Cellular respiration is one of the fundamental biological processes necessary for life. During this metabolic reaction, cells convert biochemical energy from nutrients into adenosine triphosphate (ATP). The process involves breaking down molecules and freeing electrons. The movement of these electrons affords opportunities for energy production.
Microbial fuel cells (MFCs) capitalize on the respiration process by collecting the electrons released by bacteria. Inside a fuel cell, the bacteria on an anode metabolizes organic matter, breaking it down into hydrogen ions, carbon dioxide, and electrons. The electrons flow from the anode to the cathode through a wire, generating an electrical current. Hydrogen passes through a permeable membrane to the cathode to combine with dissolved oxygen and ions to form H2O.
In theory, any substance able to be metabolized by microorganisms can function as the feedstock for a microbial fuel cell. Therefore, urban sewage, agricultural or food waste, as well as various industrial wastewaters can be utilized as a valuable material. When used in wastewater treatment plants, MFCs simultaneously treat water while producing electricity.
A recent report by Micro Market Monitor indicates that key drivers of the microbial fuel cell market are an ever-increasing demand for energy, interest in sustainable industry, and the need for resource conservation. According to the report, “The global microbial fuel cell market is projected to grow from an estimated USD 9.0 million in 2017 to USD 18.6 million by 2025, at a CAGR of 9.5% from 2017 to 2025.”
However, there are a number of factors limiting the market’s growth as well. Researchers cite inconsistent power production and low power density as factors that have restricted the number of MFC installations worldwide.
A 2017 study conducted by Li He, Peng Du, et al. titled Advances in Microbial Fuel Cells for Wastewater Treatment evaluated some of the primary challenges for MFCs in wastewater treatment including scalability and power output. In order to boost the economic feasibility of such projects, the study suggests the integration of MFCs with other distributed energy resources within a treatment plant’s energy network.
In a separate study, V.G. Gude explains that, “MFC technology represents a unique and novel platform to process waste and wastewater sources that allows for energy and resource recovery along with water sanitation in a single configuration. They have the potential to provide the paradigm shift for wastewater treatment from ‘environmental protection’ to ‘resource recovery.’”
What are your thoughts? Do you think that microbial fuel cells could be transformative for wastewater treatment? What needs to happen in order for this technology to gain momentum?