NextGenBiogas – Flexible production of bioenergy can contribute stability for power grids

Demand-driven biogas production as a contribution to the energy transition

If biogas is to play an integral part in any future energy system, it is vital to find ways in which it can be produced on a flexible basis and thereby made available on demand. This will also help secure the viability of biogas as a renewable, biogenic source of energy.

The objective of the NextGenBiogas collaborative research project is to develop a flexible process for the production for biogas on demand for the purposes of flexible power generation. Use of bioengineering methods in a two‑stage process will make it possible to ramp up methane production significantly more quickly than is possible with current technology and research. To achieve this, the anaerobic digestion process must be operated in such a way that the microorganisms involved in methane production can react quickly to changes in operating conditions. Instead of using the substrate or the actual biogas as an energy‑storage medium, the energy is stored in the form of easily convertible organic acids – e.g. acetic acid – which are produced in the first stage of the two‑stage biogas process. In parallel, the microbiome is being characterized by means of next‑generation sequencing.

Biogas facility.
Biogas plants that produce on demand can help provide extra stability for power grids.

The project promises to bring the following benefits: optimization of biogas production, higher process stability, reduction of required gas storage capacity, increased security, and extra stability for the power grid. It will pave the way for a flexible production of bioenergy on demand in order to be able to compensate for fluctuations in power generation from the sun and wind.

Project results

Applied concept

The anaerobic digestion process is a so-called two-stage anaerobic system: in a first, hydrolytic stage, acid formation takes place, and in a subsequent, methanogenic stage, biogas is formed. For running the two-stage system efficiently, the following criteria should be considered: the construction of reactors involved in both stages, the operating conditions, the composition of the inoculum, and the composition of the feeding substrate.

In order to be able to quickly increase methane production in the second stage if required, easily convertible organic acids and alcohols are produced as storage medium in the first hydrolytic stage. The identification of microorganisms with good adaptation properties to changes in system operation for fast and efficient methane production is an important topic within the NextGenBiogas project.

The hydrolytic stage and the methanogenic stage have been tested separately under laboratory conditions.


Efficient acid production in the hydrolytic phase

In the hydrolytic stage, the optimal conditions for fast and efficient acid production have been identified corresponding to the highest potential methane production, which can be obtained when applying this hydrolysate in the methanogenic reactor. The optimal conditions were found under t = 51°C, pH = 5.5, the addition of organic dry residues in the amount of 30 g. The highest acid formation was achieved at the ratio of shredded corn silage to cattle slurry of 50:50 in the substrate input.

Methanogenic stage of anaerobic biogas installation with fixed-bed circulation reactor.
© Fraunhofer IGB
Methanogenic stage of anaerobic biogas installation with fixed-bed circulation reactor.

Flexible and demand-oriented biogas production in the methanogenic phase

In the methanogenic stage, different scenarios of flexible feeding have been tested, aiming at the fastest microorganisms’ recovery and the highest biogas production efficiency after selected starvation phases. The synthetic medium corresponding to the hydrolysate from the first stage is used as a feed substrate.


Metagenome- and metatranscriptome analyses with short reads sequencing, Krona software and “Kraken 2” method.
© Fraunhofer IGB
Metagenome- and metatranscriptome analyses with short reads sequencing, Krona software and “Kraken 2” method.

Process monitoring and regulation through microbial approach

Alongside monitoring and evaluating the experimental trials, metagenome and metatranscriptome analyses of the inoculum and the samples from the two-stage system are carried out [1–3]. Based on the acquired microbial data, we were able to both classify the species involved in each case and determine their relative abundance. This information enables us to map the microorganisms involved in the fermentation process. By conducting the metagenome and metatranscriptome analysis, the microorganisms’ behavior in response to the experimental changes will be identified and assessed. This enables targeted inoculation of the process with these microorganisms, and in addition, the search for the optimal grow conditions could be streamlined.


The ongoing lab-scale experiments are aimed at optimizing biogas production in the methanogenic phase, which is carried out in a fixed-bed circulating reactor. The obtained results are of the most interest for designing and operating a two-stage anaerobic system for biogas production in full-scale.


[1] Grohmann, A., Fehrmann, S., Vainshtein, Ye. et al. Microbiome dynamics and adaptation of expression signatures during methane production failure and process recovery, Bioresource Technology 247 (2018).

[2] Grohmann, A., Vainshtein, Y., Euchner, E. et al. Genetic repertoires of anaerobic microbiomes driving generation of biogas. Biotechnol Biofuels 11, 255 (2018).

[3] Wood DE, Lu J, Langmead B. Improved metagenomic analysis with Kraken 2 (2019). Genome Biology. 2019 Nov; p. 76230.

Project information

Project title

NextGenBiogas – Flexible production of bioenergy can contribute stability for power grids


Project duration

February 2019 – March 2022


Project partners

  • Hochschule Hamm-Lippstadt, Hamm (Coordination)
  • Fraunhofer IGB, Stuttgart


We would like to thank the German Federal Ministry of Food, Agriculture and Consumer Protection (BMELV) and the Agency for Renewable Resources (FNR) for funding the project "NextGenBiogas", promotional reference 22408818.


Federal Ministry of Food and Agriculture.