Urine2Fertilizer@home

The project to develop a domestic urine treatment system makes an important contribution to tackling global challenges in the areas of wastewater management and resource use. The aim is to explore new ways of recovering valuable nutrients and thereby promote both environmental and social aspects of sustainability.

A key motivation behind the project is environmental sustainability: by recovering nutrients from urine, the use of mineral fertilisers can be reduced, thereby minimising environmental impact. At the same time, the project addresses the growing scarcity of nutrients as a global challenge and highlights innovative solutions for how wastewater can be used as a resource in the future.

Whilst conventional wastewater systems have so far failed to exploit potential such as nutrient recovery or the use of waste heat from greywater, this is precisely where the project comes in. It thus makes a direct contribution to the Sustainable Development Goals (SDGs) – in particular SDG 6: Clean Water and Sanitation, and SDG 11: Sustainable Cities and Communities.

The overarching aim is to evaluate and conduct practical trials of the urine treatment process under real-world conditions. The planned demonstration plant is intended to demonstrate that the system is suitable for everyday use and that the intended objectives regarding resource conservation and environmental protection can indeed be achieved.

The aim of the Urine2Fertilizer project is to develop a decentralised, energy-efficient system for recovering nutrients from urine in a building context. Building on previous research findings from Sweden and Switzerland, the aim is to further develop the existing evaporation unit technology for use in regions with colder climates.

The focus is on integration into existing building systems in order to create a practical and sustainable solution for decentralised sanitation technology. In the long term, the process is intended to contribute to closing urban nutrient cycles, conserving resources and enabling local fertiliser production.

To achieve the project objectives, the following key areas of work will be pursued:

• Integration into building systems: Analysis of technical requirements for pipework, storage, supply and exhaust air, and odour management.
• Energy supply: Development of concepts for thermal integration with heating systems and improving efficiency during winter operation.
• Operation and maintenance: Minimising operational costs through automation, safe substrate removal and low-maintenance components.
• Product characterisation: Investigation of micropollutants, assessment of environmental and plant compatibility, and preparation of authorisation procedures for use as a fertiliser.

The technological approach is based on an evaporation reactor with evaporation surfaces, which has so far been designed primarily for freestanding toilets in warm climates. At ambient temperatures of 20–30 °C and relative humidity of 40–80 per cent, evaporation rates of 660 g/h were achieved with an energy consumption of just 63 kWh per year (for a five-person household). This process recovers 95 per cent of the nitrogen and 100 per cent of the phosphorus and potassium, provided that a sufficient dose of Ca(OH)₂ is added.

The innovation of the project lies in the adaptation and system integration of this technology within the European building context. By utilising existing heating systems, automated operational processes and optimised air flow, evaporation performance is to be ensured even at lower ambient temperatures.

The Urine2Fertilizer project makes a significant contribution to the further development of sustainable sanitation systems in Europe. It combines material resource utilisation, energy efficiency and building services engineering into an integrated overall concept. In addition to technical development, scientific insights are expected on the following aspects:

• the behaviour and fate of micropollutants during evaporation,
• optimisation of nutrient recovery under varying climatic conditions,
• assessment of the long-term stability and quality of the fertiliser products produced,
• as well as the basis for the legal and environmental classification of the processes in the context of European fertiliser legislation.

The project thus contributes to the scientific underpinning of circular sanitation technologies and to the promotion of decentralised resource management in the built environment.