Bio-hydrogen production through microbial electrolysis cell: Structural components and influencing factors

Microbial electrolysis cell (MEC) is a significantly sustainable bio-electrochemical system for biological hydrogen production. MEC is also regarded as an environmentally friendly method for producing clean biohydrogen from a variety of waste organic matters and for its low greenhouse gas emissions. This technology involves the oxidation of organic matter at the anode and the reduction of proton at the cathode under the nominal external voltage supply. However, bio-hydrogen production efficiency and operating costs of MEC still need further optimization to implement in large-scale applications. For optimization, a detailed explanation of MEC components and major operational parameters should be available. This review discusses the principle, main components, and major operational parameters of MEC for significant performance. It also provides a brief overview of types of MECs, reactor configuration, and their advantages. Thermodynamically important aspects of the MEC for efficient performance are also discussed. It also conferred the critical structural components which are essential for the functioning MECs. Furthermore the performance evaluating parameters and indices for the biohydrogen yield and MEC performance are also addressed. Additionally, crucial influencing factors that affect the MEC performance such as microorganism, methanogens and their inhibition, various electrode materials, membranes and different substrates are also discussed. Afterwards needs and challenges for future development of the MEC technology are highlighted and suggested. The review aims to put forward the fundamental understandings of MEC technology to the research fraternity for further advancement for the large-scale applications.