A major new garbage-to-energy plant could soon become the centerpiece of efforts to manage O'ahu's growing waste disposal problem — if the city decides to build it.

Companies eager to provide such a facility have lobbied officials for years on competing technologies, including some that remain unproven on the scale the island needs.

A deal has remained elusive, while controversy about the future of the Waimanalo Gulch landfill near Kahe Point simmers.

But three companies have formally bid on a complex new proposal to build and operate a new alternative energy plant, modify and operate the existing H-Power incinerator-generator for 20 years, or a combination of both.

The contract is expected to be worth $350 million or more, and a decision is due in January.

The landfill's state operating permit is set to expire four months later, and some Leeward Coast businesses and residents hope it will be shut down for good. Whether that is a viable option remains unclear.

The island produces about 1.6 million tons of trash and debris each year, and that is expected to increase by 20,000 tons a year for the near future, according to recent studies.

More than 300,000 tons of garbage already go into the landfill each year, along with 168,000 tons of ash and residue from H-Power.

A new plant could eliminate as much as 400,000 tons of garbage per year, in addition to the 600,000 tons H-Power already handles, according to city construction outlines.

But a new plant would not likely be ready for operation until 2011 or later. Even then, the island would still need a landfill — at Waimanalo Gulch or elsewhere — for any waste that can't be burned, recycled or otherwise eliminated, city officials say.

And unless H-Power is upgraded, it will continue to be shut down periodically for maintenance, leaving tons of trash piling up in the gulch landfill or another spot.

WAIMANALO GULCH

Mayor Mufi Hannemann is working to extend the landfill's current permit for two years, while the city conducts an environmental study to support a separate request to expand the site and keep it open 15 years longer.

In the meantime, the city may soon start shipping some trash to a Mainland dump and launch a curbside residential recycling program to help decrease the trash flow.

If the city decides on a new waste-to-energy facility, it would be built next to the 17-year-old H-Power plant at Campbell Industrial Park.

H-Power uses trash combustion to heat two huge boilers, which produce steam that powers a turbine and generates up to 46 megawatts of electricity.

The new plant could be based on a different technology, such as gasification or vitrification, which burn waste at a higher temperature and leave less ash.

Officials are now evaluating whether the three proposals that were submitted meet the city's qualifications. They will ask for final price offers in October. The projects could be financed through city bonds, or by private investors who would recoup their money through operating fees or a sale to the city.

Covanta Energy Corp., which operates H-Power, confirmed that it is among the bidders, but details of its proposal remain confidential. The company's H-Power contract expires in 2010, and it hopes to continue beyond that.

"There are lots of possibilities, so whoever bid had the option to bid different packages," said H-Power business manager Rodney Smith. "It's a really big investment for the city, so they need to take their time and make a good decision."

Waste Management Inc., the company that operates Waimanalo Gulch for the city, declined to say whether it or an affiliate submitted bids. The firm and a subsidiary were among dozens of companies that received copies of the city's request for proposals.

TRASH-TO-MAINLAND IDEA

At least three Mainland firms hope to land a contract to ship some trash to Washington state or Oregon. But so far, there's nothing to bid on.

City environmental officials drafted a bid request package in mid-July, but said the plan raised "major" concerns from attorneys and finance officials.

The documents are now being revised to include a two-step process, in which bidders submit their qualifications before specifying prices for shipping.

Only one firm, Hawaiian Waste Systems, has obtained all the necessary permits to begin a trash-shipping operation from here.

The Seattle company hopes to begin shipping more than 100,000 tons a year to a major regional landfill in rural Washington while the new waste-to-energy facility is built — or longer if that plan stalls. The company says it could also handle ash from H-Power.

Hannemann is expected to announce details of a curbside recycling project late next month, and it could begin by October.

Hawai'i Kai, Kailua and Mililani are being considered for a pilot program, which would be launched in two of those neighborhoods and could expand islandwide if successful.

The City Council is considering a bill that would allow a $10 monthly fee for homes that want to continue having trash picked up twice a week in addition to the recycling pickup. An initial committee vote is expected next month.

Reach Johnny Brannon at jbrannon@honoluluadvertiser.com.