Green hydrogen is produced by using renewable electricity to split water molecules into H2 and oxygen inside machines called electrolysers. But in most cases, the oxygen is not required and is simply vented into the atmosphere.

However, oxygen is a valuable gas that is not only required for medical purposes, but is also used in the steel, chemicals, pharmaceutical, oil, paper and aquaculture industries. So why throw away the O2 when it could instead be sold — generating additional revenue for green H2 producers?

Danish green hydrogen supplier Everfuel has today answered that question, revealing that it has signed a conditional long-term agreement to sell the by-product oxygen from its planned 300MW HySynergy 2.0 green hydrogen project in Fredericia, Denmark, to an undisclosed buyer.

That project was recently awarded DKr246.3m ($35m) from the Danish government for its first 100MW phase.

“The agreement is conditional on final investment decision by the undisclosed partner for the construction of a process facility adjacent to HySynergy which will use the oxygen, and Everfuel’s decision to progress HySynergy 2.0,” the Danish company said in a statement.

“The long-term contract includes payment for a capacity reservation of oxygen and a recurring payment for the oxygen supply. Everfuel expects a minimum revenue of €1m [$1.05m] per year once the agreement is fully implemented, with no expected additional cost to Everfuel.”

In June, Everfuel announced a long-term agreement with oil refiner Crossbridge Energy to supply hydrogen from HySynergy 2.0 for use at the latter’s refinery in Fredericia.

Everfuel also plans to sell waste heat from the project.

The company announced last month that the first hydrogen had been produced at its 20MW HySynergy 1.0 facility, which is at the same location as the planned SySynergy 2.0 project. Waste heat from that project — currently Europe’s joint-largest green H2 facility — is being sold to local district heating operator TVIS.

Synergy 2.0 is due to built in three 100MW phases, each producing up to 40 tonnes of green hydrogen per day, with completion planned for 2025.