Wastewater plant generates power from poop

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Blue Plains wastewater plant converts organic waste into methane gas, which is burned to create electricity.
Blue Plains wastewater plant converts organic waste into methane gas, which is burned to create electricity.

US capital Washington DC's Blue Plains wastewater treatment plant is transforming human waste into clean electricity.

The facility treats 1.4 billion litres of wastewater from over two million households every day, using micro-organisms which ingest carbon and transform nitrates into nitrogen gas. This process renders the wastewater clean enough to flow into nearby water sources - Chesapeake Bay or the Potomac River - without disrupting their ecosystems.

The excrement in the water, if not repurposed as compost, is used to produce electricity. Blue Plains uses a Norwegian hydrolysis (breaking down of chemical compounds through reaction with water) technique to extract organic material from the waste. The plant then uses bacteria to decompose the waste, generating methane gas which can be burned to generate electricity.

The methane produced generates 13 megawatts of electricity, three of which are used for the hydrolysis process. The other ten megawatts are theoretically enough to power about 8 000 households, although in reality this energy is used to power the facility.

"This project embodies a shift from treating used water as waste to leveraging it as a resource," George Hawkins, CEO at DC Water, said at the inauguration of the new facility in October. Blue Plains' use of human waste-generated electricity reduces its carbon footprint by about a third, and saves millions of dollars a year in operating costs, according to engineer Chris Peot.

"It is making use of an asset that we have here at the plant," Peot continues. "For years, we would give it away to farmers for free as fertiliser."

The plan is to add a fourth turbine to its biomass electricity line-up in the near future, which will generate an extra five megawatts of power. In the more distant future, the intention is that the plant becomes fully self-powered, and possibly produces excess energy to sell to nearby residents, Peot says.

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