Tag: Source-separating sanitation systems

Stabilising human urine before it hydrolyses has long been one of the more persistent operational challenges in urine-diverting sanitation systems. Our recently published study introduces a building-scale on-site reactor that passively doses freshly collected urine with sparingly soluble fumaric acid, offering a low-tech, cost-effective, and robust solution that complements front- and back-end innovations in urine source separation.

In contrast to soluble acids like citric or oxalic acid, which require continuous or precise metering to avoid oversaturation or pH swings, fumaric acid’s low solubility (6–11 g/L in urine) lends itself naturally to passive dosing. We developed a 5-L reactor where 250 g of fumaric acid was pre-loaded and gradually consumed as urine was incrementally added. Over 15 days, the system mimicked 263 urination events, treating 46 L of urine while maintaining pH < 4.0 for the majority of the experiment, successfully inhibiting urease activity and preventing mineral precipitation.

One of the more novel aspects of this study was our use of UV-Vis absorbance as a practical, real-time surrogate for process monitoring. ΔAbs221 was found to reliably track fumaric acid saturation and consumption in the reactor, providing earlier indication of reactor exhaustion than pH measurements. Similarly, ΔAbs660 was shown to be a useful proxy for assessing solids settling, particularly relevant when the fumaric acid transitions from supersaturated to undersaturated states.

From a design and scaling perspective, the passive dosing mechanism offers a number of practical advantages. There is no need for metering pumps or automation to control acid input. Fumaric acid can simply be pre-loaded in excess, creating a buffered environment where low pH is maintained until the acid is exhausted. This makes it ideal for decentralised or semi-centralised sanitation systems in public buildings or housing blocks. While the reactor in this study was operated under controlled lab conditions, the materials, energy input, and mixing protocols were deliberately chosen to mimic real-world use. The estimated operating cost—less than US$ 5 per person per year—compares favourably to existing benchmarks, including the Gates Foundation’s target for non-sewered sanitation solutions.

A key outcome of this study is that stabilised urine retained nitrogen in the form of urea, and did not exhibit significant losses in other key macronutrients—except for about 20% sulphate, which warrants further investigation. The system is therefore compatible with downstream processing aimed at nutrient concentration, e.g., evaporation or freeze-drying. Looking forward, integrating such a passive stabilisation reactor upstream of back-end treatment units could simplify plumbing, reduce pipe blockages, and improve user acceptance, particularly in building-scale deployments. When combined with turbidity sensors, occupancy-based drainage triggers, and modular back-end technologies, this approach offers a feasible path toward closing the loop on nutrient flows without increasing user burden or operational complexity.

The full article is available open access at Frontiers in Environmental Science: https://doi.org/10.3389/fenvs.2025.1546396.

In January, The Swedish Water and Wastewater Association, Svenskt Vatten, hosted the National Wastewater and Environment Conference (NAM) in Uppsala, Sweden. Sanitation360, in collaboration with SLU’s Department of Energy and Technology, introduced a new innovation in sustainable sanitation during the conference. As part of the P2GreeN project, we installed two pop-up urinals: a male urinal (from Urimat) and our newly designed unisex urinal, both designed for urine collection.
This event marked the debut of our first prototype of the unisex ceramic urinal (photo on the right), an important step towards creating more inclusive and sustainable restroom solutions. Our goal was to provide equal access to urinals for all genders and promote more sustainable toilet habits by recycling urine. Historically, urinals have mainly been available for men, but with this new design, we make them accessible for everyone.

We also sought to improve this design based on real user feedback. Attendees who had the opportunity to try out the new urinals were invited to fill out a short survey to share their experience. Their input will help us refine and optimize the prototype, ensuring it meets the needs of all users while supporting environmental sustainability. Here’s the survey in case you got the to try our unisex urinal and still want to provide some feedback, thank you: https://forms.gle/cV8kgd6TpTG9gncDA

By reducing queues at major events like conferences, festivals and football games, we hope to make the restroom experience more convenient and equitable for everyone. Looking ahead, we will be showcasing the same pop-up urinals at upcoming conferences in Sweden related to the environment and wastewater. We’re excited to continue this journey and promote a future where efficient and sustainable sanitation is accessible to all!

Prithvi Simha has been chosen as an Early Career Editorial Board member for the Journal of Environmental Chemical Engineering (JECE). This role is very special to Prithvi because JECE is the journal where his academic publishing journey began in 2014 with his first paper on urine recycling. He looks forward to working with the JECE team and contributing to the field of environmental chemical engineering.

More info about the journal: https://www.sciencedirect.com/journal/journal-of-environmental-chemical-engineering

Our recent study explores an innovative approach to sustainable agriculture by combining dehydrated human urine with various organic wastes to create circular fertilizers. This research addresses a critical need: reducing reliance on inorganic fertilizers while managing nutrient cycles more effectively. By tailoring these fertiliser blends to meet the specific macronutrient demands of 15 major crops, we aim to provide a viable alternative that supports both crop yields and environmental sustainability.

We used a reverse blending modeling approach, analyzing data from 359 different organic wastes to simulate potential fertilizer combinations. The challenge was to identify materials that could balance the nutrient profile of dehydrated human urine, which is naturally high in nitrogen but lower in phosphorus and potassium. Through this process, biochars and ashes emerged as particularly promising blending materials due to their low nitrogen content and higher levels of phosphorus and/or potassium. This made them ideal for pairing with human urine, which helped offset the typical nutrient imbalances when used alone.

Hello! My name is Chibambila Simbeye, and I am thrilled to introduce myself as a new member of the SLU Urine Research Group. I hail from Chingola, a small mining town in the Copperbelt province of Zambia. My background is in civil engineering. I hold both a bachelor’s and a master’s degree in this field, with my master’s focusing on water engineering. For my master’s thesis, I explored the recovery of phosphorus from human urine in the form of vivianite. This further fueled my interest and passion for innovative sanitation solutions.

