Future-oriented Technologies and Concepts for an Energy-efficient and Resource-saving Water Management (ERWAS)

Work packages in KRN-Mephrec

WP 1: Provision of technical components and proof of practical viability of technologies


Matthias Scherner, Klärschlammverwertung Region Nürnberg GmbH (Sewage Sludge Recycling Nuremberg Region), Adolf-Braun-Straße 33, 90429 Nürnberg

Gerald Grüner, Baumgart Boiler Systems GmbH, Senner Straße 115, 33647 Bielefeld


The technology of metallurgical phosphorus recycling has so far exclusively been tested in a lab reactor. Using a pilot plant on a semi-technical scale, the individual components are to be developed into a robust process chain for simultaneous energetic and material sewage sludge recycling, and proof of the functioning and practical feasibility is to be established. The process chain comprises the following essential process components:

  • sewage sludge preparation for the melt process, comprising drying and briquetting

  • construction and operation of the core components of the shaft furnace (Mephrec reactor)

  • crude gas utilisation, including necessary gas and exhaust air purification

Main objectives of the working package are:

  • Realisation of the demonstration melt-gasification plant for continuous processing of sewage sludge and sewage sludge ash on a semi-technical scale

  • Proof of stable process control and practical feasibility of the main components and the process chain

Work focus is on:

  • Planning and construction of pilot plant by a partner from industry at the Nuremberg Sewage Treatment Plant

  • Commissioning of plant and continuous operation test following a pre-determined test programme

  • Function test of process chain with process optimisation and variation of input materials

  • Determination of guidelines for exhaust air treatment for a large-scale plant

WP 2: Balance of melt-gasification process and process chain and utilisation concept for generated synthesis gas


Sonja Wiesgickl, Fraunhofer UMSICHT, An der Maxhütte 1, 92237  Sulzbach-Rosenberg


The balance of the material streams in the process was calculated in a feasibility study prepared by the ingitec GmbH and needs to be verified by technical measurements. The measurement and analysis programme in the working package will be the basis for the overall process balance. The data will be the basis for the permit, the dimensioning, and the operation of a large-scale plant. Options for utilising the generated synthesis gas which varies with the different operation modes, will be categorised, assessed and compared, according to technical and economic parameters. In addition to the optimum energetic utilisation of the generated synthesis gas, further essential utilisation factors for sewage sludge recycling include the recovery of low-pollution slag containing phosphorus and of the iron alloy. The quality of these process products and residual substances will be documented, and utilisation options will be shown.

Main objectives of this working package are:

  • Knowledge of the entire composition of the output products, of the resources and the output substances, including filter dust

  • Complete process balance with guidelines for technical and operational process optimisation

Working focus is on:

  • Solid substances analysis, gas sample analysis, and examination of slag and dust according to the Landfill Regulations for potentially necessary disposal

  • Examination of thermal utilisation using thermal energy for drying as well as the heating/cooling requirements of the sewage treatment plant

  • Examination of the potential for electricity generation via heat in steam, Sterling or ORC processes, as well as motoric utilisation after gas processing in a combined heat-and-power station, determining required gas quality and processing

WP 3: Integration in the process chain of the waste water treatment plant, management of energy and material streams as a regional service system and regional marketing concept for recycled materials


Christina Tocha, Universität der Bundeswehr München, Institut für Wasserwesen - Siedlungswasserwirtschaft und Abfalltechnik, Werner-Heisenberg-Weg 39, 85577 Neubiberg


Economic viability and practical feasibility of metallurgical phosphorus recycling depend to a large extent on location factors: advantages of short distance, logistic synergies by close linkage of the process with the infrastructure of the waste water treatment process will be shown in concrete terms. The process of melt-gasification of sewage sludge is one part stage in sludge treatment after digestion, dewatering, drying and briquetting. Inexpensive and robust treatment variations will be worked out for the waste water and smell-polluted exhaust air generated in the recycling process, based on analysis and various attempts at reducing them.

The process recovers valuable substances from the sewage sludge. We must examine how these substances can be marketed with maximum use to the economy and what prices can be achieved.

Main objectives of the working package are:

  • Defined and verified location factors for using the process, both positive and negative

  • Regional logistics concept, including marketing strategy for the recycling products, and determination of barriers to acceptance and implementation of the process application

Working focus is on:

  • Analysing existing structure of waste water treatment plant and of disposal paths for sewage sludge. Working out framework and relevant parameters which might influence the concept of energy and materials stream management. Verification of possibility of transferring test results to other locations.

