Energy efficiency

Energy efficiency

New heat supply for Dortmund's city

In the future, the heat supplied to Dortmund's city centre will originate from industrial exhaust heat. The supplier will be KG Deutsche Gasrußwerke GmbH & Co. which is investing around EUR 5.3 million in technical solutions for exhaust heat utilisation – supported by a grant from KfW's Energy Efficiency Programme.

Energy for the city

By 2023, the city heating network of Dortmunder Energie- und Wasserversorgung GmbH shall be replaced by a climate-friendly system.

Dortmund's city centre has already seen a lot of activity: Borussia Dortmund's victories in various football championships have been celebrated here, and every year the world's largest Christmas tree made of around 1,700 red spruce trees is a wonder to behold. In the future, residents of Dortmund's city centre will also have the chance to feel like pioneers when it comes to the city's heat supply. By 2023, the district heating network of Dortmunder Energie- und Wasserversorgung GmbH (DЕW21) in the city centre will be modernised to become an eco-friendly system. Industrial exhaust heat will then replace the gas-based heat supply, making it possible to reduce annual CO₂ emissions by around 45,000 tonnes.

The exhaust heat will be generated in the production facilities of KG Deutsche Gasrußwerke GmbH & Co (DGW). The chemical company is a rarity in Dortmund's industrial scene. In the midst of the structural change that the regional metropolis is undergoing, DGW has been producing mainly carbon black using the furnace-black process since 1936. “Carbon black is primarily used in the rubber industry,” explains Siegfried Moritz, Chief Financial Officer of DGW. “Carbon blacks affect properties such as rolling resistance or rubber elasticity, especially in car tyres.”

Sophisticated measuring technology

The production of carbon black is an energy-intensive process which is monitored by a complex measuring system.

The production of carbon black is an energy-intensive high-temperature process. Raw materials such as coal tar oil are injected into a natural gas flame and incompletely combusted. This produces a residual gas that contains energy which is then converted into electricity. DGW has thus been making a name for itself as an energy supplier for quite some time. Since the electricity produced exceeds its own requirements, excess quantities are fed into the DЕW21 grid. DGW has also been supplying hot water to two district heating networks since 1993.

But the greatest untapped energy potential in the company lies in exhaust heat. In the final stage of production, the carbon black is formed into small beads using water and an additive, before the water is then removed again in rotary dryers. This produces large quantities of steam (known as vapour) that used to be released into the air.

This is why an energy team has been developing energy efficiency solutions in the company since 2013. As early as 2014, Deutsche Gasrußwerke laid the initial groundwork: on one of the three double furnace black roads, the Dortmund-based company installed a steam condenser to use the exhaust heat to generate energy.

Read more under the gallery.

Now the energy supplier DEW21 is building on the exhaust heat from carbon black production. The project: the steam network in the centre of Dortmund, which is in need of rehabilitation, will be replaced by a hot water network, and the steam previously supplied from the Dortmund power plant will be reduced in favour of exhaust heat from DGW. EUR 5.3 million will be invested in the installation of two vapour condensers for the remaining two double furnace black roads at Deutsche Gasrußwerke. “We use energy that is already available and achieve considerably lower pollutant levels, which is consistent with the city's climate goals,” says Siegfried Moritz, CFO at DGW.

This investment is one of DGW's largest single investments since the turn of the millennium. “Mind you, it is an investment in energy generation – not in our core business,” stresses Moritz. This made it all the more important for Dortmund that an investment grant from the “KfW Energy Efficiency Programme – Waste Heat” (nowadays: "Federal funding for energy and resource efficiency in the economy") could be used to finance the project. With this programme, KfW supports non-technology-specific investments in the modernisation, expansion or construction of systems that prevent or utilise exhaust heat. The investment grant is being provided from the Federal Ministry for Economic Affairs and Climate Action funds as part of the “Exhaust Heat Utilisation Initiative”. It generally amounts to 30 per cent of the eligible additional investment costs, or up to 40 per cent for small and medium-sized enterprises.

Siegfried Moritz

DGW Chief Financial Officer Siegfried Moritz is convinced that investments in energy efficiency bring significant returns.

“KfW is contributing EUR 1.6 million to our investment project,” DGW CFO Moritz is pleased to report. “The project would not have come about without these funds.” Siegfried Moritz is convinced that this not only benefits the environment, but also the medium-sized chemical company: “Investments in energy efficiency bring considerable returns. This is also an important contribution to safeguarding our 140 jobs.”

Published on KfW Stories on 30 August 2018, updated on 9 December 2021


All United Nations member states adopted the 2030 Agenda in 2015. At its heart is a list of 17 goals for sustainable development, known as the Sustainable Development Goals (SDGs). Our world should become a place where people are able to live in peace with each other in ways that are ecologically compatible, socially just, and economically effective.