A new industrial facility in suburban Seattle is giving off a whiff of futuristic technology. It can safely treat fecal waste from people and livestock while recycling nutrients that are crucial for agriculture but in increasingly short supply across the nation’s farmlands.
Within the 2.3-acre plant, which smells lightly of ammonia, giant rotating spindles turn steaming-hot septic sludge and biosolids from local wastewater treatment plants into what an engineer calls “poop crepes.” Giant scrapers then deposit the baked biomatter onto a combination conveyor belt and dryer to yield a growing pile of sterilized fertilizer. The waste-processing method uses compressed steam generated in an earlier step, cutting the electricity needed by 95%. Besides the dry fertilizer, the process yields nearly pure ammonia and water.
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.
“It could be really exciting to have a technology like this work if it can help us close the environmental loops on fertilizers and clean water access,” Kimberly Worsham, founder and CEO of the sanitation and hygiene consulting agency FLUSH (an acronym for “facilitated learning for universal sanitation and hygiene”), says of Varcor. “I love seeing new technologies coming on that can revolutionize how we use and reuse.” But Worsham worries that managing such complex technology could prove unsustainable if it doesn’t attract enough workers with the necessary skills.
Securing regulatory permits and licenses could also pose challenges. “When I look at why this has not been done before, it has very little to do with the technology,” says Tartakovsky. “It has everything to do with the regulatory framework.”
Many existing regulations, advocates say, simply never contemplated the potential for wastewater to generate useful products instead of pollutants. The water released by the Varcor plant, for example, is clean enough to be reused, but local officials are proceeding cautiously. To meet discharge regulations, the plant is sending its outflow to a nearby wastewater treatment plant instead of an adjacent wetland.
Despite the challenges, the underlying technology is spreading: Two Midwestern dairies have adopted the system, and a third is working on it. Janicki says the biggest one installed, in Indiana, is five times the size of the Seattle-area septic conversion system, with the potential to convert 250 million gallons a year of cow manure into reusable water, organic fertilizer, and ammonia. The energy-efficient transformation of waste into naturally derived products could eliminate greenhouse-gas emissions from stored manure and traditional fertilizer production while offsetting the energy needed to run the farm.
Waste-to-fertilizer strategies, even if scaled up, won’t be enough on their own to help feed the planet’s burgeoning population. By viewing people as not only consumers but also producers, however, they could help us take far better advantage of some underrated natural assets that won’t run dry anytime soon.
Bryn Nelson is a Seattle-based science writer and the author of Flush: The Remarkable Science of an Unlikely Treasure.
from MIT Technology Review https://ift.tt/vhPA3CW
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