Abstract
Microbial fuel cell (MFC) is one of renewable biofuel production technology that directly converts biomass to electricity. Cellulosic biomass is particularly attractive renewable resources for its low cost and abundance and neutral carbon balance. However, methanogenesis remains as a major factor limiting MFC performance. The current study reports that saponin addition at 0.05% w/v dose to anolyte in MFCs inhibited methanogenesis and improves power generation and cellulose fermentation. Mediator-less two chamber H-type MFCs were prepared using rumen fluid as anode inocula at 20% v/v of anolyte to convert finely ground pine tree (Avicel) at 2%, w/v to electricity. Saponin was added to the anode of MFC at 0.005% or 0.05% v/v dosage for treatment. MFC power and current across an external resistor were measured daily for 10d. On d10, collected gases from anode compartment were measured for total gas volume and analyzed for gas composition on gas chromatography. Supplementation of saponin to MFC at 0.005% did not have any effects on electricity generation or biogas production and composition. Saponin at 0.05% dose reduced 10% of methane production and increased 40% of CO2 production and 6.4% of total gas production for 10d MFC operation. Voltage across resistor prior to treatment addition (d0) was 164.75 ± 9.07 mV. In control group, voltage across resistor did not change (P = 0.9153) with time course and mean was 167.8 ± 8.20 mV ranged from 157 to 174.5 mV during 10d operation. In 0.05% Saponin group, voltage across resistor increased (P 0.0001) after d2 and mean was 187.3 ± 4.30 mV ranged between 161.5 and 204.0 mV and the 10d mean of voltage across resistor in 0.05% Saponin was greater (P 0.0001) than in control group. 0.05% Saponin also had greater voltage across resistor at d5 (P = 0.0030) and d6 (P = 0.0246) than control. End point potential increased (P 0.0001) in 0.05% Saponin after d2. 0.05% Saponin had greater (P 0.0001) in 0.05% Saponin. Power density increased (P 0.0001) after d2 in 0.05% Saponin. 0.05% Saponin MFCs had greater (P 0.0001) overall mean of 10d operation. The current study provides strong background for potential use of saponin and saponin containing natural resources for methanogenesis inhibitor and cellulolysis enhancer in MFC and also cellulolysis reactors.
Highlights
Fossil fuels represented about 80% of the global energy use [1], and fossil fuel combustion and natural gas and petroleum systems for energy contributed 95.3% of greenhouse emission in the USA [2] which cause global warming and pollutions [3]
The current study reports that saponin addition at 0.05% w/v dose to anolyte in Microbial fuel cell (MFC) inhibited methanogenesis and improves power generation and cellulose fermentation
The current study provides strong background for potential use of saponin and saponin containing natural resources for methanogenesis inhibitor and cellulolysis enhancer in MFC and cellulolysis reactors
Summary
Fossil fuels represented about 80% of the global energy use [1], and fossil fuel combustion and natural gas and petroleum systems for energy contributed 95.3% of greenhouse emission in the USA [2] which cause global warming and pollutions [3]. Microbial fuel cell (MFC) is one of renewable biofuel production technology that directly converts biomass to electricity [5] MFC has shown tremendous electron donor versatility including simple substrates like glucose and organic acids [6] [7], complex substrates such as municipal and industrial wastewaters [8] [9]; and cellulosic biomass [10] [11]. To utilize cellulosic biomass in MFC, the anodic process requires cellulose degradation, but electrochemically active microorganisms did not possess cellulolytic activity, cellulose fermentation by cellulolytic microorganisms is required as electron donors to generate electricity [15] [16]. Methanogens in anaerobic microbial community contribute significantly to limiting cellulosic power generation in MFC. Methanogenesis diverts electron from the anode and methanogens act as substrate competitors to the exoelectrogens, acetoclastic methanogens compete for electron donors, and hy-
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