RAS question
Microbial Fuel Cells (MFC) generate electricity from:
Correct answer: (B) Bacterial metabolism of organic matter.
Microbial fuel cells generate electricity when bacteria metabolise organic matter and transfer the released electrons to an electrode.
Explanation
Microbial fuel cells are bio-electrochemical devices, not conventional fuel cells. In them, bacteria oxidise organic matter such as wastewater, biomass or other biodegradable substrates. During this metabolism, exoelectrogenic microorganisms release electrons outside the cell; carbon anodes in MFCs act as external electron acceptors. Once those electrons move through the circuit to the electrode system, electrical current is produced. This is why bacterial metabolism of organic matter is the precise answer. The same principle applies with cellulose: electricity was generated from cellulose in an MFC using bacteria, confirming that biodegradable organic material can serve as the substrate for current generation.
Why the other options are wrong
- (A) Nuclear reactions involve changes in atomic nuclei, whereas MFCs use bacterial oxidation of biodegradable organic matter and electron transfer to an anode.
- (C) Wind energy is a mechanical renewable-energy source; an MFC produces current through microbial metabolism inside an electrochemical cell, not through moving air.
- (D) Sunlight is not the energy input described here; electricity generation in MFCs depends on bacteria using biodegradable substrates such as cellulose.
Concept
This tests biotechnology under Science and Technology, especially bio-electrochemical systems used for waste-to-energy applications. RAS often asks such concepts because they connect environmental management, renewable energy and applied microbiology.