We have been responsible for transporting and recycling the almost 80,000t of sewage sludge generated each year by the city's five sewage treatment plants on behalf of Stadtentwässerungsbetriebe Köln (StEB Köln) since 1998. Stadtentwässerungsbetriebe Köln is – with REMONDIS' support – continuously working on optimising its processes. The advantages for StEB Köln are obvious: the complete range of services is provided by REMONDIS – from the in-house logistics, to the transport and recycling of the material. An unusual situation can be found at the main sewage treatment plant in Cologne (one of the largest facilities in the state of NRW with 1,570,000 population equivalents) as the sewage sludge has to be collected and transported away for recycling 365 days a year. 75% of all the sewage sludge generated in Cologne is incinerated and transformed into electricity and steam i.e. it is used for energy recovery; 25% is returned to the natural cycle as a fertiliser and supplier of humus. Together with StEB Köln, therefore, REMONDIS is helping, on the one hand, to reduce consumption of fossil fuels and, on the other hand, to actively conserve natural reserves of phosphate.

Wirtschaftsbetrieb Mainz is an independent public law institution and operates the sewage treatment plant in Mainz-Mombach, the largest in the state of Rhineland-Pfalz. This facility accepts wastewater from approx. 250,000 local inhabitants as well as from commercial and industrial companies located in and around Mainz. REMONDIS Aqua has been responsible for transporting and recycling the sewage sludge (dewatered and dried forms) as well as the screenings, grit chamber residue and sewer sand since 1997. All together, this makes up a volume of over 12,000t of residual materials every year. All of the sewage sludge and screenings are used to recover energy. The grit chamber residue and residue sand from the sewer system are sent for materials recycling. By drying the majority of the sewage sludge and transforming it into energy, Wirtschaftsbetrieb Mainz is – together with REMONDIS Aqua – making an active contribution towards reducing the demand for fossil fuels.