Holding dirt in hands

Epic Cleantech’s soil amendment

Photo: Matt Simon

There are researchers. Experiment with using the same technique For wastewater solids, primarily converting sludge to a solid product. “If you do pyrolysis — because it’s thermochemical, it’s a hot process — you kill those bacteria, you kill those pathogens, you kill those viruses. It’s very clean,” says engineer Fengqi Yu. are, which the study Wastewater at Cornell University Additionally, sludge is a heavy, inefficient liquid to transport from the facility to the farm. “You carry a lot of water in it, and the density is low. But biochar, it’s light – you can put it in bags – makes it easy to transport.” So producers can more easily ship it to remote farms, but distribute it more locally to urban farms near the wastewater source.

A wastewater facility can also fuel oxygen-free chambers, where microbes digest solid waste and release methane “biogas” as a byproduct. “This biogas can be burned to generate heat,” you say. In Ithaca, New York, that can completely power a wastewater facility, but you’re also experimenting with using biogas to heat nearby buildings, including a medical center. Heating a building with natural gas releases carbon into the atmosphere, but as biogas comes from the crops we eat and enters the sewage system, it increases by pulling carbon down from the atmosphere. , so burning it creates a carbon loop.

Before those microbes make biogas, they also produce volatile fatty acids. Sybil Charville, an environmental engineer who studies wastewater at Colorado State University, says it could be made into jet fuel, or perhaps even fuel for the city’s vehicle fleet. “There’s a lot of value in all kinds of volatile fatty acids,” says Charwell.

In addition to using waste solids as fertilizer, as Epic Cleantech is experimenting with, Scharwell notes that urban farms can benefit from using recycled wastewater that can be used as a disinfectant for use on crops. , but with nitrogen and phosphorus remaining. Plants, but actually difficult to remove from water. “If you can release nitrogen and phosphorus into the system, it’s a very energy-efficient way to use these nutrients directly,” says Scharwell.

All told, the linear path of water—from the source to the city—is beginning to twist. The future of wastewater is circular, recycled into drinking water, compost for urban farms, and energy. Far from being unnatural, drinking recycled toilet water is the kind of resource that nature intended. “Recycling is everywhere in nature,” says Kemps. “If there’s an unused source of energy or nutrients, someone finds a way to use it.” If you can make compost, find a way to purify water, and generate heat and electricity at the same time, that mirrors what we’ve seen organisms evolve over billions of years. Is.”