Sometimes it does not take as much as fancy electrical SUVs to have a positive impact on the planet. Being the biggest electricity consumer in Washington D.C., the Blue Plains Advanced Wastewater Treatment plant wanted to lower the environmental burden of their activities. And they didn’t have to look far.
The facility used to treat the wastewater stream in a classical way: it goes though a set of filters to shed the debris, then through a treatment process that seperates the biosolids — the political correct term for poo — from the water. It finally results in 60 truckloads of dump a day that go to landfill.
But since last September, an additional process developed by Norwegian company Cambi and that carries the name thermal hydrolysis is able to produce enough electricity to power 10 500 households or one third of the whole plant’s electricity demand.
View of the thermal hydrolysis installation during construction, with the pulper, reactors and flash tanks in front and the actual digestion silos in the back (photo: PC construction)
Via a cooking step, the biosolids that used to go to landfill, are treated and sterilized. In eight-story high tanks they are then digested by microbes to form methane gas. This is burned to drive turbines that generate energy. The total installation has a capacity of 12MW. From poo to power, very nice. The final left-over biosolid is only half the amount it used to be and thanks to the additional processing it is safe to use as fertilizer in agriculture or gardening.
So next time you’re flushing in Washington D.C., bear in mind that you are generating power –kind of. And some of your biosolids could turn up on the shelves of a home garden store. Maybe you turn out to be buying it back. Think about that.
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Cover Photo by Dean Hochman
