Investigating the effect of hydrogen sulfide impurities on the separation of fermentatively produced hydrogen by PDMS membrane

In Situ Wide-Field Visualization of Palladium Hydrogenation

Visualizing hydrogenation processes in palladium (Pd) in real-time is important to various hydrogen-involved applications. However, observing hydrogen diffusion of Pd was limited by its small permittivity variation, and the kinetics of lateral diffusion of hydrogen in Pd film was not reported. Here, we proposed an optical microscopy-based visualization of Pd hydrogenation from the diffusion surface to the interior by introducing a fast-response mechanical platform that transforms the hydrogen diffusion into self-organized ordered wrinkles with sharp optical contrast. This platform is a Au/Pd double layer on an elastomer, which results in directional hydrogenation from the sidewall to the interior. The kinetics of hydrogenation in the interior of the palladium along the diffusion direction was monitored in real-time. This platform will enable in situ visualization of atom/ion diffusion on metals that are crucial in energy storage and hydrogen detection.

A New Perspective for Climate Change Mitigation—Introducing Carbon-Negative Hydrogen Production from Biomass with Carbon Capture and Storage (HyBECCS)

The greatest lever for advancing climate adaptation and mitigation is the defossilization of energy systems. A key opportunity to replace fossil fuels across sectors is the use of renewable hydrogen. In this context, the main political and social push is currently on climate neutral hydrogen (H2) production through electrolysis using renewable electricity. Another climate neutral possibility that has recently gained importance is biohydrogen production from biogenic residual and waste materials. This paper introduces for the first time a novel concept for the production of hydrogen with net negative emissions. The derived concept combines biohydrogen production using biotechnological or thermochemical processes with carbon dioxide (CO2) capture and storage. Various process combinations referred to this basic approach are defined as HyBECCS (Hydrogen Bioenergy with Carbon Capture and Storage) and described in this paper. The technical principles and resulting advantages of the novel concept are systematically derived and compared with other Negative Emission Technologies (NET). These include the high concentration and purity of the CO2 to be captured compared to Direct Air Carbon Capture (DAC) and Post-combustion Carbon Capture (PCC) as well as the emission-free use of hydrogen resulting in a higher possible CO2 capture rate compared to hydrocarbon-based biofuels generated with Bioenergy with Carbon Capture and Storage (BECCS) technologies. Further, the role of carbon-negative hydrogen in future energy systems is analyzed, taking into account key societal and technological drivers against the background of climate adaptation and mitigation. For this purpose, taking the example of the Federal Republic of Germany, the ecological impacts are estimated, and an economic assessment is made. For the production and use of carbon-negative hydrogen, a saving potential of 8.49–17.06 MtCO2,eq/a is estimated for the year 2030 in Germany. The production costs for carbon-negative hydrogen would have to be below 4.30 € per kg in a worst-case scenario and below 10.44 € in a best-case scenario in order to be competitive in Germany, taking into account hydrogen market forecasts.

Enhancement of dark fermentative H2 production by gas separation membranes: A review

Biohydrogen production via dark fermentation is currently the most developed method considering its practical readiness for scale-up. However, technological issues to be resolved are still identifiable and should be of concern, particularly in terms of internal mass transfer. If sufficient liquid-to-gas H₂ mass transfer rates are not ensured, serious problems associated with the recovery of biohydrogen and consequent inhibition of the process can occur. Therefore, the continuous and effective removal of H₂ gas is required, which can be performed using gas separation membranes. In this review, we aim to analyze the literature experiences and knowledge regarding mass transfer enhancement approaches and show how membranes may contribute to this task by simultaneously processing the internal (headspace) gas, consisting mainly of H₂ and CO₂. Promising strategies related to biogas recirculation and integrated schemes using membranes will be presented and discussed to detect potential future research directions for improving biohydrogen technology.

A review of the innovative gas separation membrane bioreactor with mechanisms for integrated production and purification of biohydrogen

This review article focuses on an assessment of the innovative Gas Separation Membrane Bioreactor (GS-MBR), which is an emerging technology because of its potential for in-situ biohydrogen production and separation. The GS-MBR, as a special membrane bioreactor, enriches CO₂ directly from the headspace of the anaerobic H₂ fermentation process. CO₂ can be fed as a substrate to auxiliary photo-bioreactors to grow microalgae as a promising raw material for biocatalyzed, dark fermentative H₂-evolution. Overall, these features make the GS-MBR worthy of study. To the best of the authors' knowledge, the GS-MBR has not been studied in detail to date; hence, a comprehensive review of this topic will be useful to the scientific community.

Improvement of methane content in a hydrogenotrophic anaerobic digester via the proper operation of membrane module integrated into an external-loop

This work assessed the feasibility of a hydrogenotrophic biogas process integrated with a membrane module in the external-loop design. The major scope was to conduct the investigation from the perspective of the membrane unit and reveal how the operating strategy influences the efficiency of biogas formation. It was observed that the fermenter worked with an improved efficacy, indicated by the higher concentration of methane in the headspace (80-90%) when the gas loading intensity, defined as the ratio of inlet gas permeation rate and the circulation rate of the liquid phase, was adjusted to lower values (3-5.3×10^-3). Such results are implying that the mass transfer of H₂ into the reactor is dependent on this critical parameter. Moreover, attention should be paid to the fouling of the module under longer-term experiments to keep its performance at a sufficient level.