹ per d, but an OLR of 3.2 g L⁻¹ per d did not lead to a higher H₂ production rate. Significant methane production was observed at an OLR of 3.2 g L⁻¹ per d. The lack of increased H₂ production at the highest OLR tested was due to a limited rate of exoelectrogenesis but not fermentation, evidenced by the accumulation of high acetate levels and higher growth of fermenters and methanogens over exoelectrogens. Increasing applied voltage from 0.6 to 1.0 V at an OLR of 3.2 g L⁻¹ per d and HRT of 6 h enhanced exoelectrogenesis and resulted in a 1.7-fold increase of H₂ production. Under all operating conditions, more than 90% of the biomass was biofilm-associated. The present study provides new insights into the performance of continuous-flow bioelectrochemical systems fed with complex waste streams resulting from the pretreatment of lignocellulosic biomass.