Experimental plant turns poo to power

This isn't the first time somebody has tried to turn sludge into something more beneficial. In states across the country, including Georgia, Texas and Florida, cities operate sludge incineration plants that produce power or ash that can be used as fertilizer.

About two decades ago, officials spent hundreds of millions of dollars on a sludge processing operation in Los Angeles that was supposed to do exactly whatEnerTech's plant is supposed to do — turn sludge into fuel. That project, however, failed miserably.

EnerTech's Bolin is quick to point out that his project is much different. The so-called "Carver-Greenfield" project back then used oil and forced evaporation to separatebiosolids from sludge, but the process gummed up pipelines and ultimately shut down the system.

"It was much more complicated," said Bolin, who wasn't involved with that project. "We dumbed it down into what's actually a very simple process."

Through a system of pipes and tanks, EnerTech's plant will essentially heat up and pressurize biosolids to the point where they react and break down into carbon and gas. The resulting mushy "slurry" mixture is dried and turned into "e-fuel."

Still, nobody is absolutely sure EnerTech's "SlurryCarb" process will work on the scale planned here. The company has tested the process only with much smaller demonstration plants in Atlanta and in Japan — tests thatBolin is quick to say worked out better than expected.

Local officials here say they aren't too worried about the plant's prospects, especially since — unlike with the project 20 years ago — they don't have any money at risk up front.

"We're all hoping it works, but at this scale it's never been proven," said Torres of the Orange County Sanitation District. "But at least here, we're not investing a dime. If it doesn't work, we'll just go someplace else" with the sludge.

HOW IT WORKS

— Sludge is delivered by tanker trucks from local sewage treatment plants.

— The sludge is pressurized, heated and forced through a reactor.

— Inside the reactor, the the sludge goes through a chemical reaction. Carbon dioxide is stripped out, and the sludge turns into a mushy "slurry" of carbonized biosolids.

— Excess water is removed from the slurry by a centrifuge. Water is sent back to wastewater treatment plants.

— The remaining product is sent through a dryer and turned into pellet-like "e-fuel."

Source: EnerTech