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The power of poo

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Missoula's Wastewater Treatment Facility has a new upgrade that turns poop into power. Methane gas recycled from the city's waste has now replaced the natural gas that once heated the entire plant.

"We treat 8 million gallons of wastewater a day," says Treatment Facility Superintendent Starr Sullivan. "About one percent is an organic solid ... some goes right to EKO Compost [a Missoula-based organic compost company], the rest goes to the anaerobic digester."

The mesophilic anaerobic digester that converts human waste to methane looks like a giant hot water heater. It breaks down organic material into carbon dioxide and methane gases by depriving the waste of oxygen. Commonly called "biogas," Sullivan says that about 65 percent of it is then put into the boiler to be used as fuel. The rest is burned off.

Because the carbon is a natural byproduct of human waste, it's considered a cleaner alternative to fossil fuels.

The plant's biggest need for heat, Sullivan explains, is the digester itself. It must maintain a temperature of 95 degrees to break down the waste into biogas. Anaerobic digestion is a simple process employed by treatment plants worldwide and reduces the amount of waste that might end up in landfills or incinerators.

"It's been used for many decades as a fuel source," Sullivan says. "We've had the capability for many years and we've finally made the switch." Recycled methane gas first started heating the plant's boiler 20 years ago. The heating-system renovation is part of a $9 million green technology upgrade for the entire facility.

In addition to the heating system, Sullivan predicts that Missoula's wastewater treatment plant will eventually be converted to biogas-fueled electricity. Facility administrators are looking into the logistics of the switch now, but Sullivan says the cost could be significant.

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