With conventional fuel cells as their model, researchers learned to use similar chemical reactions to make a fuel from microbes in pee.
At the edge of a dirt road flanked by trees and green mountains outside the town of Kisoro, Uganda, sits the concrete building that houses Sesame Girls School, where girls aged 11 to 19 can live, learn and, at least for a while, safely use a toilet. In many developing regions, toileting at night is especially dangerous for children. Without electrical power for lighting, kids may fall into the deep pits of the latrines through broken or unsteady floorboards. Girls are sometimes assaulted by men who hide in the dark.
For the Sesame School girls, though, bright LED lights, connected to tiny gadgets, chased the fears away. They got to use new, clean toilets lit by the power of their own pee. Some girls even used the light provided by the latrines to study.
Urine, whether animal or human, is more than waste. It’s a cheap and abundant resource. Each day across the globe, 8.1 billion humans make 4 billion gallons of pee. Cows, pigs, deer, elephants and other animals add more. By spending money to get rid of it, we waste a renewable resource that can serve more than one purpose. Microorganisms that feed on nutrients in urine can be used in a microbial fuel cell that generates electricity – or "pee power," as the Sesame girls called it.
Plus, urine contains water, phosphorus, potassium and nitrogen, the key ingredients plants need to grow and survive. Human urine could replace about 25 percent of current nitrogen and phosphorous fertilizers worldwide and could save water for gardens and crops. The average U.S. resident flushes a toilet bowl containing only pee and paper about six to seven times a day, which adds up to about 3,500 gallons of water down per year. Plus cows in the U.S. produce 231 gallons of the stuff each year.
Pee power
A conventional fuel cell uses chemical reactions to produce energy, as electrons move from one electrode to another to power a lightbulb or phone. Ioannis Ieropoulos, a professor and chair of Environmental Engineering at the University of Southampton in England, realized the same type of reaction could be used to make a fuel from microbes in pee.
Bacterial species like Shewanella oneidensis and Pseudomonas aeruginosa can consume carbon and other nutrients in urine and pop out electrons as a result of their digestion. In a microbial fuel cell, one electrode is covered in microbes, immersed in urine and kept away from oxygen. Another electrode is in contact with oxygen. When the microbes feed on nutrients, they produce the electrons that flow through the circuit from one electrod to another to combine with oxygen on the other side. As long as the microbes have fresh pee to chomp on, electrons keep flowing. And after the microbes are done with the pee, it can be used as fertilizer.
These microbes are easily found in wastewater treatment plants, ponds, lakes, rivers or soil. Keeping them alive is the easy part, says Ieropoulos. Once the cells start producing stable power, his group sequences the microbes and keeps using them.
Like many promising technologies, scaling these devices for mass consumption won’t be easy, says Kevin Orner, a civil engineering professor at West Virginia University. But it’s moving in the right direction. Ieropoulos’s device has shrunk from the size of about three packs of cards to a large glue stick. It looks and works much like a AAA battery and produce about the same power. By itself, the device can barely power a light bulb, but when stacked together, they can do much more—just like photovoltaic cells in solar panels. His lab has produced 1760 fuel cells stacked together, and with manufacturing support, there’s no theoretical ceiling, he says.
Although pure urine produces the most power, Ieropoulos’s devices also work with the mixed liquids of the wastewater treatment plants, so they can be retrofit into urban wastewater utilities.
This image shows how the pee-powered system works. Pee feeds bacteria in the stack of fuel cells (1), which give off electrons (2) stored in parallel cylindrical cells (3). These cells are connected to a voltage regulator (4), which smooths out the electrical signal to ensure consistent power to the LED strips lighting the toilet.
Courtesy Ioannis Ieropoulos
Key to the long-term success of any urine reclamation effort, says Orner, is avoiding what he calls “parachute engineering”—when well-meaning scientists solve a problem with novel tech and then abandon it. “The way around that is to have either the need come from the community or to have an organization in a community that is committed to seeing a project operate and maintained,” he says.
