94
A. A. S. Al-Gheethi et al.
6.3.2 Effect of Electrode Materials
Electrode materials represent a crucial role in the generation of bioenergy in many
of the studies. Tsai et al. (2009) tested the potential of carbon nanotube (CNT)
modified carbon cloth as an electrode in single-chamber MFCs with wastewater
as a substrate for the bacterial growth. The study revealed that the CNT coated
onto carbon cloth electrode has improved the power density to 65 mW m
−2 with
67% of the Coulombic efficiency. Lee and Huang (2013) investigated the effect of
electrode spacing (ES) with the range of 5.8–19.5 cm and substrate concentrations
in terms of COD (mg/L) on the electricity generation in MFCs. The study indicated
that the maximum bioenergy output 3 was 0.32 mW/m
2 recorded at ES 5.8 cm
and nominal COD (in) 300 mg COD/L. The study concluded that the ES required
for improving electricity generation is dependent on the level of COD. Wang et al.
(2017) developed SMFCs with comb-type cathode electrodes and carbon cloths. The
cathode electrode was studied with three different exposed areas to investigate their
effect on the improvement of oxygen transfer. The study revealed that the maximum
power density was 3.77 × 10
−2 mW/m
2 with 75% of the (M A75 ) exposed area,
while the lowest was recorded in the completely immersed electrode. The study
concluded that the exposed area of the cathode electrode plays a critical role in the
power performance of SMFCs. The effect of the presence of the cathode microporous
layers and the distance between cathode and anode on the performance of MFCs was
studied by Yao et al. (2014). The study revealed a correlation between power density
and the distance between cathode and anode, the power density has reduced from
973 to 797 mW/m
2 as a result of decrease in the distance from 2 to 1 cm. However,
the power generation increased to 955 mW/m
2 with 0 cm distance. The study also
revealed that the presence of aerobic bacteria might induce the non-linear correlation
between the power production and electrodes’ distance.
6.3.3 Effect of Bacterial and Algae Species and Density
Both bacterial and algae species and the initial concentrations used in MFCs play
important role in the production of bioenergy. Arbianti et al. (2017) investigated
the effect of microbial density (0–10%) by MFCs in producing bioenergy. The study
revealed that 1% of the bacterial density was generated between 291.1 mV and 66.33
mW m
−2 with 4.48% of the Coulombic efficiency. The nutrients were used as an effective energy source in MFCs by the bacterial cells as a biocatalyst. Nonetheless, many
of the bacterial species have been used in MFCs. Choo et al. (2006) listed these bacteria including Burkholderia multivorans, Pseudomonas aeruginosa, Acinetobacter
sp., Bacteroidetes, Actinobacteria, Cyanobacteria, Spirochaetes, β-Proteobacteria,
and α-Proteobacteria.
Mei et al. (2015) investigated the performance of bacterial density and community
from four sources including garden soil (GS), activated sludge (AS), river sediment
A. A. S. Al-Gheethi et al.
6.3.2 Effect of Electrode Materials
Electrode materials represent a crucial role in the generation of bioenergy in many
of the studies. Tsai et al. (2009) tested the potential of carbon nanotube (CNT)
modified carbon cloth as an electrode in single-chamber MFCs with wastewater
as a substrate for the bacterial growth. The study revealed that the CNT coated
onto carbon cloth electrode has improved the power density to 65 mW m
−2 with
67% of the Coulombic efficiency. Lee and Huang (2013) investigated the effect of
electrode spacing (ES) with the range of 5.8–19.5 cm and substrate concentrations
in terms of COD (mg/L) on the electricity generation in MFCs. The study indicated
that the maximum bioenergy output 3 was 0.32 mW/m
2 recorded at ES 5.8 cm
and nominal COD (in) 300 mg COD/L. The study concluded that the ES required
for improving electricity generation is dependent on the level of COD. Wang et al.
(2017) developed SMFCs with comb-type cathode electrodes and carbon cloths. The
cathode electrode was studied with three different exposed areas to investigate their
effect on the improvement of oxygen transfer. The study revealed that the maximum
power density was 3.77 × 10
−2 mW/m
2 with 75% of the (M A75 ) exposed area,
while the lowest was recorded in the completely immersed electrode. The study
concluded that the exposed area of the cathode electrode plays a critical role in the
power performance of SMFCs. The effect of the presence of the cathode microporous
layers and the distance between cathode and anode on the performance of MFCs was
studied by Yao et al. (2014). The study revealed a correlation between power density
and the distance between cathode and anode, the power density has reduced from
973 to 797 mW/m
2 as a result of decrease in the distance from 2 to 1 cm. However,
the power generation increased to 955 mW/m
2 with 0 cm distance. The study also
revealed that the presence of aerobic bacteria might induce the non-linear correlation
between the power production and electrodes’ distance.
6.3.3 Effect of Bacterial and Algae Species and Density
Both bacterial and algae species and the initial concentrations used in MFCs play
important role in the production of bioenergy. Arbianti et al. (2017) investigated
the effect of microbial density (0–10%) by MFCs in producing bioenergy. The study
revealed that 1% of the bacterial density was generated between 291.1 mV and 66.33
mW m
−2 with 4.48% of the Coulombic efficiency. The nutrients were used as an effective energy source in MFCs by the bacterial cells as a biocatalyst. Nonetheless, many
of the bacterial species have been used in MFCs. Choo et al. (2006) listed these bacteria including Burkholderia multivorans, Pseudomonas aeruginosa, Acinetobacter
sp., Bacteroidetes, Actinobacteria, Cyanobacteria, Spirochaetes, β-Proteobacteria,
and α-Proteobacteria.
Mei et al. (2015) investigated the performance of bacterial density and community
from four sources including garden soil (GS), activated sludge (AS), river sediment