Biogas and renewable electricity are powerful on their own. Together, they are even stronger. In Sønderborg, Power-to-Gas demonstrates how we can unlock even more energy from our unavoidable organic residues.
3
1
32
More gas from the same organic residues
The biogas plant in Glansager is anything but ordinary.
Here, green electricity from wind and solar is used to boost biogas production, delivering more methane from the very same amount of feedstock.
By mixing biogas with hydrogen produced through electrolysis, the process significantly increases the methane production.
In doing so, the solution links the electricity and gas systems and adds extra momentum to the shift away from fossil gas.
The magic happens in the world’s first grid-connected Power-to-Gas plant, but the technology is far from hocus-pocus. In fact, it demonstrates the potential to be replicated at biogas facilities around the world.
Behind the results
Chemistry and climate
Biogas is a key part of the energy system in Sønderborg, especially in sectors where electrification is difficult. The art lies in getting the most out of the unavoidable waste from households, agriculture and the food industry.
That is exactly what happens in Glansager. Here, the biogas plant works hand in hand with the world’s first Power-to-Gas system to use resources far more efficiently.
The process spans three facilities: a biogas plant, an electrolysis unit, and a methanation unit.
In the biogas plant, bacteria break down residual products and produce methane and CO₂. In the electrolysis unit, electricity splits water into hydrogen and oxygen.
Then, in the methanation unit, hydrogen reacts with CO₂ from the biogas and is converted into additional methane. As a result, the composition shifts to roughly 90 % methane and 10 % CO₂.
This increases the energy yield from residues, sending more gas to companies with energy-intensive needs, such as heavy industry and shipping.
Linking electricity and gas
Wind and solar deliver energy when the weather allows it, not necessarily when demand is highest.
That creates periods of both shortage and surplus. As a result, wind turbines sometimes stand still even when it is windy: quite simply because we are producing more electricity than we can use.
This is where Power-to-Gas proves its value by making surplus electricity useful.
The plant can be switched on and off as needed, capturing power that would otherwise go to waste. In other words, green electricity becomes green gas.
That eases pressure on the power grid and makes it easier to integrate large amounts of wind and solar by giving the energy system a buffer.
Glansager is therefore more than a local facility. It is an active part of the region’s integrated energy system – and a model for how other cities can get more value from renewable energy while strengthening supply security, even when the weather changes.
Self-sufficient Sønderborg
Potato peels, coffee grounds, and manure have something in common.
They can all become energy in a biogas plant.
In Sønderborg, the biogas system has matured to the point where the area can cover its gas demand with locally produced gas.
Two biogas plants in Kværs and the facility in Glansager together produce enough biogas each year to match virtually all of the Sønderborg area’s annual gas consumption.
The Power-to-Gas add-on in Glansager is the cherry on top: by enriching the biogas with hydrogen, the same feedstock delivers more and the whole energy system becomes more flexible.
Energy storage is a central challenge in the global green transition. With Power-to-Gas, Sønderborg has found a way to “bottle the energy” – a method that displaces fossil fuels, strengthens local energy security, and gives value to local farmers.