“The construction period could be approximately shortened from the original estimate of 72 months to 54 months, a 25 per cent reduction or 18 months ahead of the original estimated schedule,” it said.

“With the construction schedule expedited and various advance work synchronised, they expected that the proposed I·PARK2 could be completed about two years earlier than the original estimated schedule.”

The bureau also suggested including financial incentives in the contract to encourage the contractor to speed up construction.

It said the incentives could be provided through an arrangement for the contractors to share the difference between the actual construction cost and the target cost.

“This can incentivise the client’s representative and the contractor to work in collaboration and formulate the most cost-effective construction method for the smooth implementation of the project and avoidance of budget overrun,” it said.

The other two approaches include studying streamlining work processes as well as learning from major waste incineration enterprises including mainland Chinese ones on enhancing treatment capacity.

I·PARK1, the city’s first waste-to-energy incinerator, is being constructed on an artificial island of about 12 hectares off Shek Kwu Chau. The facility is expected to be commissioned next year and can handle around 3,000 tonnes of waste per day, while reducing volume by 90 per cent after treatment.

Upon full operation, the heat produced by the facility can be used to generate electricity for its daily operation, as well as export an estimated 480 million kilowatt-hours (kWh) of power each year to the grid.

The bureau said I·PARK2’s estimated daily treatment capacity could be increased by 50 per cent from 4,000 to 6,000 tonnes based on studies and views from the industry and contractors.

It added that authorities were considering incorporating community facilities with leisure, recreation and education elements, with sludge treatment facility T·PARK as a reference.

“The spa pools at T·PARK, heated by heat energy recovered from sludge incineration, are well received by the public,” it said.

“In addition to providing an environmental education centre, we are also exploring the possibility for the proposed I·PARK2 to include recreational venues different from those in T·PARK to offer the public a novel recreational experience.”

According to the bureau, some incombustible waste will remain at the bottom of the moving combustion grate and become bottom ash at a size of only 10 per cent of the original volume.

The ash is made up of materials with minimal environmental impact and relatively low recycling value, such as glass and ceramic.

I·PARK2, which has a maximum treatment capacity of 6,000 tonnes per day, was preliminary estimated to generate about 1,200 tonnes of bottom ash each day, it said.

“We will consider setting up bottom ash treatment facilities at the proposed I·PARK2 to treat bottom ash generated from I·PARK1 and the proposed I·PARK2,” it said.

“After treatment, the bottom ash can be used for manufacturing low-carbon green construction materials such as low-carbon cement, non-structural concrete aggregates and road base course aggregates.”

The bureau said this would minimise the amount of the ash disposed at landfills.

Contractors could be invited through the tender documents to propose cost-effective recycling options that catered for the market needs of low-carbon green construction materials, it added.

The bureau also said that I·PARK2, under full operation, could generate 200 tonnes of fly ash each day, which generally had a higher concentration of heavy metals requiring separate treatment.

“According to the experience on the mainland and other regions, the existing technology for recovering fly ash is immature with a high cost,” it said.

“Therefore, we would suggest adopting the prevailing fly ash treatment method by using cement or chemicals for solidification or stabilisation prior to landfill disposal to minimise environmental pollution.”

It said the government would consider recovering fly ash when the technology becomes mature and cost-effective.

Hongkongers disposed on average 1.51kg (3.3 pounds) of waste per day in 2022, official data showed.

Officials have vowed to stop relying on landfills by 2035, with measures such as the waste-charging scheme proposed to hit the target. But the scheme was put aside indefinitely earlier this month after strong public opposition.

Officials earlier said they were also considering investing in incineration and upcycling facilities within the Greater Bay Area to handle part of the city’s waste.

The bay area is a plan to integrate Hong Kong, Macau and nine cities in Guangdong province into an economic and development powerhouse.