As a Circular Cities and Regions Initiative (CCRI) Project, P2GreeN provides circular systemic solutions to the environmental problems of mineral fertiliser use and the high cost of human sewage processing. Finding their innovative solution within the problem, P2GreeN identified the high nutrient content in human waste can be made into bio-based fertilisers to reduce the agricultural industry’s dependency on mineral fertilisers.

The challenge: creating value from lost nutrients

Humans produce huge quantities of urine and faecal waste each year, and sewage wastewater runoff causes environmental pollution and eutrophication due to its high nitrogen and phosphorous nutrient content, which is energy intensive for wastewater treatment plants to remove.

Separately, non-biological, mineral fertilisers used all over the world are not only expensive for farmers but can be devastating to the environment: they emit greenhouse gases (GHGs) when produced, widen the gap in the nutrient cycle and cause eutrophication through fertiliser runoff.

The solution: bio-fertiliser made from human waste

In response, P2GreeN took the innovative step to optimise the nutrient cycle and to halt and eliminate phosphorous and nitrogen pollution by disseminating the concept of human waste recycling in Europe. Through three pilot programmes, the project has developed and shared new solutions for the circular economy with the CCRI community.

As P2GreeN’s coordinators explained, ‘we bring a diverse range of technical, legal, socio-economic, financial and Life Cycle Assessment expertise focused on establishing circular nutrient flows from conventional wastewater streams to the production of solid and liquid fertilisers for agricultural production.’

Resultantly, P2GreeN has successfully tested a business model for developing blueprints and bio-based fertilisers that reduce the nitrogen and phosphorous load for wastewater treatment plants. They reduce the impact of sewage on the environment by diverting human waste into another production cycle, and innovatively reclaim water and nutrients for reuse in farming.

Gotland, Sweden pilot: making bio-fertiliser pellets from urine

To realise the potential of reclaiming nutrients from urine, the project’s pilot in Gotland, Sweden, collected urine from toilets and urinals at events like music festivals and then dried-out and concentrated it by a factor of >25. P2GreeN processed the urine into pellets that have a nitrogen, phosphorous, potassium (NPK) ratio of 15:2:4 and estimates that this process can reclaim 900 kg of nitrogen and 90 kg of phosphorous per year.

These nutrient-rich pellet bio-fertilisers are used by key partner Gotlands Bryggeri to cultivate barley for beer production. This completes the cycle from human waste to beverages sold at events where the urine was initially collected, without using mineral fertilisers mined outside of the EU.

This sustainable and circular approach to nutrient reclamation valorised the production of bio-fertiliser pellets and reduced the NPK load on wastewater plants. The Gotland pilot programme aims to expand its innovative impact by obtaining 150 m3 of urine by the end of 2026 to help close the nutrient loop in the agriculture industry.

Hamburg and Hanover, Germany pilot: urine to liquid fertiliser and faeces to humus fertiliser

Similarly, the project’s pilot in Hamburg and Hanover, Germany, found great success collecting human waste to produce fertiliser and cultivate crops, this time with the difference of collecting human faeces as well as urine.

As P2GreeN coordinators explained, ‘the system from VunaNexus, converts urine via a bioreactor into a liquid fertiliser. This is especially relevant for horticulture, gardens, and parks. The second technology, developed by Goldeimer, converts human faeces into humus fertiliser thereby also enhancing the soil properties and soil fertility.’ The project’s partner Vagtshoff uses this bio-fertiliser to cultivate rye and barley for beer production.

P2GreeN succeeds at closing nutrient cycles for nitrogen and phosphorous in the Hamburg-Hanover metropolitan area reclaiming approximately 1140 kg of nitrogen and 320 kg of phosphorous per year in this pilot programme alone. The project does this while avoiding critical emissions to the Elbe and Weser river basins, which has helped reduce the current German water and nutrient crises declared by 10 % of Germany’s municipalities.

Axarquia, Spain pilot: water reclamation and bio-fertiliser production

The third pilot scheme goes one step further than producing bio-fertiliser, aiming to also reclaim water from urine. To do so, the pilot in Axarquia, Spain, uses water reclamation technology and a smart irrigation system that controls the amount of water applied to land, reducing water waste in farming.

The process starts by collecting wastewater from Algarrobo’s municipal wastewater treatment plant and removing disease pathogens and contaminants in a water reclamation plant using disc filtration and ozone disinfection (an effective way to sanitise water contaminated with industrial by-products). This process transforms the urine into a nutrient-rich wastewater, reclaiming 3650 m3 of water per year.

Reclaimed water is then used to fertigate (simultaneously fertilise and irrigate) avocado and mango crops in Spain. The process can be supplemented by mineral fertilisers or thinned with local water, under the control of an innovative smart fertigation tool. This tool analyses the level of nutrients and elements in the soil, fostering a prescriptive, sustainable and circular approach to nutrients and water use in the region and simultaneously reducing NPK loads for wastewater treatment plants.

P2GreeN’s support to other projects

Reflecting on their success, the coordinators behind the project explained the benefits of being part of the CCRI, saying ‘the CCRI gives P2GreeN access to a wide European network with people working in different areas but who are all dedicated to establish circular economy initiatives that can pave the way for a broader uptake across all regions in Europe.’

The project’s three pilot schemes have proven the success of using a circular system within the agricultural industry, which P2GreeN’s coordinators wish to share across the CCRI: ‘the CCRI community of practice is a very valuable forum for P2GreeN to exchange knowledge, share experiences and learn from others.’

Ultimately, P2GreeN’s innovative approaches to reusing human waste are some of the first steps taken in Europe to replace conventional mineral fertilisers and reduce the industry’s dependency on phosphorous mined outside of the EU. P2GreeN succeeded in this while creating a high-value fertiliser product, producing beer through a circular nutrient loop, and reducing GHG, water processing costs, eutrophication and water waste.

If you are interested in learning more about the P2GreeN project and finding out about its work with the CCRI, visit the project’s website.