Episode 35 of the WHySE Creatures Stories
This post first appeared on LinkedIn on 29 September 2026.
“Hydrogen from the wastewater treatment plant? But we don’t have any water electrolysis,” asks Monkey.
Dog shakes his head. “You don’t need it either.”
Rat frowns. “How’s that supposed to work?” “A wastewater treatment plant has two material streams that have hardly been considered as sources of material until now,” says Dog. “Sewage sludge and sewage gas.”
Pig pricks up his ears. “Sewage gas? I’ve only ever heard of that in relation to combined heat and power plants. That’s where it’s used to generate electricity and heat.” “That’s exactly where it starts,” says Dog. “Sewage gas consists largely of methane. With methane pyrolysis – a process that splits methane into hydrogen and solid carbon – hydrogen is produced without any CO₂ escaping. And the carbon could be put to other uses.”
Rat thinks for a moment. “And the sewage sludge?” “That’s going to be mandatory for large-scale plants anyway,” says Dog. “The Sewage Sludge Ordinance requires phosphorus recovery from 2029 onwards. Many people think of mono-incineration when they hear that. However, if you pyrolyse the sludge or gasify it and treat it further, you get not only phosphorus but also a hydrogen-rich gas.”
Rat puts the tablet aside. “So the wastewater treatment plant is more than just a place where wastewater is cleaned. It’s a source of energy, materials and water.” Dog nods. “Exactly. Every wastewater treatment plant should now be asking itself whether there are any more treasures to be found besides clean water.”
My task at this stage is to prioritise the sequence of questions before the first plant is planned or an existing plant is expanded. This is because sewage gas, sewage sludge and water electrolysis each follow their own set of rules – in terms of planning permission, customer structure and operational procedures.
Anyone who only tackles the phosphorus recovery requirement shortly before the deadline risks facing time pressure when it comes to planning permission and plant design. Anyone wishing to consider hydrogen production in parallel needs clarity on material flows and operating procedures at an early stage – not just when the deadline is looming.