Turning trash into treasure: NEA to reuse landfill material

Effort will extend life of Semakau Landfill, which is filling fast, and lifespan of wastes

An aerial view of the Eastern bund of Semakau Landfill. NEA is seeking innovative solutions for prolonging the lifespan of the landfill and spurring Singapore's drive towards becoming a zero waste nation.
An aerial view of the Eastern bund of Semakau Landfill. NEA is seeking innovative solutions for prolonging the lifespan of the landfill and spurring Singapore's drive towards becoming a zero waste nation.PHOTO: NATIONAL ENVIRONMENT AGENCY
A dump truck discharging incineration ash from the Floating Platform at Semakau Landfill. A tugboat and barge berthed at Semakau Landfill.
A tugboat and barge berthed at Semakau Landfill.PHOTOS: NEA
A dump truck discharging incineration ash from the Floating Platform at Semakau Landfill. A tugboat and barge berthed at Semakau Landfill.
A dump truck discharging incineration ash from the Floating Platform at Semakau Landfill.PHOTOS: NEA

The National Environment Agency (NEA) is looking to reuse landfill materials in an effort to turn trash to treasure.

This would not only extend the lifespan of ash and other wastes but also the life of Semakau Landfill, which is fast filling up.

Singapore's one and only landfill has been in operation since 1999. It is projected to run out of space by 2035 if no action is taken, NEA said in a statement yesterday.

To better understand how the lifespan of Semakau Landfill can be extended and how to avoid having to construct another offshore landfill, NEA has issued a proposal to study the technical feasibility of recovering mixed landfilled materials.

This would also help promote a circular economy with zero waste.

These mixed landfilled materials comprise incineration bottom ash (IBA) and incineration fly ash, which come from waste-to-energy plants, as well as non-incinerable waste from industries. IBA is the thicker and heavier component of incineration ash.

If successful, this initiative will mark the first step to truly close the waste loop for Singapore by creating NEWSand, which is generated from IBA and municipal solid waste slag.

NEWSand has been used in the past to make concrete benches, a footpath in Tampines town and the new concrete plaza in front of NEA's Environment Building.

Through this proposal, NEA seeks to explore innovative and novel solutions for prolonging the lifespan of Semakau Landfill as well as spur Singapore's drive towards becoming a zero waste nation, the agency said.

The proposal aims to understand the physical and chemical properties of the landfilled materials that had "aged" over time.

By assessing the technical and economic feasibility of extracting the landfilled materials and applying them elsewhere, such as potentially using them as sand, the landfill space could be refreshed.

  • Where the trash goes and what next

  • SEMAKAU LANDFILL LIES JUST 8KM SOUTH OF SINGAPORE 

    It is the first man-made offshore landfill in the region created entirely out of sea space. The landfill was built in 1999 and has been in continuous operation ever since. It was formed by joining two smaller islands - Pulau Semakau and Pulau Sakeng - with a 7km perimeter bund enclosing part of the sea in between.

    The bund is lined with an impermeable membrane and a layer of marine clay, ensuring that leachate from the waste is contained within the landfill and does not pollute the sea.

    The first phase of the landfill was opened on April 1, 1999, with a capacity of 13.6 million cubic metres. The second phase opened on July 11, 2015 with a capacity of 14.5 million cubic metres.

  • HOW IS OUR TRASH DISPOSED?

    • Waste that is thrown down the rubbish chute is collected by waste collectors and transported to one of four waste-to-energy plants: Tuas, Senoko, Tuas South and Keppel Seghers Tuas.

    • The waste is mixed to ensure a homogeneous composition before it is fed to incinerators. The incineration process reduces the volume of waste by up to 90 per cent. The heat produced is harnessed to produce electricity, which is fed into the national grid.

    • The flue gas produced in the process is filtered before it is released into the environment.

    • Ferrous and non-ferrous metals as small as 2mm, such as copper and aluminium, are recovered from incineration ash.

    • The remaining ash and non-incinerable waste are transported to Tuas Marine transfer station.

    • A tugboat takes the waste on a 33.3km journey to the transfer building at Semakau Landfill.

    • Large excavators are used to unload the waste onto 35-tonne dump trucks.

    • Dump trucks carrying incineration ash go to the Floating Platform for direct discharges of ash into the deeper end of the landfill cells or for conventional landfilling involving bulldozer and compactor.

    Clara Chong

A key waste reduction target in Singapore's Zero Waste Masterplan is to reduce by a third the ash and waste sent to Semakau Landfill each day by 2030. This initiative would complement current waste reduction efforts to save Semakau Landfill from being fully filled up.

Mr Tan Meng Dui, chief executive of NEA, said: "NEA is spearheading research and development efforts to go even further, so as to truly close the waste loop for the range of end-of-life waste and residues ending up at Semakau Landfill.

"This R&D initiative seeks to develop safe and sustainable solutions to turn the trash dumped into a landfill, into treasure that will have new future uses."

A version of this article appeared in the print edition of The Straits Times on September 26, 2020, with the headline 'Turning trash into treasure: NEA to reuse landfill material'. Print Edition | Subscribe