P2GreeN at the “ISH Value of Water”: Circular Economy as a Key to Sustainable Water and Nutrient Use

25.03.2025

Dr Stefan Karlowsky explains the connection between wastewater infrastructure, agriculture and the protection of water ecosystems and how P2GreeN addresses these challenges. Photos: ISH Value of Water Conference.

How can nutrient cycles be closed sustainably to protect water resources and ensure the long-term viability of agriculture? This central question was discussed at the “ISH Value of Water” conference on 18 March 2025 – an international event dedicated to the sustainable use and protection of water. The Leibniz Institute of Vegetable and Ornamental Crops (IGZ) was represented at the conference as part of the European research project P2GreeN by Dr Stefan Karlowsky. As an expert in soil fertility and nutrient cycles, he provided insights into the scientific background of the project and explained how innovative approaches to recover and recycle water and nutrients can help conserve freshwater resources and reduce reliance on mineral fertilisers.

The panel discussion, moderated by Anita Beblek, Managing Director of agrathaer GmbH and Project Coordinator of P2GreeN, began with an introduction to the project's objectives. Tobias Stieber (Triodos Bank) outlined the challenges in developing viable business models for circular value chains. Andreas Obersteg (HCU Hamburg) discussed how P2GreeN technologies can be integrated into urban planning and shared insights into the Saint-Vincent-de-Paul sustainable district in Paris, where urine separation is being implemented as an innovative measure for closing nutrient cycles.

Dr Stefan Karlowsky focused on the global challenges addressed by P2GreeN. A key aim of the project is to prevent nutrient pollution in water bodies by employing innovative technologies to recover phosphorus and nitrogen from wastewater systems. At the same time, P2GreeN seeks to reduce agriculture’s dependence on mineral fertilisers by linking urban and rural infrastructures and utilising alternative nutrient sources. Another key aspect of the project is the conservation of freshwater resources through the reuse of treated wastewater and the implementation of resource-oriented sanitation systems.

The subsequent discussion centred on the safety of recycling fertilisers. Dr Karlowsky emphasised that P2GreeN ensures that the recycling fertilisers obtained from human excreta and wastewater are low in contaminants and safe for agricultural use through targeted treatment processes and rigorous monitoring. This is a crucial prerequisite for gaining long-term acceptance of such approaches and advancing the sustainable transformation of agriculture.

Further information about the P2GreeN project can be found on the project website. The conference programme is available here.