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Chelsea Wold is a freelance journalist based in The Hague, Netherlands and author of Daydream: An Urgent Global Quest to Change Toilets.
Specialized toilet systems extract nitrogen and other nutrients from urine for use as fertilizer and other products. Image Credit: MAK/Georg Mayer/EOOS NEXT
Gotland, Sweden’s largest island, has little fresh water. At the same time, residents are grappling with dangerous levels of pollution from agriculture and sewage systems that are causing harmful algal blooms around the Baltic Sea. They can kill fish and make people sick.
To help solve this series of environmental problems, the island is pinning its hopes on the one unlikely substance that binds them: human urine.
Starting in 2021, the research team began working with a local company that rents out portable toilets. The goal is to collect more than 70,000 liters of urine over a 3-year period in waterless urinals and dedicated toilets at multiple locations during the summer tourist season. The team came from the Swedish University of Agricultural Sciences (SLU) in Uppsala, which has spun off a company called Sanitation360. Using a process the researchers developed, they dried the urine into concrete-like chunks, which they then ground into powder and pressed into fertilizer granules that fit standard farm equipment. Local farmers use the fertilizer to grow barley, which is then sent to breweries to produce ale that can go back into the cycle after consumption.
Prithvi Simha, chemical engineer at SLU and CTO of Sanitation360, said the researchers’ goal is to “go beyond the concept and put into practice” urine reuse on a large scale. The goal is to provide a model that can be emulated worldwide. “Our goal is for everyone, everywhere, to do this exercise.”
In an experiment in Gotland, urine-fertilized barley (right) was compared with unfertilized plants (center) and with mineral fertilizers (left). Image credit: Jenna Senecal.
The Gotland project is part of a similar worldwide effort to separate urine from other wastewater and recycle it into products like fertilizer. The practice, known as urine diversion, is being studied by groups in the United States, Australia, Switzerland, Ethiopia, and South Africa, among others. These efforts go far beyond university laboratories. Waterless urinals are connected to basement disposal systems at offices in Oregon and the Netherlands. Paris plans to install urine-diverting toilets in a 1,000-resident ecozone being built in the city’s 14th arrondissement. The European Space Agency will place 80 toilets at its Paris headquarters, which will begin operations later this year. Urine diversion proponents say it could find uses in places ranging from makeshift military outposts to refugee camps, wealthy urban centers and sprawling slums.
Scientists say that urine diversion, if deployed on a large scale around the world, could bring huge benefits to the environment and public health. This is partly because urine is rich in nutrients that do not pollute water bodies and can be used to fertilize crops or in industrial processes. Simha estimates that humans produce enough urine to replace about a quarter of the world’s current nitrogen and phosphate fertilizers; it also contains potassium and many trace elements (see “Constituents in urine”). Best of all, by not flushing urine down the drain, you save a lot of water and reduce the burden on an aging and overburdened sewer system.
According to experts in the field, many urine diversion components may soon become widely available thanks to advances in toilets and urine disposal strategies. But there are also big obstacles to fundamental change in one of the most fundamental aspects of life. Researchers and companies need to address a myriad of challenges, from improving the design of urine-diverting toilets to making urine easier to process and turn into valuable products. This may include chemical treatment systems connected to individual toilets or basement equipment serving the entire building and providing services for the recovery and maintenance of the resulting concentrated or hardened product (see “From Urine to Product”). In addition, there are broader issues of social change and acceptance, linked both to the varying degrees of cultural taboos associated with human waste and to deep-seated conventions about industrial wastewater and food systems.
As society grapples with shortages of energy, water, and raw materials for agriculture and industry, urine diversion and reuse is “a major challenge to how we provide sanitation,” says biologist Lynn Broaddus, a Minneapolis-based sustainability consultant. . “A genre that will become increasingly important. Minnesota, he was the past President of the Aquatic Federation of Alexandria, Va., a worldwide association of water quality professionals. “It’s actually something of value.”
Once upon a time, urine was a valuable commodity. In the past, some societies used it to fertilize crops, make leather, wash clothes, and make gunpowder. Then, in the late 19th and early 20th centuries, the modern model of centralized wastewater management arose in Great Britain and spread throughout the world, culminating in the so-called urinary blindness.
In this model, toilets use water to quickly drain urine, feces, and toilet paper down the drain, mixed with other fluids from domestic, industrial sources, and sometimes storm drains. In centralized wastewater treatment plants, energy-intensive processes use microorganisms to treat wastewater.
Depending on local rules and conditions of the treatment plant, the wastewater discharged from this process may still contain significant amounts of nitrogen and other nutrients, as well as some other contaminants. 57% of the world’s population is not connected to a centralized sewer system at all (see “Human sewage”).
