Abstract:
The waste biomass substrates for microbial fuel cell (MFC) were tested using a batch
type MFC. The performances of each cell were measured individually by recording
the Open Circuit Voltage (OCV) against time using three different substrates; cow
dung, coconut water and glucose. The cell was operated using an aerated cathode for
waste substrates. A chemical cathode was used for defined substrate. The
relationship for the voltage generation with the nutrients (in terms of Chemical
Oxygen Demand (COD)) and the availability of electricigens was discussed for both
defined and waste substrates. The highest of the average of mean OCV was observed
for glucose (0.35V) and for waste substrates it varied from 0.18V to 0.28V. Coconut
water had a higher COD compared to cow dung even though the availability of the
electricigens was unknown.
Each step in electricity generation in MFC was studied and the parameters which
affected power generation were identified. Dimensional analysis was done to the
selected parameters using the “Buckingham Pie” theorem and a set of dimensionless
groups was calculated. The physical meaning behind each of the dimensionless
groups was analysed. Using the dimensionless groups, a polynomial equation was
developed as follows:
Da = α (μ/ρ)a (d3gρ2/μ2)b (h/d)c
Where, D is the mass diffusivity (m2s-1),μ viscosity (kgm-1s-1),ρ density (kgm-3) ,d
distance between the two electrodes (m), h height of the electrode (m), g
gravitational constant (ms-2) and α, a, b, c are constants.
This equation is useful in finding the relationship between the operational parameters
when the MFC is operating at its highest power density with no forced convection of
the electrolyte. Using a set of experiments, the values of the constants can be found,
with those values the equation is important in the process of scaling up of the
microbial fuel cell.
