Synthetic alkali soluble lignin supplementation to sucrose-rich wastewater fed mfc

Microbial Fuel Cells are bioelectrochemical devices exploiting exo-electrogenic bacteria for conversion of chemical energy in wastewater to electrical energy directly. Low power production is viewed as one of important bottle-neck in scaling-up microbial fuel cells. Rate of electron transfer by microbes to anode determines the total power produced from these units. Addition of external redox mediators capable of shuttling electrons from bacteria to anode had be extensively studied. But the toxicity and cost of operation discriminates its use in practical system. Lignin a plant polymer found abundant in agro-residues, ethanol hydrolysate and paper and pulp industry wastewater could mediate electrons from bacteria to anode. In our study we have utilised organics rich sugarcane baggase wash water from paper industry as primary substrate for microbial growth in anode chamber of MFC. Synthetic alkali soluble lignin was tested as mediator. There was a minor reduction in the peak Open Circuit Voltage (OCV) compared to 720mV for Baggase Wash Water (BWW) to 702mV for BWW+0.1mol/l lignin. The highest power density and current density with lignin addition was 93mW/m² and 273mA/m² respectively. The COD removal efficiency was 61%, whereas the Columbic efficiency was 22%. The increase in CE from 6% to 22% could be an effect electron mediating capacity and methanogen suppression by lignin in anode chamber.