AUGUSTA — The Hatch Hill landfill is expected to produce enough methane gas from decomposing garbage to power generators for the next 15 years, according to a report produced as officials ponder building a system to use landfill gas to produce electricity to power some city and school buildings.

City councilors, after hearing from consultants who produced the report, expressed support for moving ahead with the proposal Thursday, but said they want to see more detailed numbers before committing to it fully.

Paul Porada, an engineer with Portland engineering firm Woodard and Curran, said the landfill should produce enough gas to produce 350 kilowatt hours of electricity a year, for 15 years, and potentially more.

“There is methane being produced today, and that will continue for the foreseeable future,” Porada said.

City officials said the project could be considered viable if it can reliably produce 350 kilowatts of electricity a year, which would be enough to pay back the estimated $1.9 million cost of building the system in 12 to 15 years, with the potential to return revenues beyond that.

Projections in the Woodard and Curran report indicate it can produce that much electricity.

In fact, they anticipate the landfill will generate “significantly” more gas than will be used for power generation, and recommend the city seek other ways to take financial advantage of the additional available landfill gas.

City councilors expressed interest, but At-large Councilor Marci Alexander said she wanted to see a solid estimate of the return on investment before committing to the next step, which would be authorizing the expenditure of about $240,000 to pay for preliminary design for the project.

“I’d like to see the return on investment now, before we spend the $240,000

Ralph St. Pierre, finance director and assistant city manager, said an estimated return on investment could be produced by June. He said, however, he’d like to keep work on the proposal moving.

Mayor David Rollins said he will sponsor an order for councilors to consider, at their business meeting next week, authorizing the expenditure of $240,000 to begin.

St. Pierre said if the numbers don’t look good, the city can halt the project at any time, though he expressed confidence the project will be able to pay for itself, and then some.

The city already captures, and burns off with a flare, methane gas produced at the landfill to prevent it from escaping into the environment.

The payback on the project would rely on controversial net metering rules, which could be changed by the state Public Utilities Commission. Under net metering, utilities credit the bills of small energy generators for the full retail price of all the electricity they send into the grid.

The city proposal would rely on net metering provisions that could allow the city to get about 8.5 cents per kilowatt hour in credits it could use to pay electricity bills at some of the city and schools’ biggest energy-using buildings, such as the Augusta Civic Center and Cony High School. And it would cost an estimated 6 cents per kilowatt hour to generate that electricity at Hatch Hill, using methane from the landfill to power generators that would produce electricity.

The city could designate up to nine sites where the electricity usage would be included in the net-metering plan.

The PUC has recommended changes that could make net metering less beneficial to small power producers, which the city would be. However, an energy services consultant working for the city on the proposal said previously the currently proposed new rules still could allow the city to pay for the energy project and bring the city savings beyond the investment payback.

Producing electricity at Hatch Hill would require the addition of three-phase power at the site, which could be done as part of a separate, approximately $375,000 project. Councilors approved that project in a previous vote.

“I’m ready to move forward on this,” At-large Councilor Corey Wilson said. “It’s a risk, but in my mind I already took that risk when said OK to spending $400,000 to bring in three-phase power.”

While the current landfill is projected to be full in 12 to 15 years, the facility, city officials have said, probably still will be used as a disposal site, where three-phase power would be needed. And the waste there will continue to produce methane gas, Public Works Director Lesley Jones said, for about 25 years after the last day solid waste is put there.

Keith Edwards — 621-5647

[email protected]

Twitter: @kedwardskj