The energy transition currently has two major efficiency problems: First, surplus electricity from renewable sources is often curtailed. Second, valuable energy potentials from biowaste often remain unused. This is precisely where a project of the North German Real-World Laboratory (NRL) at the Bützberg biogas and composting plant comes in. It shows how combining both areas can develop a new approach for climate-friendly gas supply.
Marcel Schröder („Stadtreinigung Hamburg“, City Cleaning) and M.Sc. She Ming Ng (Hamburg University of Technology) have published a white paper on this. At the center is a power-to-gas approach that has hardly been tested on an industrial scale in this form: biological in-situ methanation in a dry fermentation plant (see H2Int. No. 4-2025).
Hydrogen produced by electrolysis from renewable electricity is introduced directly into the fermentation process. Microorganisms – so-called hydrogenotrophic archaea – convert the CO2 contained in the biogas together with the hydrogen into additional methane.
Technically, the concept is based on a 1 MW PEM electrolyzer that responds flexibly to low electricity prices and thus specifically uses surplus electricity. The hydrogen produced is either fed directly into the fermenters or temporarily stored in a repurposed pipeline section – a comparatively simple and cost-effective solution.
The goal: increase methane yield while improving gas quality. Conventional raw biogas typically consists of only about 60 percent methane, with the remainder predominantly CO2. Through additional methanation, this CO2 content is reduced – a decisive advantage for feeding into the natural gas grid.
While in-situ biomethanation has primarily been investigated in the laboratory so far, the step into practice succeeded in Bützberg. First, laboratory tests at Hamburg University of Technology confirmed the fundamental feasibility under dry, discontinuous conditions – a previously little-researched field.
In subsequent preliminary tests on an industrial scale, hydrogen was initially fed from compressed gas cylinders. The measurement results clearly show: During hydrogen addition, the CO2 concentration in the biogas decreased while the methane content increased – direct evidence of biological methanation in ongoing operation.
In parallel, the plant could be technically upgraded to handle hydrogen. So-called “H2 readiness” includes not only new piping infrastructure but also adapted measurement technology and safety concepts.
The greatest challenge lay not so much in the hardware, but primarily in process control and sensor technology, which must meet particularly high requirements in research operations.
The results are promising: The project shows that existing biogas plants can be expanded relatively easily technically and thus become flexible energy storage systems. Given around 10,000 biogas plants in Germany, this opens up considerable scaling potential.
At the same time, the economic outlook currently remains limited. High electricity costs for electrolysis and comparatively low revenues for biomethane currently prevent profitable operation. According to project information, electricity prices would have to be significantly below today’s level to achieve economic viability.
Regulatory framework conditions also slow development. Instruments such as the EnWG (German Energy Industry Act) model “Use Instead of Curtail” could help, but are not yet applied comprehensively. Despite these challenges, the project provides important evidence: Coupling the electricity, gas, and waste sectors can work – even in existing infrastructure.
In addition to improved use of renewable energies, the concept helps to utilize CO2 streams meaningfully and integrate gas networks as energy storage. For the biogas industry, this represents a new perspective. Instead of pure electricity production, plants could increasingly act as flexible methane producers in the future – especially when political framework conditions and market mechanisms are adjusted accordingly.
The North German Real-World Laboratory sees itself as a blueprint. The upcoming project phases, in which H2supply is extended to multiple fermenters and automated, should show whether the results can be stably reproduced. One thing is already clear: Green hydrogen as a booster for biomethane is more than a theoretical concept. In Bützberg, it is becoming industrial reality – with the potential to become an important pillar of the future hydrogen economy.