  • Examination and simulation of the influence of exhaust vapours and quench water on the waste water treatment process. Analysis of the effect on purification performance and stability of process stages of different pre-treatments and discharge sites.

  • Summary of legal framework for the approval of the recycled materials for use as fertiliser in Germany and the EU.

  • Definition of quality characteristics and requirements for recycled fertiliser from the overall perspective of the fertiliser industry, traders and potential consumers. Market analysis for determining acceptance and implementation obstacles.

WP 4: Testing alternative input substances


Falko Lehrmann, Innovatherm Gesellschaft zur innovativen Nutzung von Brennstoffen mbH, Frydagstraße 47, 44536 Lünen


With this technology, all input substances containing phosphorus may be utilised. In the pilot plant the utilisation of sewage sludge ash will be tested on a semi-technical scale. In particular, the potential for hardening the ash to a solid form and compressing it will be tested. In addition, process properties inside the shaft furnace will be analysed, and operation of the furnace with and without generation of synthesis gas. The quality of input and output materials will be documented in the analysis program, and technical measurement data for the process will be balanced.

Main objectives of this working package are:

  • Proof of functioning and practical feasibility of the technology for recycling sewage sludge ash

  • Proof of suitability of process for later utilisation of sewage sludge ash from mono-incineration stored in mono-fills

Working focus is on:

  • Proof of function of utilisation of sewage sludge ash of various compositions with part processing, such as briquetting of ash, and subsequent melt-gasification in the pilot plant

  • Clarification of legal framework for utilisation of further substances, such as carcass and bone meal

WP 5: Quality of recycled phosphates and comparison of recycling products with other recycling processes


Prof. Dr. Johannes Pinnekamp, RWTH Aachen, Institut für Siedlungswasserwirtschaft, Mies-van-der-Rohe-Straße 1, 52074 Aachen


The quality of the recycled substance generated by the process is a vital factor for the acceptance of the recycling process in the scientific and economic context. The market value of the recycling product contributes significantly to the economic viability and sustainability of the technology. Therefore an exact determination of the quality characteristics of the recycled product is needed, e.g. toxic substance content, and availability for plants of the phosphates it contains.

In the context of the working package, the potential of the examined metallurgical phosphorous recycling process will be assessed on the basis of characteristics such as energy conversion efficiency, input, and quality of recycled products, and will be compared to other technologies for phosphorus recovery.

Main objectives of this working package are:

  • Proof of quality of recycling products, differentiated according to input materials used, operating mode, and processing of recycled materials
  • Verification of technical potential of the metallurgical phosphorus recycling by comparing and assessing various processes

Working focus is on:

  • Examining solubility of generated slags rich in phosphorus, and assessing mobility of heavy metals

  • Assessing and categorising recycled substances according to the regulation on fertilisers

  • Research on alternative processes for phosphorus recovery. Definition of assessment criteria and comparison of processes.

WP 6: Eco balancing of the process change and eco balance in comparison to alternative disposal paths


Horst Fehrenbach, Institut für Energie- und Umweltforschung Heidelberg GmbH (ifeu), Wilckensstraße 3, 69120 Heidelberg


The energetic and material utilisation of sewage sludge is supposed to make a significant contribution to the sustainability of waste water and raw materials management. In addition to the technical and economic aspects, the eco balance of the impact on the environment is the decisive criterion for assessing the recycling process. Proof has to be furnished that the energy and material streams can be closed as much as possible.

The effect of the various aspects of the concept will be compared to those of alternative processes, and advantages and disadvantages will be quantified. Finally, an overall ecological assessment of the concepts will be made. The system and balance limits contain the entire process chain, from the generation of the sewage sludge in the waster water treatment plant right through to the production of substances which may be substituted for primary products or excluded from the material circuit. All use of resources, emissions to air, water and soil connected with the process, as well as substituted primary products will be included in the eco balance.

Main objectives of the working package are:

  • Eco balance for assessing the regional energy and material streams management concept, comprising the entire life cycle

  • Comparison of the process chain with customary alternatives and recommendation for the best process variant

Working focus is on:

  • Producing life cycle inventory analysis and assessment of effect in up to 10 variants of the process chain

  • Preparing an eco balance for the core process and for the entire recycling system with a sensitivity analysis

  • Comparison of the balance with that of the methods for sewage sludge disposal by mono-incineration in conventional atmospheric fluidised bed combustion, by gasification processes, by co-incineration, as well as by direct application of sewage sludge in agriculture