How poop could help feed the planet

This system, called Varcor, was designed by the Seattle engineering firm Sedron Technologies and is owned by the San Francisco–based company Generate Upcycle. Wastewater treatment plants across the country are using high heat, composting, and devices akin to pressure cookers to transform leftover biomass into rich fertilizers, mulches, and other soil additives with names like Bloom and TAGRO (short for “Tacoma Grow”). Some process the wastewater in a separate step to extract phosphorus—an essential plant nutrient and a common element in the human diet—and layer it to form round pellets, in a technique a bit like building pearls. This technology, developed by a St. Louis–based company called Ostara, creates a slow-release fertilizer that can be sold back to farmers. 

“We love tackling the yuck factor head-on,” says the CEO of Epic Cleantec, which transforms wastewater into clean water and a natural soil additive.

Even portable toilets can be vehicles for nutrient recovery, through nitrogen-capturing methods developed by “peecycling” groups like the Rich Earth Institute and Wasted in Vermont and by Sanitation360 AB in Sweden. Because our protein-rich diets contain abundant nitrogen, the element can be readily recycled from both urine and feces.

Making fertilizer from the nutrients that we and other animals excrete has a long and colorful history; for generations it helped Indigenous cultures around the world create exceptionally fertile soil. These systems fell out of favor in Western culture, but researchers and engineers have joined advocates in reframing feces, urine, and their ingredients as invaluable natural resources to reuse instead of waste products to burn or bury. Several companies are now showing how to safely scale up the transformation with energy-efficient technologies. “We love tackling the yuck factor head-on,” says Aaron Tartakovsky, cofounder and CEO of Epic Cleantec, which uses a chemical reaction and heat to transform wastewater into clean water and a natural soil additive.  

A recent review in the Journal of Environmental Management, in fact, touts wastewater treatment plants as “renewable biological nitrogen mines” that can supply the essential but expensive component from reclaimed sewage sludge at a time when many farmers are finding it harder to obtain. Sewage can, the authors conclude, “become an important raw material for the sustainable production of organic-mineral fertilizers from renewable resources available locally, with a low carbon footprint.” Extracting nitrogen and phosphorus for reuse can also help remove those pollutants from the plants’ outflow and reduce the amount of organic matter destined for landfills and manure lagoons, which store and manage huge concentrations of livestock waste. Reinserting ourselves into nature’s recycling system, in other words, could help us meet the planet’s growing food needs without unduly fouling the environment. 

The Varcor system heats the incoming poop and separates it into solid matter and vapor. A process called mechanical vapor recompression allows the compressed steam to be reused as a heat source while the water and ammonia vapor are separated and distilled. The conveyor belt/dryer carries the remaining solids to the giant crepe-making spindles and then into a waiting truck below. The plant is now selling three to four truckloads of this dry fertilizer to farms every week. Stanley Janicki, chief revenue officer for Sedron Technologies, says several companies are also interested in using the ammonia product to make fertilizer instead of deriving it from fossil fuels.