Microbial fuel cells (MFCs) indeed use living organisms, such as bacteria or algae, as catalysts to generate electricity from certain substrates. These microorganisms break down organic matter and transfer electrons to an electrode, creating an electric current. While MFCs primarily use organic substrates for electricity generation, they may also utilize some inorganic materials, but this is less common. MFCs can indeed be installed in wastewater treatment plants to cleanse water through microbial degradation of organic pollutants, while simultaneously producing electricity. This dual functionality makes them a sustainable source of energy.