Decarbonising district heating – Lessons from Sweden

A highlight of the workshop was the presentation by Ariana Tanha, district heating expert from Ekzel AB, who shared Sweden’s experience in building one of the world’s most advanced and sustainable district heating systems, including the economics of combined heat and power plants.

We had the opportunity to speak with Mr. Tanha and ask him key questions about decarbonization, using waste as an energy resource, and the importance of education and transparency for public trust in new environmental technologies.

1. What does the decarbonization of district heating systems mean, and what benefits does it bring?

Decarbonization of district heating means reducing or eliminating fossil fuel use in the production of heat distributed through district heating networks. In Sweden, this shift involves replacing coal, oil, peat and natural gas with renewable and recycled energy sources such as biofuels, waste heat, industrial surplus heat, biogas and heat pumps.

Benefits include:

• Lower greenhouse gas emissions, supporting Sweden’s national climate targets and EU climate goals.
• Improved energy security through reduced dependence on imported fossil fuels (coal, gas and oil).
• More stable energy prices, as renewable and waste-based fuels are less exposed to global price fluctuations. Although after the Russian invasion of Ukraine, the prices of solid biofuels (wood chip, recycled wood, pellet etc.) almost doubled.
• Circular economy- linked benefits, as local waste and by-products are utilized rather than discarded.

However, there are also downsides, for example; the bio-oil, that is used in the reserve and backup boilers inside the heat and power plants, is more expensive than fossil oil.

2. In what ways can waste serve as a resource for district heating? What are the most common misconceptions, and how can they be overcome?

Waste can serve as a valuable energy resource through Waste-to-Energy (WtE) processes, where non-recyclable waste is incinerated to produce heat and electricity. In Sweden, this energy is efficiently fed into district heating networks. Additionally, waste heat from data centers, industries, and wastewater treatment plants can be recovered and reused.

Common misconceptions:

• “Waste incineration discourages recycling.” My answer to this: In Sweden, strict waste hierarchy laws ensure that recycling and reuse are prioritized. Only non-recyclable waste is incinerated.

• “WtE plants are dirty and polluting.” My answer to this: Modern Swedish WtE facilities have advanced cleaning systems of flue gas (the mix of gases and particles produced by combustion) and waste water treatment that remove harmful emissions, meeting some of the strictest environmental standards in the world (usually stricter than EU directives, for example medium combustion plant and large combustion plant directive).

Overcoming misconceptions involves public education, transparent reporting of emissions (which is also regulated by Swedish “self-control law”), and demonstrating the environmental and energy benefits through data and open communication.

3. What are the main advantages of modern Waste-to-Energy (WtE) plants compared to traditional incineration?

Modern WtE plants are highly efficient, clean, and integrated into urban energy systems. Key advantages include:

• Energy efficiency: Modern plants recover both heat and electricity, achieving up to 96% total energy efficiency when connected to district heating networks. This number (96%) does not include heat waste in the district network itself, it is only the relation between energy in (feeded fuel) to energy out (heat and electricity). District heating networks has an efficiency between 8%-20% depending on size.
• Advanced emission control: Technologies such as flue gas condensation, flue gas and wastewater cleaning, and continuous emission monitoring drastically reduce air pollutants.
• Resource recovery: Metals and other materials can be extracted from the waste ash and recycled.
• System integration: They serve as flexible base-load producers, complementing intermittent renewable energy sources like wind and solar.

4. How important are education and transparency when it comes to public acceptance of new environmental technologies?

Education and transparency are critical to building trust and acceptance. When the public understands how technologies work, their environmental impact, and how they contribute to sustainability goals, opposition decreases.

In Sweden, municipalities and energy companies often hold open house events, publish annual environmental reports, and collaborate with schools and universities to increase understanding. Transparency fosters credibility and helps communities feel involved in the transition toward sustainable energy systems.

5. Can you share a successful example from Sweden related to district heating?

A strong example is Stockholm Exergi’s district heating system. It is one of the largest and most advanced in Europe. Its district heating network is 3000 kilometer long and supplies over 90% of Stockholm’s buildings (both public buildings and residents’ homes) with heat.

Key success factors of Stockholm Exergi:

• The system uses a diverse mix of energy sources, including biomass, waste heat from data centers and wastewater treatment, and WtE plants.
• Through projects like Bio-CCS (Bioenergy with Carbon Capture and Storage), Stockholm Exergi aims to become climate positive by capturing and storing biogenic CO2.
• The company maintains high public trust due to transparent operations and continuous sustainability reporting. This despite one of their plants being located in the middle of city (Värtaverket).

This example illustrates how decarbonized district heating can be both technically feasible and socially accepted, contributing to Sweden’s leadership in sustainable urban energy systems.

Alongside Ariana Tanha, the workshop featured Nihad Harbaš, a district heating expert from nLogic Advisory, who spoke about opportunities for decarbonization and financing of district heating improvement projects, as well as the role of district heating in transition plans, covering both national strategies and local realities. The workshop demonstrated how national strategies can effectively align with local needs, and participants gained inspiration and concrete guidance for implementing sustainable solutions in their communities, building on the lessons from Sweden’s advanced and sustainable systems presented by Mr. Tanha.

Interview with Mr. Ariana Tanha has been featured on several news portals. See the full list below: