"It's a good technology. The problem is you have to tell people you're going to bring [sewage] into their building," he said.
The sewage does not actually flow through buildings. At the facility in the Waterfront South section of Camden, which takes effluent from across the county, heat from raw sewage will be extracted in a closed system, then pumped through the facility's existing heating system, reducing its need for electricity.
The project is one of 18 funded by PSE&G toward meeting a state requirement that utilities invest in improving energy efficiency.
"Hopefully, one day we will be using this technology to heat hospitals and hotels and shopping malls," said Andy Kricun, executive director of the Camden County Municipal Utilities Authority.
Geothermal technology - which takes heat from the earth - has come into wider use around the United States as energy prices have risen, DiEnna said.
It can use heat from deep underground, which stays a constant temperature, to heat or cool office buildings. Or it can use superheated water from underground to drive turbines that generate electricity.
"It's a 60-year-old technology that is gaining ground," DiEnna said. "The cost of energy is so dramatic right now, and 55 percent of an electricity bill is heating or cooling or water heaters."
The question is: How much money will the Camden project and others save?
PSE&G estimates the Camden sewage facility will save about $80,000 a year on electricity bills, about a quarter of its heating costs.
"It's a modest savings," Kricun said. "But you have to think about the environmental benefit, which is not insignificant."
Calculating the benefits of geothermal energy, and of environmental projects in general, can be tricky.
When the Friends Center in Center City spent $1.3 million to drill 1,500-foot-deep holes into the ground in 2008, it was told the system would nearly halve its energy costs.
Instead, those bills decreased about 35 percent, executive director Patricia McBee said.
"That's still pretty darn good, but not as much as we were promised," she said.
Contact staff writer James Osborne at 856-779-3876 or firstname.lastname@example.org.