At SLU, my research will focus on developing alkaline urine dehydration technology for decentralized sanitation systems. I am optimistic that the results of my research will be adopted and implemented to improve sanitation practices around the world. If you have an interest in urine treatment or water and sanitation, I would love to exchange ideas with you.

Why do I do what I do? I firmly believe that access to sanitation is a basic human right that remains unfulfilled in many parts of the world, particularly in developing countries. Urban sprawl has led to the growth of large unplanned settlements where traditional centralized sanitation systems are often unfeasible. I am convinced that decentralized systems, which incorporate source separation, are the key to addressing these challenges sustainably. To achieve this, we need to understand how to manage each waste fraction effectively, with urine being a crucial component.

In addition to my academic pursuits, I am a computing tech enthusiast and an avid fan of competitive sports, especially football and I am always up for a football discussion. I also like to play chess occasionally, so feel free to reach out if you’d like to have a game!

Looking forward to connecting with you all and contributing to the exciting work happening at SLU.

Kale Bwangu! (Direct translation: long ago fast, Meaning: Already done and used a confident salute for mutual understanding)

 

 

My name is Christoffer and I started working here in September 2023 as a PhD student. The field of research I work in is turning urine from urine diverting toilets into a dehydrated, commercial fertilizer. Urine diverting toilets commonly have problems with precipitation forming, clogging the pipes. The scope of my research is to investigate this process and come up with solutions so that the pipes can easily be kept clean, which would open up for wider implementation of those toilets.

My background is in Environment & Water Engineering, which I studied here in Uppsala, my home town. I have been interested in research my whole life, and wanted to become a PhD student for as long as I knew of the concept. I am very curious and am at my happiest when I get to perform experiments and analyse the results.

Apart from research, my interests are many and varied. I sing and play a lot, both choir music as well as traditional Scandinavian & Celtic folk music. I nourish a passion for nature and love to go hiking. I am also very interested in languages, different cultures and history, and frequently discuss those topics with people from other countries as well as other swedes, preferably over a fika!

In a recent article published in BMC Environmental Science, Prithvi Simha and Gert van der Merwe argue that the term “green” ammonia is misleading, inaccurate, and overly simplistic.

Both brown ammonia and “green” ammonia are produced using the Haber-Bosch process. While brown ammonia is made using hydrogen extracted from fossil fuels, green ammonia uses hydrogen derived from renewable energy-powered electrolysis of water, thereby “greening” and decarbonizing ammonia synthesis. However, the nitrogen needed for Haber-Bosch ammonia synthesis is extracted from the atmosphere, an energy-intensive process that remains fundamentally linear for both types of ammonia. This anthropogenic nitrogen extraction has nearly doubled global nitrogen fixation, and already pushed the biogeochemical cycle of nitrogen beyond its safe planetary boundary.

Decarbonizing the global economy is essential, but focusing solely on reducing carbon emissions is shortsighted. To truly merit a green label, we argue that the fertilizer industry must adopt a planetary boundaries framework that extends beyond the current industry focus on merely offsetting or reducing carbon emissions from fertiliser production. The industry has a significant impact on nitrogen and phosphorus nutrient cycles and thus, has extended producer responsibility for minimising the environmental impacts of its products.

We think that the fertiliser industry should strive for creating products that substantially reduce reactive nitrogen and phosphorus fluxes to ecosystems. One solution here is to engage in the large-scale production of bio-based fertilizers. For instance, recycling humanurine alone could substitute about 25% of the nitrogen and phosphate fertilisers used in agriculture globally. Such recycling could offset the demand for anthropogenic nitrogen fixation via green/brown ammonia synthesis, while aligning food systems more closely with the principles of a truly green and circular economy.

Let’s redefine what it means to be “green” by considering the full environmental impact and embracing genuinely sustainable alternatives.

Read the full article here: https://lnkd.in/dKmxCz_S

Helloy! My name is Yulia, I’m coming from Finland, but study in Umeå University. About a year ago I finished bachelor programme in Life Sciences with specialisation in molecular biology, and now I’m studying master’s programme in chemistry. And though I’m planning to specialise in medicinal chemistry, my interests lay wide. Among them is wastewater treatment, for it’s both very important and also very interesting subject. This led me to Prithvi Simha’s research group. I’m here at SLU for a six-week internship, studying the potential of persulfate activation in urine with Ali Peter Mehaidli. Activation of persulfate will result into formation of sulphate radicals, and those in their turn will be degrading organic compounds in urine. Thus, the potential outcome of this study is to find a method of improving degradation of organic compounds in urine, while preserving nitrogen and phosphorus.

Hi! My name is Nathanaël, but everyone calls me Nate, so feel free to do the same. I am currently interning with the Environmental Engineering Research Group at SLU for three months, and I’ll be here until July 26th. I come from Strasbourg, France, where I attend ENGEES (National School of Water and Environmental Engineering, Strasbourg). Our focus is on all aspects of water, from the smallest water cycles to the bigger picture. Next school year will be my final year before I become an engineer. My specialty is water treatment, and I aspire to work in wastewater treatment plants or in a design office that deals with their dimensioning or startup. This interest led me to contact researcher Prithvi Simha, as I found the subject of urine separation particularly fascinating and underexplored at my school. I’m currently working and learning with PhD student Christoffer Parrow Melhus on urine collection pipes. In these pipes, urea breaks down into ammonia and carbon dioxide, leading to precipitation that can cause complete blockages. On a personal note, I enjoy discovering new things and was actively involved in student life at my school, organizing events for my peers. In my spare time, I like to go fishing to recharge my batteries.