Success with urine reclamation also depends on the economy. “If energy prices are low, it may not make sense to recover energy,” says Orner. “But right now, fertilizer prices worldwide are generally pretty high, so it may make sense to recover fertilizer and nutrients.” There are obstacles, too, such as few incentives for builders to incorporate urine recycling into new construction. And any hiccups like leaks or waste seepage will cost builders money and reputation. Right now, Orner says, the risks are just too high.
Despite the challenges, Ieropoulos envisions a future in which urine is passed through microbial fuel cells at wastewater treatment plants, retrofitted septic tanks, and building basements, and is then delivered to businesses to use as agricultural fertilizers. Although pure urine produces the most power, Ieropoulos’s devices also work with the mixed liquids of the wastewater treatment plants, so they can be retrofitted into urban wastewater utilities where they can make electricity from the effluent. And unlike solar cells, which are a common target of theft in some areas, nobody wants to steal a bunch of pee.
When Ieropoulos’s team returned to wrap up their pilot project 18 months later, the school’s director begged them to leave the fuel cells in place—because they made a major difference in students’ lives. “We replaced it with a substantial photovoltaic panel,” says Ieropoulos, They couldn’t leave the units forever, he explained, because of intellectual property reasons—their funders worried about theft of both the technology and the idea. But the photovoltaic replacement could be stolen, too, leaving the girls in the dark.
The story repeated itself at another school, in Nairobi, Kenya, as well as in an informal settlement in Durban, South Africa. Each time, Ieropoulos vowed to return. Though the pandemic has delayed his promise, he is resolute about continuing his work—it is a moral and legal obligation. “We've made a commitment to ourselves and to the pupils,” he says. “That's why we need to go back.”
Urine as fertilizer
Modern day industrial systems perpetuate the broken cycle of nutrients. When plants grow, they use up nutrients the soil. We eat the plans and excrete some of the nutrients we pass them into rivers and oceans. As a result, farmers must keep fertilizing the fields while our waste keeps fertilizing the waterways, where the algae, overfertilized with nitrogen, phosphorous and other nutrients grows out of control, sucking up oxygen that other marine species need to live. Few global communities remain untouched by the related challenges this broken chain create: insufficient clean water, food, and energy, and too much human and animal waste.
The Rich Earth Institute in Vermont runs a community-wide urine nutrient recovery program, which collects urine from homes and businesses, transports it for processing, and then supplies it as fertilizer to local farms.
One solution to this broken cycle is reclaiming urine and returning it back to the land. The Rich Earth Institute in Vermont is one of several organizations around the world working to divert and save urine for agricultural use. “The urine produced by an adult in one day contains enough fertilizer to grow all the wheat in one loaf of bread,” states their website.
Notably, while urine is not entirely sterile, it tends to harbor fewer pathogens than feces. That’s largely because urine has less organic matter and therefore less food for pathogens to feed on, but also because the urinary tract and the bladder have built-in antimicrobial defenses that kill many germs. In fact, the Rich Earth Institute says it’s safe to put your own urine onto crops grown for home consumption. Nonetheless, you’ll want to dilute it first because pee usually has too much nitrogen and can cause “fertilizer burn” if applied straight without dilution. Other projects to turn urine into fertilizer are in progress in Niger, South Africa, Kenya, Ethiopia, Sweden, Switzerland, The Netherlands, Australia, and France.
Eleven years ago, the Institute started a program that collects urine from homes and businesses, transports it for processing, and then supplies it as fertilizer to local farms. By 2021, the program included 180 donors producing over 12,000 gallons of urine each year. This urine is helping to fertilize hay fields at four partnering farms. Orner, the West Virginia professor, sees it as a success story. “They've shown how you can do this right--implementing it at a community level scale."
In the U.S., hospitals generate an estimated 6,000 tons of waste per day. A few clinics are leading the way in transitioning to clean energy sources.
She decided to research alternatives for plastic in the medical sector and learned that cups could be reused and easily disinfected. All dentists routinely disinfect their tools anyway and, Stroetzel reasoned, it wouldn’t be too hard to extend that practice to cups.
It's a good example for how often plastic is used unnecessarily in medical practice, she says. The health care sector is the fifth biggest source of pollution and trash in industrialized countries. In the U.S., hospitals generate an estimated 6,000 tons of waste per day, including an average of 400 grams of plastic per patient per day, and this sector produces 8.5 percent of greenhouse gas emissions nationwide.
