**3. Agro-Industrial Wastewater as a Substrate for Microbial Fuel Cells**

Generally, agro-food processing waste is comprised of a large number of organic constituents, which can be either in a solid, liquid, or gaseous state. For example, carbohydrates, fat, etc., present in wastewater, indicate the need for the maximum oxygen demand for biodegradation [67]. Various solids in the wastewater are known to halt or reduce the MFCs efficiency. Severe pollution challenges can occur to the environment when there is an absolute lack of proper treatment or management of such agro-industrial wastewater [66,68]. Conventionally, agricultural activities lead to the production of different amounts of food debris and wastes from either man or animal due to various activities

derived directly from the human or animal population, which contribute significantly to effluent discharged into receiving streams [69]. The agricultural production streams that usually produce agricultural residues and wastewater require several treatments to avoid water pollution, which enormously varies in pollutant composition and concentration. Some effluent from various agro-industries and their suitability for use in MFCs is discussed in subsequent subsections.
