In situ hydrogen production in power-to-food applications

Abstract

Technologies capable of coupling sustainable generation of energy and production of valuable products are required to shift the focus from a fossil economy to a renewablebased and circular economy and to confront environmental pollution. In this regard, hybrid biological–inorganic (HBI) systems, which combine the advantages of biological components with electrochemical methods, provide a platform for efficient and sustainable chemical synthesis. HBI technology can be used to synthesize a wide range of highvalue compounds, including microbial proteins, alcohols, and polymers. The operating principle of HBI systems is based on the use of special autotrophic microorganisms in systems with in situ water electrolysis, which are interfaced to biocompatible electrodes. These biocompatible catalysts or electrodes are then employed to convert electrical energy into H2 or energetic reducing equivalents, which are then used by microorganisms as an energy source for assimilation of CO2 to create new carbonaceous molecules. In this context, HBI systems are anticipated to play a critical role in storing energy from intermittent energy sources, as well as offering a sustainable mechanism for fixing CO2.

With HBI being a nascent technology, this doctoral dissertation aims to study and improve the energy efficiency of in situ water electrolysis and to prove the feasibility of CO2 assimilation into protein-rich biomass on a pilot scale. To achieve these goals, the performance of different conventional electrodes and transition metal electrocatalysts is comparatively studied in specific electrolytes used in HBI processes. So far, as the practical implementation of HBI systems requires the development of robust and scalable electrobioreactors, this work reports a series of in situ water electrolyzer stack designs as part of an electrobioreactor system. In addition, this research presents a Neo-Carbon Food concept that demonstrates pilot-scale synthesis of microbial biomass using direct CO2 capture from the air, autotrophic bacteria, and in situ water electrolysis. The data collected during the experiments could be employed to simulate, investigate, and improve electrobioreactors with in situ water electrolysis used in HBI processes. The results attained in this research represent a significant step for the industrial implementation of HBI systems.