“Sustainable alternatives exist,” Stroetzel says, “but you have to painstakingly look for them; they are often not offered by the big manufacturers, and all of this takes way too much time [that] medical staff simply does not have during their hectic days.”
When Stroetzel spoke with medical staff in Germany, she found they were often frustrated by all of this waste, especially as they took care to avoid single-use plastic at home. Doctors in other countries share this frustration. In a recent poll, nine out of ten doctors in Germany said they’re aware of the urgency to find sustainable solutions in the health industry but don’t know how to achieve this goal.
After a year of researching more sustainable alternatives, Stroetzel founded a social enterprise startup called POP, short for Practice Without Plastic, together with IT expert Nicolai Niethe, to offer well-researched solutions. “Sustainable alternatives exist,” she says, “but you have to painstakingly look for them; they are often not offered by the big manufacturers, and all of this takes way too much time [that] medical staff simply does not have during their hectic days.”
In addition to reusable dentist cups, other good options for the heath care sector include washable N95 face masks and gloves made from nitrile, which waste less water and energy in their production. But Stroetzel admits that truly making a medical facility more sustainable is a complex task. “This includes negotiating with manufacturers who often package medical materials in double and triple layers of extra plastic.”
While initiatives such as Stroetzel’s provide much needed information, other experts reason that a wholesale rethinking of healthcare is needed. Voluntary action won’t be enough, and government should set the right example. Kari Nadeau, a Stanford physician who has spent 30 years researching the effects of environmental pollution on the immune system, and Kenneth Kizer, the former undersecretary for health in the U.S. Department of Veterans Affairs, wrote in JAMA last year that the medical industry and federal agencies that provide health care should be required to measure and make public their carbon footprints. “Government health systems do not disclose these data (and very rarely do private health care organizations), unlike more than 90% of the Standard & Poor’s top 500 companies and many nongovernment entities," they explained. "This could constitute a substantial step toward better equipping health professionals to confront climate change and other planetary health problems.”
Compared to the U.K., the U.S. healthcare industry lags behind in terms of measuring and managing its carbon footprint, and hospitals are the second highest energy user of any sector in the U.S.
Kizer and Nadeau look to the U.K. National Health Service (NHS), which created a Sustainable Development Unit in 2008 and began that year to conduct assessments of the NHS’s carbon footprint. The NHS also identified its biggest culprits: Of the 2019 footprint, with emissions totaling 25 megatons of carbon dioxide equivalent, 62 percent came from the supply chain, 24 percent from the direct delivery of care, 10 percent from staff commute and patient and visitor travel, and 4 percent from private health and care services commissioned by the NHS. From 1990 to 2019, the NHS has reduced its emission of carbon dioxide equivalents by 26 percent, mostly due to the switch to renewable energy for heat and power. Meanwhile, the NHS has encouraged health clinics in the U.K. to install wind generators or photovoltaics that convert light to electricity -- relatively quick ways to decarbonize buildings in the health sector.
Compared to the U.K., the U.S. healthcare industry lags behind in terms of measuring and managing its carbon footprint, and hospitals are the second highest energy user of any sector in the U.S. “We are already seeing patients with symptoms from climate change, such as worsened respiratory symptoms from increased wildfires and poor air quality in California,” write Thomas B. Newman, a pediatrist at the University of California, San Francisco, and UCSF clinical research coordinator Daisy Valdivieso. “Because of the enormous health threat posed by climate change, health professionals should mobilize support for climate mitigation and adaptation efforts.” They believe “the most direct place to start is to approach the low-lying fruit: reducing healthcare waste and overuse.”
In addition to resulting in waste, the plastic in hospitals ultimately harms patients, who may be even more vulnerable to the effects due to their health conditions. Microplastics have been detected in most humans, and on average, a human ingests five grams of microplastic per week. Newman and Valdivieso refer to the American Board of Internal Medicine's Choosing Wisely program as one of many initiatives that identify and publicize options for “safely doing less” as a strategy to reduce unnecessary healthcare practices, and in turn, reduce cost, resource use, and ultimately reduce medical harm.
