What's New in Poo?

Is poop the latest renewable energy resource, to be included in energy portfolios along with wind, solar, and hydro? A Seattle company has designed a system that uses sewage sludge as an input, and produces clean water, electricity, and ash as outputs.

In 2015, Bill Gates (whose foundation supported the effort) was filmed proudly drinking a glass of water from the system (2-minute video here). This system was specifically designed for use in the developing world, where toilets are commonly built over sludge pits that are periodically pumped and dumped, without treatment, spreading disease and polluting waterways.

The patented pilot system, built in Dakar, is called the OmniProcessor. Explanations of how the treatment system works are vague (it "works by using a distillation process followed by multi stage filtering in the vapor phase...."). Energy produced is limited but continuous, about 250 kW, based on a population of 100,000. SHN wastewater engineer Mike Veach notes that many existing sludge digesters produce electricity by combustion of methane. However, using distillation is not at all common, according to Mike, who has worked on wastewater treatment plants from Willits to Singapore.

Engineers are also working on individual toilet-scale projects that turn poop into water and energy. In South Korea, engineers have installed a "waterless energy-producing toilet system" in a new science pavilion located on the Ulsan National Institute of Science and Technology campus. A grinding system "converts feces into a dry, odorless material" then the material is put into a digester tank, where microbes convert the solids to carbon dioxide and methane. The carbon dioxide is used to culture green algae for biofuel, and the methane is stored for heating fuel.

The South Korean engineers are also developing a smartphone app that calculates your poo's energy value, then awards digital currency to app users (and poopers) to buy salads at the science pavilion. The idea is to convince people that poo is not a waste but a renewable (and plentiful!) resource.

PS. Wondering about the poo emoji? Read its history here.



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