Arne Seifert

Essential prerequisites for successful bioprocess development of biological CH4 production from CO2 and H2

Abstract The production and storage of energy from renewable resources steadily increases in importance. One opportunity is to utilize carbon dioxide (CO2)-type hydrogenotrophic methanogens, which are an intriguing group of microorganisms from the domain Archaea, for conversion of hydrogen and CO2 to methane (CH4). This review summarizes the current state of the art of bioprocess development for biological CH4 production (BMP) from pure cultures with pure gasses. The prerequisites for successful quantification of BMP by using closed batch, as well as fed-batch and chemostat culture cultivation, are presented. This review shows that BMP is currently a much underexplored field of bioprocess development, which mainly focuses on the application of continuously stirred tank reactors. However, some promising alternatives, such as membrane reactors have already been adapted for BMP. Moreover, industrial-based scale-up of BMP to pilot scale and larger has not been conducted. Most crucial parameters have been found to be those, which influence gas-limitation fundamentals, or parameters that contribute to the complex effects that arise during medium development for scale-up of BMP bioprocesses, highly stressing the importance of holistic BMP quantification by the application of well-defined physiological parameters. The much underexplored number of different genera, which is mainly limited to Methanothermobacter spp., offers the possibility of additional scientific and bioprocess development endeavors for the investigation of BMP. This indicates the large potential for future bioprocess development considering the possible application of bioprocessing technological aspects for renewable energy storage and power generation.

Method for assessing the impact of emission gasses on physiology and productivity in biological methanogenesis

This contribution presents a method for quantification of the impact of emission gasses on the methane production with hydrogenotrophic methanogenic archaea. The developed method allows a robust quantification of the influence of real gasses on the volumetric productivity of methanogenic cultures by uncoupling physiological and mass transfer effects. This is achieved over reference experiments with pure H2 and CO2, simulating the mass transfer influence of the non-convertible side components by addition of N2 to the reactant stream. Furthermore, this method was used to examine the performance of Methanothermobacter marburgensis on different emission gasses. None of the present side components had a negative effect on the volumetric methane production rate. The presented method showed to be ready to use as a generic tool for feasibility studies and quantification of the physiological impact regarding the use of exhaust gasses as reactant gas for the biological methanogenesis.

Biological methane production under putative Enceladus-like conditions.

The detection of silica-rich dust particles, as an indication for ongoing hydrothermal activity, and the presence of water and organic molecules in the plume of Enceladus, have made Saturn’s icy moon a hot spot in the search for potential extraterrestrial life. Methanogenic archaea are among the organisms that could potentially thrive under the predicted conditions on Enceladus, considering that both molecular hydrogen (H2) and methane (CH4) have been detected in the plume. Here we show that a methanogenic archaeon, Methanothermococcus okinawensis, can produce CH4 under physicochemical conditions extrapolated for Enceladus. Up to 72% carbon dioxide to CH4 conversion is reached at 50 bar in the presence of potential inhibitors. Furthermore, kinetic and thermodynamic computations of low-temperature serpentinization indicate that there may be sufficient H2 gas production to serve as a substrate for CH4 production on Enceladus. We conclude that some of the CH4 detected in the plume of Enceladus might, in principle, be produced by methanogens.Many methanogenic archaea use H2 and CO2 to produce methane. Here, Taubner et al. show that Methanothermococcus okinawensis produces methane under conditions extrapolated for Saturn’s icy moon, Enceladus, and estimate that serpentinization may produce sufficient H2 for biological methane production.

Biomethanisierung — ein Prozess zur Ermöglichung der Energiewende?

Biomethanation is a biotechnological process for the production of methane from hydrogen and carbon dioxide, utilizing an archaeal group of microorganisms referred to as methanogens. Biomethanation can be performed by using pure and industrial emission waste gases in a continuous but also in discontinuous bioprocess mode. Volumetric methane productivity as high as 950 millimoles CH4 per litre and hour was achieved. Optimization of methane production regarding quality and quantity of methane is currently being examined.