Cross-Cutting Topic 2

© Albrecht Fietz,

Cross-Cutting Topic 2: Sustainability assessment

Objective of the Cross-Cutting Topic

Implementation of a holistic sustainability assessment of different phosphorus recycling processes

  • Ensuring the comparability of the LCA studies of the subprojects.
  • To ensure the comparability of the different recycling technologies, a uniform collection of data, a clear definition of system boundaries or balance frameworks as well as further assumptions (e.g. on the use of chemicals and transport) are required. These framework conditions will be discussed and agreed upon in close exchange with the subprojects and subsequently elaborated in a criteria catalog.
  • Study on the social acceptance of secondary fertilizers
  • The phosphate-containing secondary fertilizer recovered from sewage sludge or sewage sludge ash will have to compete with primary fertilizer on the open market. In order to prepare a successful market entry, the acceptance of the market/the market participants should be researched at an early stage within the framework of a social study in order to identify obstacles in the market introduction and to initiate suitable measures.
  • Economic feasibility study
  • The future price of the secondary fertilizer will be one of the decisive factors in determining whether the product becomes established on the market. For a comparable profitability assessment of recovery technologies, uniform standards and criteria must be developed that take into account both investment costs (planning, construction, reinvestment, etc.) and running costs (personnel, energy, operating resources, costs from legal requirements, feedstock, etc.).

Work Progress

As part of the cross-sectional topic, numerous bilateral as well as cross-project discussions were held and a workshop took place on the topic of life cycle assessment. In addition, the different assessment approaches were compiled via a questionnaire campaign in order to identify the essential process steps of the procedural approaches that require cross-project coordination. From the evaluations of the questionnaires, the discussions and, in particular, the workshop, a number of points emerged that need to be harmonized in the further course of the project. For example, the fertilizing effect of the secondary fertilizers, the potential consideration of the application of the secondary fertilizers, the definition of the system boundaries taking into account transfer points to downstream and upstream processes or also the allocation of credits for the phosphorus fertilizer and other secondary products are to be mentioned.


The development of a criteria catalog for the preparation of comparable life cycle assessment studies for phosphorus recycling continues to be a major challenge. Furthermore discussions are planned in order to identify a common denominator for the basic structure of the life cycle assessments in close coordination with the subprojects. The cross-project exchange required for this will be continued at a workshop in 2022, at which other topics of the cross-sectional topic will also be addressed.

Contact Person

Institute for Sustainability in Civil Engineering (INaB), RWTH Aachen University
Dr.-Ing. Roland Meyer
Tel.: +49 241 80 22762