Tonight, Ann Arbor is living through the biggest derby in the American Midwest: Michigan versus Michigan State, at the “Big House”—the largest stadium in the country. But this year, a story is unfolding beside the arena that appears in neither the game-day program nor the bookmakers’ predictions. At Ann Arbor Golf Club, right across from Gates 2 and 4 of the stadium, stand two yurts with urinals: “Go Blue” and “Go Green.” From 13:00, tailgaters can step into either one and give up what usually goes down the drain without much thought. That liquid has a special destiny today: it will become fertilizer.
The event is called, without false modesty, Piss Off. The first stadium pilot in the United States: the professors’ teams spent no small amount of time on approvals and sanitation protocols, but this year everything fell into place—and the derby acquired a second, liquid standings table.
They are suspiciously simple, like all great things. You enter a yurt in your favorite team’s colors and do what you had planned to do by the stadium anyway. The only difference is that now it is not a stink in the figurative sense, but a donated sample for a bioreactor in the most literal one. Professor Nancy Love’s lab at the University of Michigan is keeping score in gallons: “It will be just under 300 gallons—we have an IBC container for exactly that volume. That’s our limit,” CBS News Detroit quotes her as saying.
Collection is open from 13:00 until the final whistle, the derby itself starts at 19:30, and the winner will be announced Sunday at noon. One particular delight is the merch: the official website sells a T-shirt reading “I made nutrients at the Piss Off,” with the honest disclaimer that the print is still a mock-up and colors may vary.
One detail worth considering in advance: the urinals are waterless and standing-only. The project FAQ tactfully promises to expand the menu of options in the future, but for now, athleticism is welcome.
Behind those two yurts stands the long-running work of the N-E-W Cycles (Nutrient-Energy-Water Cycles Group), led by Love. Her pipeline has four stages, and this is one of those cases where engineering irony is entirely appropriate:
Love’s neighbor in this derby, MSU professor Steven Gasteyer, puts the philosophy more simply than it could possibly be put: “Our waste is food for other organisms, in the simplest terms. And while we can’t do this directly, Dr. Love and her colleagues have developed treatment technology that recovers nitrogen, phosphorus, and potassium from our urine.” For now, the target application is non-edible crops: by Love’s estimate, urine-derived fertilizer can cover 20–25% of the nitrogen needs of lawns, flowers, and other plants we do not eat. Food crops are a subject for future research.
Michigan, though it seems to think it invented everything, is carefully copying a hit from the eco-underground. In Brattleboro, Vermont, the Rich Earth Institute has been operating for more than ten years—a nonprofit that normalized urine donation long before it became a Michigan team sport.
The story began in 2011, when Abraham Noe-Hays and Kim Nace, obsessed with composting toilets, discussed why humanity flushes its own fertilizer into the ocean. In 2012, they founded the institute and collected their first 600 gallons from 60 donors. Today, the Urine Nutrient Reclamation program collects around 12,000 gallons (45,400 liters) a year, involving 244 people from Windham County—architect Kevin O’Brien brings in his contribution to a downtown drop-off point once a week, sometimes by bicycle. Since 2012, the program has saved 2.7 million gallons (10.2 million liters) of perfectly clean tap water that did not have to be flushed down toilets.
Technically, it all looks unremarkable, almost homemade: on the lab wall sits a five-foot stainless-steel box that pasteurizes urine at 80 °C in 90 seconds, meeting EPA sanitation guidelines. Not a 100-hectare factory, but a modest box that Noe-Hays and his colleagues spun off into a separate company in 2019: Brightwater Tools, the very same outfit now making equipment for Michigan too. Six such pasteurizers have already been sold to different states.
Local farmers are lining up for the product. “We apply around 8,000 gallons a year, but we could use ten times more. There just isn’t enough supply yet,” says farmer Noah Hoskins, who has managed to abandon purchased chemical fertilizers entirely on his maple-syrup, flower, and pasture-livestock fields thanks to urine. And according to Nancy Love, who has worked with Rich Earth for a decade now, urine-derived fertilizer cuts greenhouse-gas emissions and requires roughly half as much water as its synthetic counterpart.
