6 Microbial Fuel Cells: A Green and Alternative Source …
93
6.3 Factors Affecting Bioenergy from MMFCs
Several factors are contributing effectively to the MMFC’s efficiency and production
of bioenergy. The most common factors include substrate, bacterial and algae species,
metabolism activity of the organism, mechanism of electron transfer in an anodic
chamber and electrodes materials and surface area. Besides, factors such as pH,
temperature, salinity, and electron acceptor in a cathodic chamber are considered
as the most important factors in the operating process and they affect directly on
the algal and bacterial growth and activity, and thus on the MMFC’s performance
(Aghababaie et al. 2015).
6.3.1 Effect of Substrate
In many studies, the wastewater is used as a substrate for bacterial and algae growth
due to the high contents of nutrients and organic compounds which support the organism growth and acts as a source for electrons required for generating the bioenergy.
Several wastewater such as tannery, slaughterhouse, rice mill, swine, cassava mill,
dairy, winery, and molasses wastewater have been used as a substrate for bioenergy production by MFCs (Min et al. 2005; Zhang et al. 2009; Kaewkannetra et al.
2011; Mshoperi et al. 2011; Mardanpour et al. 2012; Katuri et al. 2012; Mathuriya
2013; Sciarria et al. 2015). However, fresh market wastewater is the best medium
for bacterial and algae growth and also for handling. This is because the fresh market wastewater has high contents of nutrients required for algae growth and rich
with organic materials required for bacterial growth and honors for electrons besides
having low suspended solids (SS) in comparison to the sewage wastewater. The
low concentrations of SS might also support the algae growth because the sunlight
can penetrate the wastewater and provide the light required for the anabolism and
metabolism activity in the algae cells.
Velasquez-Orta et al. (2011) investigated the efficiency of brewery, bakery, dairy,
and paper industrial wastewater in producing bioenergy by MFCs. The study revealed
that MFCs fed with paper wastewater generated the highest current density (125 ±
2 mA/m
2 ), while dairy wastewater produced 25 ± 1 mA/m
2 . In contrast, the brewery
and bakery wastewaters produced only 10 ± 1 mA/m
2 . The authors claimed that the
current production was independent of substrate degradability, while the microbial
composition of anodic biofilms differed based on the wastewater. The MFC anodes
with paper wastewater exhibited the redox activity at −134 ± 5 mV. In comparison
with the commercial substances, Chae et al. (2009) tested four types of fed substrates
including acetate, butyrate, propionate, and glucose in MFCs with anaerobic sludge.
The study found that the Coulombic efficiency (CE) was dependent on the substrate,
and ranged from 72.3% in the presence of acetate to 15.0% with glucose.
93
6.3 Factors Affecting Bioenergy from MMFCs
Several factors are contributing effectively to the MMFC’s efficiency and production
of bioenergy. The most common factors include substrate, bacterial and algae species,
metabolism activity of the organism, mechanism of electron transfer in an anodic
chamber and electrodes materials and surface area. Besides, factors such as pH,
temperature, salinity, and electron acceptor in a cathodic chamber are considered
as the most important factors in the operating process and they affect directly on
the algal and bacterial growth and activity, and thus on the MMFC’s performance
(Aghababaie et al. 2015).
6.3.1 Effect of Substrate
In many studies, the wastewater is used as a substrate for bacterial and algae growth
due to the high contents of nutrients and organic compounds which support the organism growth and acts as a source for electrons required for generating the bioenergy.
Several wastewater such as tannery, slaughterhouse, rice mill, swine, cassava mill,
dairy, winery, and molasses wastewater have been used as a substrate for bioenergy production by MFCs (Min et al. 2005; Zhang et al. 2009; Kaewkannetra et al.
2011; Mshoperi et al. 2011; Mardanpour et al. 2012; Katuri et al. 2012; Mathuriya
2013; Sciarria et al. 2015). However, fresh market wastewater is the best medium
for bacterial and algae growth and also for handling. This is because the fresh market wastewater has high contents of nutrients required for algae growth and rich
with organic materials required for bacterial growth and honors for electrons besides
having low suspended solids (SS) in comparison to the sewage wastewater. The
low concentrations of SS might also support the algae growth because the sunlight
can penetrate the wastewater and provide the light required for the anabolism and
metabolism activity in the algae cells.
Velasquez-Orta et al. (2011) investigated the efficiency of brewery, bakery, dairy,
and paper industrial wastewater in producing bioenergy by MFCs. The study revealed
that MFCs fed with paper wastewater generated the highest current density (125 ±
2 mA/m
2 ), while dairy wastewater produced 25 ± 1 mA/m
2 . In contrast, the brewery
and bakery wastewaters produced only 10 ± 1 mA/m
2 . The authors claimed that the
current production was independent of substrate degradability, while the microbial
composition of anodic biofilms differed based on the wastewater. The MFC anodes
with paper wastewater exhibited the redox activity at −134 ± 5 mV. In comparison
with the commercial substances, Chae et al. (2009) tested four types of fed substrates
including acetate, butyrate, propionate, and glucose in MFCs with anaerobic sludge.
The study found that the Coulombic efficiency (CE) was dependent on the substrate,
and ranged from 72.3% in the presence of acetate to 15.0% with glucose.