Scientists are working to make centralized systems more sustainable and less polluting, but starting with Sweden in the 1990s, some researchers are pushing for more fundamental changes. Advances at the end of the pipeline are “just another evolution of the same damn thing,” said Nancy Love, an environmental engineer at the University of Michigan at Ann Arbor. Diverting urine will be “transformative,” she says. In Study 1, which simulated wastewater management systems in three US states, she and her colleagues compared conventional wastewater treatment systems with hypothetical wastewater treatment systems that divert urine and use recovered nutrients instead of synthetic fertilizers. They estimate that communities using urine diversion can reduce overall greenhouse gas emissions by 47%, energy consumption by 41%, freshwater consumption by about half, and nutrient pollution of wastewater by 64%. technology used.
However, the concept remains niche and largely limited to autonomous areas such as Scandinavian eco-villages, rural outbuildings, and developments in low-income areas.
Tove Larsen, a chemical engineer at the Swiss Federal Institute for Aquatic Science and Technology (Eawag) in Dübendorf, says much of the backlog is caused by the toilets themselves. First introduced to the market in the 1990s and 2000s, most urine-diverting toilets have a small basin in front of them to collect the fluid, a setting that requires careful targeting. Other designs include foot-operated conveyor belts that allow urine to drain as the manure is transported to the compost bin, or sensors that operate valves to direct urine to a separate outlet.
A prototype toilet that separates urine and dries it into a powder is being tested at the headquarters of the Swedish water and sewer company VA SYD in Malmö. Image Credit: EOOS NEXT
But in experimental and demonstration projects in Europe, people have not embraced their use, Larsen said, complaining that they are too bulky, smelly and unreliable. “We were really put off by the topic of toilets.”
These concerns haunted the first large-scale use of urine-diverting toilets, a project in the South African city of Ethekwini in the 2000s. Anthony Odili, who studies health management at the University of KwaZulu-Natal in Durban, said the sudden expansion of the city’s post-apartheid borders has resulted in authorities taking over some poor rural areas without toilet and water infrastructure.
After the cholera outbreak in August 2000, authorities quickly deployed several sanitation facilities that met financial and practical constraints, including some 80,000 urine-diverting dry toilets, most of which are still in use today. Urine drains into the soil from under the toilet, and feces end up in a storage facility that the city has emptied every five years since 2016.
Odili said the project has created safer sanitation facilities in the area. However, social science research has identified many problems with the program. Despite the notion that toilets are better than nothing, studies, including some of the studies he participated in, later showed that users generally dislike them, Odili said. Many of them are built with poor quality materials and are uncomfortable to use. While such toilets should theoretically prevent odors, the urine in eThekwini toilets often ends up in the faecal storage, creating a terrible smell. According to Odili, people “couldn’t breathe normally.” Moreover, urine is practically not used.
Ultimately, according to Odili, the decision to introduce urine-diverting dry toilets was top-down and did not take into account people’s preferences, mainly for public health reasons. A 2017 study3 found that more than 95% of eThekwini’s respondents wanted access to the convenient, odorless toilets used by the city’s wealthy white residents, and many planned to install them when conditions allowed. In South Africa, toilets have long been a symbol of racial inequality.
However, the new design could be a breakthrough in urinary diversion. In 2017, led by designer Harald Grundl, in collaboration with Larsen and others, Austrian design firm EOOS (spun off from EOOS Next) released a urine trap. This eliminates the need for the user to aim, and the urine diversion function is almost invisible (see “New kind of toilet”).
It uses the tendency of water to stick to surfaces (called the kettle effect because it acts like an awkward dripping kettle) to direct urine from the front of the toilet into a separate hole (see “How to Recycle Urine”). Developed with funding from the Bill & Melinda Gates Foundation in Seattle, Washington, which has supported a broad swathe of research into toilet innovation for low-income settings, the Urine Trap can be incorporated into everything from high-end ceramic pedestal models to plastic squat pans. Developed with funding from the Bill & Melinda Gates Foundation in Seattle, Washington, which has supported a broad swathe of research into toilet innovation for low-income settings, the Urine Trap can be incorporated into everything from high-end ceramic pedestal models to plastic squat pans. Developed with funding from the Bill & Melinda Gates Foundation in Seattle, Washington, which has supported a wide range of low-income toilet innovation research, the urine trap can be built into everything from models with ceramic pedestals to plastic squats. pots. Developed with funding from the Bill & Melinda Gates Foundation in Seattle, Washington, which supports extensive research into low-income toilet innovation, the urine collector can be built into everything from high-end ceramic-based models to plastic squat trays. The Swiss manufacturer LAUFEN is already releasing a product called “Save!” for the European market, although its cost is too high for many consumers.
The University of KwaZulu-Natal and eThekwini City Council are also testing versions of urine trap toilets that can divert urine and flush out particulate matter. This time, the study focuses more on users. Odie is optimistic that people will prefer the new urine-diverting toilets because they smell better and are easier to use, but he notes that men have to sit down to urinate, which is a huge cultural shift. But if toilets “are also adopted and adopted by high-income neighborhoods – by people from different ethnic backgrounds – it will really help spread,” he said. “We always have to have a racial lens,” he added, to make sure they don’t develop something that is seen as “black only” or “poor only.”
