Novel Hydrogen Cell Factories for Sustainable Energy Generation and Wastewater Management

Abstract This study aims to evaluate the feasibility of using a renewable and cost-effective system called Microbial Electrolysis Cell (MEC) for produced water (PW) treatment while recovering energy in the form of hydrogen gas. The generated hydrogen can serve as an energy-neutral/positive source for waste treatment in the gas-oil-separation plant (GOSP). Additionally, the output water, with reduced oil content, can be repurposed for re-injection operations to support reservoir pressure and for fracturing operations. This study aims to identify key parameters that impact MECs performance for PW treatment. The assessment included a detailed analysis of the PW treatment process, focusing on (1) microbial community analysis of the electroactive biofilm and metabolic pathways; (2) testing different applied voltages while monitoring electroactive biofilm growth through chronoamperometry and cyclic voltammetry; and (3) conducting abiotic control and open circuit voltage (OCV) control experiments. A sampling protocol was developed to systematically collect inoculum from industrial environments. This protocol aimed to enrich microbial communities capable of degrading specific contaminants in PW, thereby enhancing their effectiveness in the microbial electrolysis process. MEC oxidize organic carbon contaminants at the anode, releasing electrons that are used to generate energy in the form of hydrogen gas at the cathode. The energy required to drive the reaction in the MEC is lower than the conventional voltage required for water splitting (i.e., 1.8–3.5 V). Hence, the process can be powered by renewable energy sources, such as wind or solar, which enhances the plant's water handling capacity. This study explores different testing strategies and reactor configurations to optimize PW treatment and hydrogen production from enriched microbial communities. which could be further optimized for larger-scale applications. In light of the industrial efforts towards energy mix and transition, MEC technology can generate green electricity with low CAPEX to design and construct the bioreactor in the field, and helps to address one of the pressing business and environmental challenges in the upstream operations by (1) Providing clean energy-neutral source from PW; (2) Generating non-damaging water for injection and fracturing operations; (3) Unlocking oil potential by increasing plant capability in handling water. It also includes an analysis of energy consumption and energy balance. The samples were processed for microbial communities profiling through DNA Nanopore sequencing technology and bioinformatic canalysis, revealing novel microbial species that are crucial for MEC performance. Additionally, analytical and electrochemical assessments helped in identifying suitablesetups for producing electrical current in MECs fed with PW and Disposal Water (DW), as well as optimal methods for contaminants breakdown. The varying concentrations of PW and DW (0.5-3%) generated electrical current in MECs, indicating their potential as energy sources, demonstrating that both PW and DW contain sufficient organic matter to support bio-electrochemical processes, which could be further optimized for larger-scale applications. In light of the industrial efforts towards energy mix and transition, MEC technology can generate green electricity with low CAPEX to design and construct the bioreactor in the field, and helps to address one of the pressing business and environmental challenges in the upstream operations by (1) Providing clean energy- neutral source from PW; (2) Generating non-damaging water for injection and fracturing operations; (3) Unlocking oil potential by increasing plant capability in handling water.