Four-and-a-half billion people around the globe lack access to good sanitation. The methods they typically have access to, however, such as pit latrines and lagoons, are responsible for widespread illnesses and a portion of the greenhouse gases warming our planet.
Agro-ecologists Gavin McNicol and Rebecca Ryals, a former professor at University of Hawaiʻi at Mānoa’s College of Tropical Agriculture and Human Resources (CTAHR), sought to find a way to support sanitation and environmental needs while working with Sustainable Organic Integrated Livelihoods Haiti, a nonprofit that designs, tests and implements sustainable, cost-effective solutions to the country’s sanitation crisis.
In their newest study, McNicol and Ryals show how closing the “poop loop,” or off-site composting of human waste, is a full-cycle sanitation solution that increases safety, sustainability and jobs.
Their study examined the amount of methane, nitrous oxide and carbon dioxide emitted during thermophilic composting of human waste. They determined greenhouse gas emission factors—how much source material escapes into the atmosphere as greenhouse gases during the composting process—and found that composting has a much smaller greenhouse gas footprint than any other non-sewer technology used widely today.
“The compost itself becomes a carbon sink,” Ryals explains. “We showed that spreading compost on grasslands helps the plants take carbon dioxide out of the atmosphere and increases water retention, and it’s an amazing resource to restore depleted soils.”
Their study, “Climate change mitigation potential in sanitation via off-site composting of human waste,” was published in Nature Climate Change.