A few U.S. clinics are pioneers in transitioning to clean energy sources. In Wisconsin, the nonprofit Gundersen Health network became the first hospital to cut its reliance on petroleum by switching to locally produced green energy in 2015, and it saved $1.2 million per year in the process. Kaiser Permanente eliminated its 800,000 ton carbon footprint through energy efficiency and purchasing carbon offsets, reaching a balance between carbon emissions and removing carbon from the atmosphere in 2020, the first U.S. health system to do so.
Cleveland Clinic has pledged to join Kaiser in becoming carbon neutral by 2027. Realizing that 80 percent of its 2008 carbon emissions came from electricity consumption, the Clinic started switching to renewable energy and installing solar panels, and it has invested in researching recyclable products and packaging. The Clinic’s sustainability report outlines several strategies for producing less waste, such as reusing cases for sterilizing instruments, cutting back on materials that can’t be recycled, and putting pressure on vendors to reduce product packaging.
The Charité Berlin, Europe’s biggest university hospital, has also announced its goal to become carbon neutral. Its sustainability managers have begun to identify the biggest carbon culprits in its operations. “We’ve already reduced CO2 emissions by 21 percent since 2016,” says Simon Batt-Nauerz, the director of infrastructure and sustainability.
The hospital still emits 100,000 tons of CO2 every year, as much as a city with 10,000 residents, but it’s making progress through ride share and bicycle programs for its staff of 20,000 employees, who can get their bikes repaired for free in one of the Charité-operated bike workshops. Another program targets doctors’ and nurses’ scrubs, which cause more than 200 tons of CO2 during manufacturing and cleaning. The staff is currently testing lighter, more sustainable scrubs made from recycled cellulose that is grown regionally and requires 80 percent less land use and 30 percent less water.
The Charité hospital in Berlin still emits 100,000 tons of CO2 every year, but it’s making progress through ride share and bicycle programs for its staff of 20,000 employees.
Wiebke Peitz | Specific to Charité
Anesthesiologist Susanne Koch spearheads sustainability efforts in anesthesiology at the Charité. She says that up to a third of hospital waste comes from surgery rooms. To reduce medical waste, she recommends what she calls the 5 Rs: Reduce, Reuse, Recycle, Rethink, Research. “In medicine, people don’t question the use of plastic because of safety concerns,” she says. “Nobody wants to be sued because something is reused. However, it is possible to reduce plastic and other materials safely.”
For instance, she says, typical surgery kits are single-use and contain more supplies than are actually needed, and the entire kit is routinely thrown out after the surgery. “Up to 20 percent of materials in a surgery room aren’t used but will be discarded,” Koch says. One solution could be smaller kits, she explains, and another would be to recycle the plastic. Another example is breathing tubes. “When they became scarce during the pandemic, studies showed that they can be used seven days instead of 24 hours without increased bacteria load when we change the filters regularly,” Koch says, and wonders, “What else can we reuse?”
In the Netherlands, TU Delft researchers Tim Horeman and Bart van Straten designed a method to melt down the blue polypropylene wrapping paper that keeps medical instruments sterile, so that the material can be turned it into new medical devices. Currently, more than a million kilos of the blue paper are used in Dutch hospitals every year. A growing number of Dutch hospitals are adopting this approach.
Another common practice that’s ripe for improvement is the use of a certain plastic, called PVC, in hospital equipment such as blood bags, tubes and masks. Because of its toxic components, PVC is almost never recycled in the U.S., but University of Michigan researchers Danielle Fagnani and Anne McNeil have discovered a chemical process that can break it down into material that could be incorporated back into production. This could be a step toward a circular economy “that accounts for resource inputs and emissions throughout a product’s life cycle, including extraction of raw materials, manufacturing, transport, use and reuse, and disposal,” as medical experts have proposed. “It’s a failure of humanity to have created these amazing materials which have improved our lives in many ways, but at the same time to be so shortsighted that we didn’t think about what to do with the waste,” McNeil said in a press release.
Susanne Koch puts it more succinctly: “What’s the point if we save patients while killing the planet?”