This article reviews the applications and performance of microbial fuel cells as an alternative energy option. This technology involves using microorganisms, like bacteria, to oxidize biodegradable substrates as fuels through biological processes to produce electrons, which are then shuttled to an external electron acceptor ( anode), and transferred to a cathode via copper wire, thus producing electricity. The performance of a microbial fuel cell can be influenced by several factors. The performance of a microbial fuel cell, as well as other fuel cells, is determined by the current, power density, and rate of fuel oxidation. Various factors can influence the rate of fuel oxidation, including the anodic catalytic activity, fuel diffusion, and the diffusion and consumption of electrons and protons. A microbial fuel cell generates electricity directly from electron donors through the microbial activity. Electricity generation in microbial fuel cells is based on the metabolic activity of living microorganisms. This fact requires that such fuel cell systems have to run under conditions predefined by the optimum growth and living conditions of the utilized microorganisms. Thus, microbial fuel cells are usually operated at ambient temperature, atmospheric pressure, and at pH neutral or only slightly acidic conditions.