Oxygen Electrolysis: Turning a Byproduct into a Powerful Strategic Asset 

Key Takeaways 

• Oxygen from electrolysis produces oxygen in large volumes, up to 8 kg of O₂ per kg of hydrogen  

• Oxygen from electrolysis is often released into atmosphere, despite industrial value  

• Oxygen is used in several industrial processes, such as steel and chemicals manufacturing  

• Oxygen from electrolysis supports water treatment and aquaculture

• Co-locating hydrogen production with oxygen demand improves project economics  

• Oxygen utilisation during hydrogen production can reduce reliance on air separation units  

• The value of oxygen electrolysis depends on purity, scale, and location

• Stargate Hydrogen supports integrated projects where both H₂ and O₂ are used

Oxygen Electrolysis 

Hydrogen projects are rarely evaluated based on their oxygen output, even though oxygen from electrolysis is produced in far greater mass than hydrogen itself. This imbalance in attention has led to a persistent blind spot in project design. 

For every kilogram of hydrogen generated through water electrolysis, roughly eight kilograms of oxygen are produced. At an industrial scale, this means that any serious hydrogen facility is also a large oxygen production site. Yet in many cases, this oxygen is simply released into atmosphere. 

This approach is not due to a lack of applications. It is a result of how projects are structured. Hydrogen is treated as the main product, while oxygen is treated as an unavoidable side stream. That assumption limits both technical performance and financial outcomes. 

A more effective approach is to treat electrolysis as a dual-output process from the start. When oxygen utilisation during hydrogen production is considered early, the system begins to look very different. Infrastructure decisions change, partnerships shift, and new value streams become viable. 

What Makes Oxygen Sourced from Water Electrolysis Special 

Oxygen can be produced in several ways, but electrolysis offers a distinct profile. Unlike traditional air separation, oxygen from electrolysis is generated continuously and directly at the point of hydrogen production. 

The underlying reaction is straightforward: 

2H₂O → 2H₂ + O₂ 

What matters in practice is not the chemistry itself, but the implications of scale and purity. Oxygen obtained through electrolysis is typically high purity, often exceeding 95 percent without additional processing. This makes it suitable for a wide range of industrial uses. 

Another defining characteristic is that oxygen production is locked to hydrogen output. This creates both constraints and opportunities. On one hand, oxygen supply cannot be adjusted independently. On the other hand, it provides a predictable and steady stream that can support continuous industrial processes. 

This combination of purity, consistency, and on-site availability positions oxygen from electrolysis as more than just a byproduct. It is a ready-to-use input for multiple sectors. 

Comparing Pure Oxygen Production Pathways 

To understand the role of oxygen electrolysis, it helps to compare it with conventional supply methods. Most industries rely on cryogenic air separation units, which are designed specifically to produce oxygen, nitrogen, and argon. 

The difference is not just technical; it is structural. Air separation requires dedicated capital investment, separate energy input, and its own operational footprint. Electrolysis, in contrast, produces oxygen as part of hydrogen generation with no extra costs. 

This comparison shows that oxygen obtained through electrolysis is not about replacing air separation everywhere. It is about identifying situations where co-production creates an advantage. That advantage becomes clear when oxygen demand exists close to the electrolyser. 

Industrial Applications of Oxygen  

Large industrial processes consume oxygen in volumes that align well with electrolysis output. Steelmaking is the clearest example. Oxygen is injected into molten iron to remove carbon and impurities, forming the basis of modern steel production. 

As hydrogen-based steelmaking gains traction, the relationship between hydrogen and oxygen becomes more direct. Hydrogen is used to reduce iron ore, while oxygen supports downstream refining processes. When both gases are produced on-site, the system becomes more efficient and less dependent on external supply chains. 

A similar pattern appears in high-temperature industries such as cement and glass manufacturing. These processes benefit from oxy-fuel combustion, where oxygen replaces air to increase flame temperature and reduce nitrogen dilution. The result is a more controlled process with lower emissions and easier carbon capture. 

In these environments, oxygen from electrolysis is not just a substitute supply. It changes how the process is designed and operated. 

