Zero-discharge, self-sustained 3D-printed microbial electrolysis cell for biohydrogen production: a review

Microbial fuel cell (MFC) and microbial electrolysis cell (MEC) technologies have been used recently in bench-scale bioenergy (electricity) generation, biohydrogen (H₂) production, biosensing, and wastewater treatment. There are still a lot of obstacles to overcome in terms of commercialization and industrial settling. These difficulties include lengthy start-up times, intricate reactor designs for managing large reaction volumes, and expensive and time-consuming large-scale system fabrication procedures. Interestingly, combining three-dimensional (3D) printing with MFC and MEC technology appears to be a workable and promising way to get past these obstacles. Moreover, a rapid start-up with no delays in the current generation using MFC and MEC is possible with 3D printed bio-anodes. Furthermore, H₂ can be generated from wastewater by powering a stacked MFC and MEC-coupled with electrochemical capacitor (ECC) system using 3D printing technology. To the best of the author's knowledge, this review paper is the first to explicitly highlight the use of 3D printing in creating a stacked MFC–ECC–MEC system in conjunction with a photobioreactor (PBR) to produce significant quantities of H₂ and carbon dioxide (CO₂) can be utilized for algae production. A notable feature of 3D printing technology is its reliable production capabilities, enabling MFC–ECC–MEC–PBR systems to be expanded by setting up numerous stacks of MFC–ECC–MEC–PBR units devoid of material waste and human error. The present review attempts to provide an update on the current status of the 3D printing application, that is meant to propel the MFC–ECC–MEC–PBR system forward.