SINGAPORE – Research is under way to determine if the incineration ash from Semakau, Singapore’s only landfill, can be repurposed for other uses, such as building Tuas Port.

As Semakau landfill is expected to reach full capacity by 2035, Minister for Sustainability and the Environment Grace Fu said at the Bloomberg Sustainable Business Summit recently that the Government is mulling over the possibility of recovering the ash for a second lease of life. 

The 350ha landfill, which can hold 28 million cubic m of waste, has two phases. Phase 1 contains 11 landfill cells that are separated by internal bunds, and Phase 2 is 157ha of sea space converted into landfill space. Phase 1 is full, and Singapore has been dumping its waste into Phase 2.

There are mainly three types of waste on the island. Incineration bottom ash makes up the bulk, which is the heavier, solid residues found at the bottom of incineration furnaces; incineration fly ash, which are air pollution control residues; and non-incinerable waste such as wastewater sludge.

The National Environment Agency (NEA) and the Maritime and Port Authority of Singapore are looking into using these waste as an alternative fill material for use in Tuas Port Phase 3.

During the National Day Rally in August 2022, Prime Minister Lee Hsien Loong said that land reclamation work for Tuas Port Phase 2 is in progress and planning for Phase 3 has begun. There are four phases in all, costing a total of $20 billion.

The study, which involves institutes of higher learning and consultants, will evaluate appropriate treatment methods and cost-benefit analyses to determine the viability of mining the landfill.

Assistant Professor Fei Xunchang, from Nanyang Technological University’s School of Civil and Environmental Engineering, told The Straits Times that his research team is currently investigating the various waste residues found in Phase 1 to see if they can be repurposed for other uses, like construction materials.

“The waste there is all mixed together. They have been exposed to rainfall, wind, sunshine for up to 20 years. The quality of the mixed materials is also very different, so the way they behave may also be quite different compared with ash that is produced fresh from the incinerator,” he added.

However, many of these options would require further treatment of the waste to ensure that no contaminants, including heavy metals, end up leaching out, he noted.

This would be of particular concern if the mixed waste was used for land reclamation, as it could be damaging to the marine environment if anything were to leach from it.

ST understands that global engineering consultancy Aecom is currently studying the economic costs of excavating the entire Semakau, but it declined to comment, citing confidentiality.

NEA said the study will continue into 2024, with some preliminary indications on the viability of the project expected by end-2023 or early 2024.