Renewable Biofuel Production Using Red Ginseng Marc in Microbial Fuel Cells

Microbial fuel cell (MFC) is one of the clean and sustainable energy technologies, often referred to as renewable energy, and directly chemical energy contained in organic matter into electrical energy by using the catalytic activity of microorganisms. Cellulosic biomass is a particularly attractive renewable resource for its abundant supply at low cost and its neutral carbon balance. However, methanogenesis had been negatively linked to anaerobic cellulosic power generation in MFCs. Ginseng root is a saponin-rich plant material and red ginseng marc (RGM) has not been reused as a high-value resource for industry although its residue contained both electron donors and saponin, the potential power generation enhancers for MFC. In this study, RGM was supplemented into MFC to evaluate its effects on methanogenesis and power generation. Two-chamber H-type MFCs were established using rumen fluid as anolyte to ferment cellulose at 2% (w/v). RGM, the residue from the steam and press process for red ginseng beverage preparation, was freeze-dried and ground to pass 0.5 mm sieve and added to the anode of MFC at 1% (w/v;Exp. 1) or 0.1% (Exp. 2) dose for treatment. Open circuit voltage, voltage and current across an external resistor were measured daily for 10d. On d10 of operation, collected biogases were measured for total gas production and analyzed for its components. In Exp. 1, power density was between 44.0 and 97.2 with an average of 83.8 mW/m2 in 1% RGM MFCs and was between 45.2 and 76.3 with an average of 61.5 mW/m2 in control. In Exp. 2, power density was between 44.8 and 75.6 with an average of 60.9 mW/m2 in 0.1% RGM MFCs and was between 45.1 and 54.1 with an average of 49.7 mW/m2 in control. Total gas production for 10d was 563 and 523 mL for RGM and control, respectively, in Exp 1, and was 546 and 477 mL for RGM and control, respectively, in Exp 2. Methane took up 58.6 and 67.9% of total gas for RGM and control, respectively, in Exp 1, and 59.1 and 67.3% of total gas for RGM and control, respectively, in Exp 2. Both greater (P < 0.05) power generation less (P < 0.05) methane proportion in RGM MFCs in both Exp. 1 and 2 strongly supports the potential use of red ginseng marc as MFC supplements.