Urine separation is only the first step in transforming sanitation. The next part is figuring out what to do about it. In rural areas, people can store it in vats to kill any pathogens and then apply it to farmland. The World Health Organization makes recommendations for this practice.
But the urban environment is more complicated – this is where most of the urine is produced. It would not be practical to build several separate sewers throughout the city to deliver urine to a central location. And because urine is about 95 percent water, it’s too expensive to store and transport. Therefore, researchers are focusing on drying, concentrating, or otherwise extracting nutrients from urine at the level of a toilet or building, leaving water behind.
It won’t be easy, Larson said. From an engineering standpoint, “piss is a bad solution,” she said. In addition to water, the majority is urea, a nitrogen-rich compound that the body produces as a by-product of protein metabolism. Urea is useful on its own: the synthetic version is a common nitrogen fertilizer (see Nitrogen Requirements). But it’s also tricky: when combined with water, urea turns into ammonia, which gives urine its characteristic odor. If not turned on, ammonia can smell, pollute the air, and take away valuable nitrogen. Catalyzed by the ubiquitous enzyme urease, this reaction, called urea hydrolysis, can take several microseconds, making urease one of the most efficient enzymes known.
Some methods allow hydrolysis to continue. Eawag researchers have developed an advanced process that turns hydrolyzed urine into a concentrated nutrient solution. First, in the aquarium, microorganisms convert volatile ammonia into non-volatile ammonium nitrate, a common fertilizer. The distiller then concentrates the liquid. A subsidiary called Vuna, also based in Dübendorf, is working to commercialize a system for buildings and a product called Aurin, which has been approved in Switzerland for food plants for the first time in the world.
Others try to stop the hydrolysis reaction by quickly raising or lowering the pH of the urine, which is usually neutral when excreted. On the campus of the University of Michigan, Love is partnering with the nonprofit Earth Abundance Institute in Brattleboro, Vermont, to develop a system for buildings that removes liquid citric acid from diverting toilets and waterless toilets. Water erupts from urinals. The urine is then concentrated by repeated freezing and thawing5.
An SLU team led by environmental engineer Bjorn Winneros on the island of Gotland developed a way to dry urine into solid urea mixed with other nutrients. The team evaluates their latest prototype, a freestanding toilet with built-in dryer, at the headquarters of Swedish water and sewer company VA SYD in Malmö.
Other methods target individual nutrients in the urine. They could be more easily integrated into existing supply chains for fertilizers and industrial chemicals, says chemical engineer William Tarpeh, a former postdoctoral fellow at Love’s who is now at Stanford University in California.
A common method of restoring phosphorus from hydrolyzed urine is the addition of magnesium, which causes the precipitation of a fertilizer called struvite. Tarpeh is experimenting with granules of adsorbent material that can selectively remove nitrogen as ammonia6 or phosphorus as phosphate. His system uses a different fluid called regenerant that flows through the balloons after they run out. The regenerant takes the nutrients and renews the balls for the next round. This is a low-tech, passive method, but commercial regenerates are bad for the environment. Now his team is trying to make cheaper and more environmentally friendly products (see “Pollution of the Future”).
Other researchers are developing ways to generate electricity by placing urine in microbial fuel cells. In Cape Town, South Africa, another team has developed a method for making unconventional building bricks by mixing urine, sand and urease-producing bacteria into a mould. They calcify into any shape without firing. The European Space Agency is considering the urine of astronauts as a resource for building housing on the moon.
“When I think about the broad future of urine recycling and wastewater recycling, we want to be able to produce as many products as possible,” Tarpeh said.
As researchers pursue a range of ideas for commodifying urine, they know it’s an uphill battle, especially for an entrenched industry. Fertilizer and food companies, farmers, toilet manufacturers and regulators have been slow to make significant changes to their practices. “There is a lot of inertia here,” Simcha said.
For example, at the University of California, Berkeley, the research and education installation of the LAUFEN save! That includes spending on architects, building and complying with municipal regulations — and that’s not done yet, said Kevin Ona, an environmental engineer who now works at West Virginia University in Morgantown. He said that the lack of existing codes and regulations created problems for the management of the facilities, so he joined the group that was developing new codes.
Part of the inertia may be due to fear of shopper resistance, but a 2021 survey of people in 16 countries7 found that in places like France, China and Uganda, willingness to consume urine-fortified food was close to 80% ( see Will people eat it?’).
Pam Elardo, who leads the Wastewater Administration as deputy administrator of the New York City Environmental Protection Agency, said she supports innovations such as urine diversion as her company’s key goals are to further reduce pollution and recycle resources. She expects that for a city like New York, the most practical and cost-effective method of diverting urine will be off-grid systems in retrofit or new buildings, supplemented by maintenance and collection operations. If innovators can solve a problem, “they should work,” she said.
Given these advances, Larsen predicts that mass production and automation of urine diversion technology may not be far off. This will improve the business case for this transition to waste management. Urinary diversion “is the right technique,” she said. “This is the only technology that can solve home eating problems in a reasonable amount of time. But people have to make up their minds.”
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