Case
Bio-based circular solutions
Biogas
Biosolutions
+6
ProjectZero is Sønderborg’s cross-sector climate partnership, uniting citizens, businesses, utilities and the municipality to achieve a CO₂-neutral energy system by 2029 - and to serve as a living blueprint for cities around the world.
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Decarbonising energy systems requires solutions tailored to local conditions. While electrification is the preferred option for many applications, sectors such as high-temperature industrial processes still require renewable gaseous fuels. At the same time, agriculture produces large volumes of manure and organic residues that release methane if left untreated, contributing to greenhouse gas emissions.
The challenge is therefore twofold: reducing emissions from agricultural waste while providing renewable energy for sectors where direct electrification is not yet feasible.
Meet Martin, a local farmer behind the biogas.
In Sønderborg, agricultural residues have become the foundation of a circular energy system. Manure, food waste and other organic by-products are converted into biogas through anaerobic digestion, capturing methane that would otherwise be released into the atmosphere.
The renewable gas is upgraded and injected into the gas grid, replacing fossil natural gas, while the nutrient-rich digestate is returned to farmland as fertiliser, closing the resource loop.
The region has developed an integrated biogas ecosystem combining large-scale production with farm-based facilities. Local farmers produce renewable energy directly from their own resources, supplying electricity, heat or gas depending on local needs.
Sønderborg is also home to the world’s first Power-to-Gas facility integrated with a biogas plant. By using surplus electricity from wind and solar power to produce hydrogen, the plant converts captured CO₂ into additional methane, increasing renewable gas production while helping balance the electricity system.
Denmark is among Europe’s biogas frontrunners, and Sønderborg has gone even further: the area produces enough biogas to meet the area’s entire annual gas demand.
Sønderborg has become fully self-sufficient in renewable gas, with three biogas plants producing enough biomethane to cover the region’s total gas consumption.
The integrated approach delivers multiple benefits:
Biogas connects rural and urban communities and demonstrates how the green transition can be built on local resources and cooperation.
