Past projects

The micro­bio­lo­gical risks associated with the propor­tional injection of hydrogen and biome­thane into the natural gas grid can be estimated to a certain extent on the basis of data that has already been published. Since hydrogen is an energy source for numerous anaerobic metabolic processes, there is a considerable risk potential for under­ground storage facilities, especially pore storage facilities. Many German storage facilities offer the necessary condi­tions for rapid and complete microbial degra­dation of hydrogen intro­duced into the system, which is why it is not possible to specify a safe lower concen­tration limit for hydrogen.

The rapid utili­sation of hydrogen by sulphate-reducing and metha­no­genic proka­ryotes can have signi­ficant technical and economic conse­quences, such as sulphide formation (H₂S), micro­bially induced corrosion (MIC) or reduced permea­bility in the storage rock. At present, we can only speculate about the possible extent of negative effects and whether certain storage sites with lower risk exist.

Supported by the state of Saxony-Anhalt, a three-year research programme analysed the assessment criteria for the safe under­ground storage of renewable hydrogen and developed a method for monitoring the safety of under­ground storage facilities. This catalogue of methods covers all the analyses necessary for a practical micro­bio­lo­gical storage assessment. It also outlines ways of dealing with micro­bially induced disturbances.

To evaluate the analysis methods, a culture collection of micro­or­ga­nisms from German under­ground storage facilities was created, which grow under different condi­tions. Using these cultures, the influence of micro­or­ga­nisms on hydrogen storage under the different ecolo­gical condi­tions of cavern and pore storage facilities was simulated and the necessary accom­panying analyses were defined. The results of these model tests made it possible to determine the key risk parameters for hydrogen storage in under­ground storage facilities.

Possible strategies for preventing and combating microbial popula­tions in storage facilities were tested and evaluated under practical condi­tions in high-pressure tests. The storage monitoring process was incor­po­rated into MicroPro GmbH’s service portfolio.

As part of a research colla­bo­ration, silages were produced from different plant parts that were considered parti­cu­larly suitable for the production of biogas due to their increased acetate and reduced lactate content.

The increased acetate production was induced by inocu­lating the plant material with bacterial strains from different physio­lo­gical groups. In parti­cular, the addition of heter­o­fer­men­tative lactic acid bacteria triggered a signi­ficant increase in acetate formation in the ensiled material. The special test silages produced in this way were then fed into biogas production by the research partners. The biogas production was examined quali­ta­tively and quanti­ta­tively in order to determine differences.

The compe­ti­ti­veness of the test strains used for ensiling varies greatly and represents a signi­ficant challenge for the process. It was confirmed that the fermen­tation acid patterns and the specific methane yields of the plant samples could be signi­fi­cantly influenced by the addition of biolo­gical ensiling agents. The principle of fermen­tation product control was clearly confirmed in this project phase. Further work will focus on the selection and compo­sition of a suitable micro­or­ganism consortium for biogas-oriented ensiling.

In many years of research, MicroPro GmbH has succeeded in isolating special hydrocarbon-degrading bacteria (including Gordonia) from natural sites, which do not develop in the aqueous phase — as is usually the case — but directly in the oil phase. In a water-oil emulsion, these bacteria penetrate oil droplets and develop into masses. The oil is strongly emulsified and rapidly degraded by the formation of surface-active substances. Special areas of appli­cation are aquatic systems (e.g. lakes, rivers, seas) and shore zones with corre­sponding oil conta­mi­nation. When these special bacterial cultures are intro­duced into a water-oil mixture, the bacteria pass directly into the oil phase (conta­mi­nation) and are therefore not diluted by the water.

Hemp is a natural product that is degraded under favorable condi­tions by a broad spectrum of micro­or­ga­nisms. There is no infor­mation in the literature on the stabi­lization of hemp products by biocides or on the use of hemp waste and recycling material for the production of bioenergy sources in the form of hydrogen and methane.

By applying methods for the deter­mi­nation of bacte­rio­static and biocidal efficacy, 3 biocides could be selected from more than 20 pre-selected products due to their high efficacy against complex germ mixtures. In long-term storage tests with repeated inocu­la­tions, stabi­lization was achieved both for hemp fibre materials and for surfac­tants made from hemp oil.

The microbial degra­dation of hemp fibers was inves­ti­gated in detail. Previously undescribed struc­tures of the union of elementary fibers into fiber bundles were detected. Special bacterial cultures for the degra­dation of pectin, anaerobic fermen­tation, cellulose decom­posers and methane formers were isolated. The basis for the conception of a new, biotech­no­lo­gical process of fiber disin­te­gration was created, which will be trans­ferred to the BMBF project 03|1522.

The biogas production (methane) from waste materials and hemp fibers was deter­mined on a laboratory scale with yields of 300 to 450 m³/t. A novel two-stage process of alcoholic fermen­tation with subse­quent biogas production was developed for hemp. This made it possible to produce 80 m³ of hydrogen and 130 m³ of methane per ton of hemp dust.