Regional climate-neutral heat supply and electricity generation via industrial waste heat

Energiedienst AG und Evonik Operations GmbH

The Rheinfeld-based company has been feeding its industrial waste heat into a local heating grid since the end of 2020. By doing so, several thousand homes in the surrounding area can be heated in a way that is climate neutral. In the summer months, when the demand for heat decreases, the waste heat is used to generate electricity in an ORC plant.

The production site in Rheinfelden

Participating companies

Energiedienst AG and Evonik Operations GmbH

Project location



Energy/energy generation

Technologies used

Utilisation of external waste heat for heating flats in Rheinfelden and for supplying hot water; Additional ORC plant for generating electricity from waste heat (in summer)

Energy efficiency

Heating energy savings of approximately 20% in the town of Rheinfelden

CO2 savings

6,705 t CO2e/yr


€5.1 million

Payback period

More than 8 years

Funding programmes

KfW (German Credit Institute for Reconstruction) Energy Efficiency Programme – Waste Heat Investment Grant 494


Evonik Operations GmbH, based in Rheinfelden, Germany, manufactures products such as pyrogenic silica and hydrogen peroxide for the food industry. The company generates a large amount of waste heat when cooling exothermic processes. Although the waste heat from several production plants was already being used for internal processes and to heat buildings on the factory premises, some of it remained unused. The waste heat can be used sustainably, nevertheless, for example, for heating and supplying hot water in neighbouring residential areas or for generating electricity. In 2020, Energiedienst AG created a local heating concept for using Evonik’s waste heat externally. The heat is used directly in residential and commercial buildings. As part of the process, 95-degree water is taken from the cooling circuit within Evonik’s production facilities. This water has been fed into the local heating grid in Grendelmatt since the end of 2020 and heats residential buildings there. Energiedienst takes a yearly thermal output of 5.2 MW. This is equivalent to 42 million kWh, which it uses to heat its own buildings and several thousand flats in Rheinfelden in order to provide them with hot water. Energiedienst AG laid around 900 metres of additional piping in order to tap the sources of the waste heat and connect them to Grendelmatt’s local heating grid. In the summer, the waste heat is used in an ORC plant to generate electricity when the demand for heating and hot water drops.

Heating supply diagram:


The project has given concrete impetus to transferring the idea to other regions. The ‘Wärmeverbund Hochrhein’ feasibility study was started on the basis of this project. This study sees all of the industrial heat sources contrasted with the sinks in the municipalities. Further heat decoupling operations have already been planned in Rheinfelden as well. In principle, the project is transferable to a large number of municipalities that have existing local heating grids in the vicinity of companies that generate sufficient waste heat.

Energy Efficiency Award 2021

Award winners 2021

Around 130 applications from Germany and around the world: the Energy Efficiency Award is once again a coveted award in the context of energy… Read more


above: Evonik Industries AG
Graphic below: Energiedienst