Sonderborg – The future zero carbon city


The 76,000 citizens of the little-known Danish municipality Sonderborg act, while politicians talk and climate change is accelerating. They share the vision of ProjectZero and have committed themselves to make Sonderborg zero carbon by 2029.

Sonderborg is a picturesque municipality close to the water and the German border, and it wants to prove that climate neutrality is achievable when cities take decisive action and ensure citizens and companies participate in finding new solutions and retrofitting society’s energy consumption and generation.

The ProjectZero visionary project is focused on transitioning Sonderborg into a ZERO carbon community, based on sustainable growth and creating new green jobs. Energy efficiency and energy from the area’s own renewable sources are the key means to turn the vision into reality. New thinking is essential and public policy and investments fuel the transition.

In SmartEnCity, Sonderborg seeks to

  • Demonstrate ambitious electrification of Sonderborg’s Roadmap2020 and Roadmap2015, including integration of rooftop PV power production
  • Integrate local green transit mobility solutions
  • Energy retrofitting existing housing association buildings in close cooperation with tenants
  • Engage the citizens as co-designers of the Smart Zero Carbon Sonderborg ambition based integrated solutions, comprehensive learning and the introduction of new ICT based energy information.

Renewable energy in the city

Sonderborg town is supplied with district heating from the Sonderborg District Heating company. The company has a mix of heating sources, including waste incineration, geothermal, solar and biomass, and natural gas for peak loads. Waste incineration is only counted as 50% renewable according to national standards, otherwise the city is mainly heated through renewables. There are five district heating companies supplying heat to the Sonderborg Municipality outside of the town, all with varying degrees of RES. Among these heating sources are solar, heat pump, gas turbine, immersion heater, and a planned straw-fired boiler that will be operational in 2019.

Sonderborg Municipality produced 47GHh electricity from RES in 2016, which is 6 GWh less compared to 2015 mainly because of less wind. The goal for the Sonderborg area is to become CO2 neutral by 2029, which is planned in combination of reducing CO2 emissions by 50% compared to 2007 levels and covering the remaining consumption with 100% RES. Several larger companies along with private households have installed PV panels to cover their own electricity consumption, selling any surplus production to the grid.

Main Results

- Roadmap2025, an integrated energy planning process to remove 392,000 ton CO2

- Energy retrofit of 815 apartments in 7 departments.

  • Façade insulation, new windows, new ventilation systems, heating automatic,
  • LED, PV roof integrated panels
  • Additional 1,639 apartments with PV/battery systems
  • New ESCO finance schemes demonstrated
  • Online (CIOP) monitoring system

- Residents’ acceptance of investments

- Mobility: 44 biogas busses an investment decision made by Sonderborg Municipality and Sydtrafik (2017)

  • Catalyzing Construction of two gas charging stations in cooperation with Nature Energy
  • Enabling two biogas plants (in operation by 2020, 2022)
  • Enabling Sonderborg to become a pioneer in separation of waste fragments (Sonfor, 2020)
  • Catalyzing the decision of 5 new e and 5 new gas utility
  • waste collection trucks (Sonfor, 2020)
  • Circular economy strategy for Sonfor (2020)
  • Citizen engagement in waste management

- Mobililty: 24 e-mobility charging points established - now a catalyzer for e-mobility

- ICT: A City Information Open Platform (CIOP) implemented as a replication of Tartu/Telia solution with 966 connected data devices and 110 GB total amount of data generated including:

  • digital landing-page for citizens
  • Energy- manager concet
  • New (2022) dynamic data collection from
  • District heating plants, biogas production
  • Local schools
  • Private households
  • Traffic data
  • PV & Wind turbine production

Smart Solutions for Sonderborg

  • Retrofitting
    In Sonderborg, a total of 7 social housing departments will be fully retrofitted to reduce energy consumption, improve indoor climate and support Sonderborg in becoming a carbon-neutral city in 2029.  
  • Solar cells with battery storage in housing associations
    The combination of solar cell plants with a battery storage solution forms a reasonable alternative to feeding the produced electricity into the public grid.
  • New biogas buses and biogas filling stations
    As a zero-carbon mobility solution, 44 new energy-efficient buses fueled by biogas; improved digital services notifying users of departures etc. on apps and displays at major hubs; each of the new buses can carry 4 bikes on board, allowing a combined trip.
  • Public electrical vehicle charging points
    In total 31 EV chargers  have been installed in the Sonderborg area. The implementation of public electrical vehicle chargers not only increases the available infrastructure but also serves as a awareness raising point in the city.
  • Sonderborg ICT Platform 
    Sonderborg's long term vision is to build a Digital Ecosystem for city data and services by integrating various data inputs and sensor systems together into one City ICT Platform, where anyone could add their own Value Services and ingetrate them into the provided city platform.
  • Citizen engagement program
    As part of Sonderborg’s official strategy to become a zero-carbon emission community by 2029, a citizen engagement program has been developed for involving citizens and local housing associations in retrofitting activities.
  • Roadmap2025 - The Integrated Energy Plan (IEP) of Sonderborg
    How to become CO2 neutral by 2029? Sonderborg municipality has compiled the Roadmap2025 using the Integrated Energy Planning approach "Cities4ZERO" methodology, which was developed within SmartEnCity project.