Humanity has known that urine is fertilizer since roughly the moment it began growing anything. In Ancient China, it was collected by the bucketful and sold. Rome is a separate poem: urine from public urinals was bought up by fullers, who used ammonia to bleach wool. Emperor Vespasian, who inherited an empty treasury after the civil war, imposed a tax on urine collected from public latrines. When his son Titus reproached his father for the indecency of such income, Vespasian, according to Suetonius, held a coin from the first proceeds under his nose and asked whether it smelled. “No.” — “And yet it comes from urine.” Thus was born the phrase pecunia non olet—“money does not smell”—and Parisian street urinals acquired the name vespasienne nineteen centuries later.
Modern civilization did with all this what it did with most excellent old solutions: diluted it. As Love says without illusions: “Today we dilute our urine with water to a ridiculous degree, send it through a pipe to a treatment plant, and then pump another huge amount of energy into it just to return it to nature in reactive form.” Add outdated building codes that prohibit separating streams—one of the industry’s main brakes, as Food Planet Prize notes. Yet a counterexample is already at work: in Paris, volunteers collect urine to save the Seine and fertilize wheat for baguettes and cookies.
Now for the juiciest layer—the numbers. Urine makes up less than 1% of municipal wastewater by volume, but it contains around three-quarters of the nitrogen and half the phosphorus we flush away—plus potassium, which plants are rather fond of too. Nitrogen lives in it as urea, which soil microbes turn into ammonium—a plant-ready form. Struvite is magnesium ammonium phosphate with six molecules of water in its crystal lattice, and a reputation as a slow-release fertilizer: it does not burn roots, releasing nutrients slowly. Nature truly has nothing to improve upon.
The global arithmetic is more serious than a student prank. According to Prithvi Simha, a researcher at the Swedish University of Agricultural Sciences, SLU, humanity’s urine could replace roughly a third of the nitrogen and phosphorus used by global agriculture. “When there is a shock in the supply chain—how do we grow food? By recycling urine, we add resilience to our food system,” he reasons. He knows the context of 2022 firsthand, when Russia’s invasion of Ukraine—Russia being a major fertilizer exporter—blew up the market. For scale: nitrogen fertilizer production alone accounts for nearly 2% of global greenhouse-gas emissions.
Simha’s spin-off, Sanitation 360, works with Swedish portable-toilet rental companies: collection has grown from 1,500 to 25,000 liters, with a target of 250,000 next year. The dry pellets go to local barley fields, and the beer made from that barley, according to Simha after tasting it, is “exactly like any other beer.” The circle is closed: an amber drink on the way in, amber currency on the way out.
And the final note, which shifts the subject from curiosity to geopolitics: according to the United States Geological Survey, around 68% of the world’s known phosphate-rock reserves—roughly 50 billion tons—lie in Morocco. When one country holds two-thirds of a resource critical to food, a national strategy of “collecting the body’s third output” stops sounding like a joke.
Today, the score will be opened not by a touchdown but by the first gallon donated around 1 p.m. The winner will be announced Sunday at noon, and really, it does not matter whose yurt fills its IBC container first: Matthaei Botanical Gardens, Nichols Arboretum, and the Kellogg Station fields all win—only the sewer loses.
Vespasian spent his whole life fixing Rome’s budget—he inherited the treasury empty after the civil war. A man meticulous down to the last as, he would have wholeheartedly approved of the Michigan approach: pecunia non olet. And so that nobody leaves the field feeling slighted, this derby has its own arithmetic: the main thing is that friendship wins, because the phosphorus belongs to everyone.
Sources: the official Piss Off project website (n-e-wcycles.org), CBS News Detroit, W.K. Kellogg Biological Station (MSU), BBC Future, Food Planet Prize, Deutsche Welle.