Green Hydrogen Meets Wastewater Treatment: Electrolysis By-Product Oxygen Comes Online
A New Meeting Point for the Energy and Water Sectors
Green hydrogen production happens through water electrolysis, with high-purity oxygen released as a by-product. Wastewater plants, in turn, spend more than half of their energy consumption on aeration in biological tanks. New project models integrating these two processes are spreading rapidly in Europe.
Simultaneous Gain for Both Sectors
In integrated project models:
- The hydrogen producer pipes oxygen to the wastewater plant instead of releasing it to the atmosphere, generating additional revenue
- The wastewater plant takes pure oxygen directly instead of compressing atmospheric air, cutting energy consumption by 20–30 percent
- Higher mass oxygen transfer in the same tank lifts process capacity
- Net carbon footprint is lowered for both sectors
First Full-Scale Examples
Oxygen pipeline projects between port wastewater plants and adjacent green hydrogen facilities have gone live in the Hamburg port area in Germany and the Rotterdam port area in the Netherlands. Despite total investment cost coming in 12 percent higher than a conventional standalone design, a 7-year payback period is being reported.
Technical Design Considerations
Technical considerations for integration:
- Foam and excess dissolved oxygen management when using pure oxygen
- The economic limit of pipeline length (typically below 2 km)
- Backup air support system (when hydrogen production stops)
- Plant scale matching (flow-capacity alignment)
- Synchronising the contractual hydrogen production schedule with aeration demand
The Carbon Angle
Debate around the carbon footprint of green hydrogen production continues, given its high electricity consumption. Integration with the wastewater sector concretises the by-product value of electrolysis and contributes to economic feasibility. Under the EU Renewable Energy Directive (RED III), by-product revenue is recognised as supporting evidence in green hydrogen production certification.
Potential in Turkey
Turkey's green hydrogen roadmap was published in 2024, with a 5 GW electrolysis capacity target by 2035. That capacity corresponds to an annual oxygen production of around 600,000 tonnes, which would cover roughly one-third of the oxygen demand of Turkey's large urban wastewater plants. Mersin, İskenderun and İzmir, identified as hydrogen valleys, offer natural opportunities for integrated planning.
Investment Model
The recommended contractual structure for integrated projects has the wastewater operator committing to long-term (15–20 year) fixed-price oxygen offtake while the hydrogen producer secures an additional revenue stream. This structure also lends itself well to public-private partnership models.
Market Outlook
A European Water Sector Federation report projects that the number of integrated green hydrogen and wastewater projects in Europe will exceed 50 by 2030. For Turkey, the market opportunity offers a critical medium-term revenue-cost optimisation tool for both green hydrogen investors and wastewater operators.