Environmental Systems Applications 

In environmental applications, the value of oxygen is closely tied to concentration. Air contains only about 21 percent oxygen, which limits the efficiency of many treatment processes. 

Wastewater treatment is a good example. Aeration systems rely on oxygen to support bacteria that break down organic matter. When air is used, large volumes must be moved through the system, consuming significant energy. 

Replacing air with electrolysis oxygen changes the dynamics of the process. Higher oxygen concentration improves transfer efficiency, reduces reactor size, and allows for more precise control. This can translate into both lower operating costs and higher treatment capacity. 

The same principle applies to advanced water treatment processes such as ozonation. Higher purity oxygen improves ozone generation efficiency, which directly affects treatment performance. 

Energy Systems Applications 

Electrolysis is often part of a larger system, particularly in Power-to-X applications. In these setups, hydrogen is used to produce fuels or chemicals, and oxygen can be reused within the same process. 

Biomass gasification illustrates this well. When air is used, nitrogen dilutes the resulting gas, reducing its quality. Using oxygen instead produces a cleaner syngas with higher energy content. 

This is where oxygen utilisation and hydrogen production become a system-level decision. Instead of treating oxygen as excess, it is routed back into the process to improve performance. 

Carbon capture systems follow similar logic. Oxy combustion produces exhaust streams with high CO₂ concentration, simplifying capture. Electrolysis generated oxygen supports this without requiring added air separation infrastructure. 

Chemical and High-Purity Oxygen Applications 

The chemical industry depends on controlled reactions where oxygen purity directly affects outcomes. Processes such as ethylene oxide production and partial oxidation of hydrocarbons rely on stable and predictable oxygen input. 

Oxygen from water electrolysis meets these requirements in many cases without additional purification. This reduces complexity and improves consistency. 

At the highest purity levels, oxygen can also be used in medical applications. While this requires strict standards, electrolysis systems can be designed to meet them.  

The Economics of Oxygen Valorization Electrolysis 

Despite its potential, oxygen is still frequently underutilised. The main reason is not technical, but economic alignment. 

Oxygen is difficult to transport over long distances. Compression and liquefaction add cost. This makes local use essential. 

The value of oxygen byproduct electrolysis therefore depends on proximity. When demand exists near the electrolyser, oxygen can replace purchased supplies or enable more efficient processes. When demand is absent, it is often vented. 

This creates a clear design principle. Hydrogen projects should be located and structured around both hydrogen and oxygen demand. When this is done well, the economics of the entire system improves. 

In regions such as Europe, this alignment is already visible. Green steel projects, wastewater treatment upgrades, and aquaculture operations are strong demand centers for oxygen from electrolysis. 

From Oxygen as a Byproduct to System Driver 

The perception of oxygen as a wasted output can create limitations in current hydrogen project design. If that perception changes, new opportunities will appear. 

Instead of asking how to dispose of oxygen, the question becomes how to use it effectively. This shift leads to: 

• Different site selection decisions  

• New industrial partnerships  

• Integrated infrastructure planning  

Oxygen valorisation electrolysis is not an add-on. It is part of building efficient, economically viable hydrogen systems. 

How Stargate Hydrogen Supports This Approach 

Stargate Hydrogen develops Alkaline electrolysis systems with real industrial integration in mind. This includes not only hydrogen production but if requested by clients, their engineering teams can ensure the effective use of oxygen from electrolysis. 

By focusing on system-level performance, Stargate Hydrogen can support projects where: 

• Oxygen demand is identified early  

• Both gas streams are utilised  

• Infrastructure is designed for dual outputs  

This approach helps turn oxygen from water electrolysis into a usable and valuable resource rather than a wasted stream. 

Next Steps: Designing for Both Outputs 

Projects that account for oxygen from the beginning can achieve better efficiency, stronger economics, and lower emissions. This requires coordination across industries and a willingness to rethink traditional project boundaries. 

Get in touch with Stargate Hydrogen to explore how your electrolysis system can be configured to make full use of both hydrogen and oxygen streams, based on your specific operational requirements.