Page 219 - Refining Biomass Residues for Sustainable Energy and Bioproducts

Generation of bioenergy from industrial waste using microbial fuel cell technology 189

electrodes have been widely used for MFCs. Surface area of the electrode is an
important parameter in the generation of electricity. In MFC the electrode materials
have different characteristics, and their support materials may have some important
characteristics such as good conduction, fine chemical stability, high mechanical
strength, and more importantly low cost. Carbon materials and noncorrosive metals
are most widely used base materials. However, some specific requirements, such as
high biocatalytic activity, high surface roughness, good biocompatibility, and effi-
cient electron transfer between bacteria and electrode surface, are necessary.
Electrode surface modification has become an emerging topic of interest in the
research field of MFCs. The air-cathode electrode material is fabricated by using a
base material, a catalyst, a binder, and a waterproof coating.

8.6.2 Effect of spacing between anode and cathode on power
production

An important parameter that has a high influence on total power production is spac-
ing between the electrodes. The total power production increased when the spacing
between the anode and cathode are at less distance. Ahn et al. (2014) found that
2
maximum power density of 10.9, 8.6, and 7.4 mW/m was observed at electrode
spacing 20, 24, and 28 cm, respectively, in their research. It is also observed that
maximum power density was observed at larger spacing. At external resistance
between 900 and 1200 Ω, maximum power density was observed and power density
decreased with increase in resistance beyond 1200 Ω.

8.6.3 Effect of electrode surface area on power production
Electrode surface area has a significant influence on power production in MFC.
The electric power generation in MFCs is predicted to increase with an increase of
electrode surface area. Cathode area influences on MFC outputs with hydrogen and
by bacteria, whereas anode area does make such impact. Cathodic reaction is a
rate-limiting reaction and air-cathode and PEM used in many MFC research. MFC
performance may purely depend on cathode reaction, whereas anode reaction may
be just pulled forward by the cathode reaction.

8.6.4 Influence of microorganisms in microbial fuel cell
The literature evidenced that numerous microorganisms have the capacity to trans-
fer electrons derived from organic matters’ metabolism to the anodic region. The
sources of such microorganism are marine sediment, soil, wastewater, and activated
sludge. A molecular breeding of bacteria optimized to the MFC environment is also
important for the enhancement of the MFC outputs. The anodic electron transfer
mechanism in MFC is a key issue in understanding the theory of how MFC’s work.
Under anaerobic conditions in soils and sediments, Geobacter belongs to dissimila-
tory metal reducing microorganisms, which produce biologically useful energy in