NEA is leading the research and development (R&D) efforts to find solutions to extend the lifespan of Semakau Landfill beyond 2035 under the Closing the Waste Loop (CTWL) R&D Initiative
Singapore, 25 September 2020 – The National Environment Agency (NEA) has issued a Request for Proposal (RFP) to study the technical feasibility of recovering mixed landfilled materials. These comprise incineration bottom ash (IBA) and incineration fly ash (IFA) from waste-to-energy (WtE) plants and non-incinerable waste (NIW) from industries, which were landfilled at the Phase I cells of Semakau Landfill. The findings would enable us to better understand how we could extend the lifespan of Semakau Landfill and avoid future costs of constructing another offshore landfill. Besides promoting a circular economy in resource management, the success of this R&D initiative will mark the first step to truly close the waste loop for Singapore, going beyond just recovering NEWSand from treated IBA and Municipal Solid Waste (MSW) slag today.
2 If nothing is done, by 2035, the incineration ash generated from our WtE plants will have nowhere to go, as Semakau Landfill is projected to run out of space by then. Through this RFP, we look forward to exploring innovative and novel solutions for prolonging the lifespan of Semakau Landfill and spur Singapore’s drive towards becoming a zero waste nation.
3 The RFP aims to understand the physical and chemical properties of the landfilled materials comprising IBA, IFA and NIW, that had ‘aged’ over time. The objectives are to assess the technical and economic feasibility of refreshing the landfill space through extracting the landfilled materials and finding suitable applications for the recovered materials, which could potentially be used as sand or aggregate replacement in various applications.
4 Semakau Landfill has been in operation since 1999. Phase I of Semakau Landfill has 11 landfill cells separated by internal bunds. Approximately 15 million tonnes of mixed landfilled materials have been disposed in 10 of the landfill cells. Reducing waste generation is crucial to extending Semakau Landfill’s lifespan beyond 2035. A key waste reduction target in the Zero Waste Masterplan is to reduce the ash and waste sent to Semakau Landfill each day by 30 per cent by 2030 (refer to Annex A for more details on Semakau Landfill and Annex B for photographs of Semakau Landfill). This R&D initiative complements such waste reduction efforts to save Semakau Landfill from being fully filled up.
5 Mr Tan Meng Dui, Chief Executive Officer of NEA said, “We have seen the possibilities of using slag produced from MSW, through a high-temperature gasification process, as a form of NEWSand that has been used to make concrete benches, a footpath in Tampines town and the new concrete plaza in front of the Environment Building. NEA is spearheading R&D 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.”
6 For more information on the RFP, interested proposers may refer to NEA’s website at https://www.nea.gov.sg/programmes-grants/grants-and-awards/closing-the-waste-loop-initiative. Applications will close at 11am on 11 November 2020.
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Factsheet on Semakau Landfill
a. Year Built: 1999 (21 years)
b. Phase I: Opened on 1 April 1999. Landfill capacity of 13.6 million cubic metres.
c. Phase II: Opened on 11 July 2015. Landfill capacity of 14.5 million cubic metres.
d. Location: 8km South of Singapore
e. About Semakau Landfill:
Semakau Landfill was formed by joining two smaller islands – Pulau Semakau and Pulau Sakeng – with a 7km perimeter bund enclosing part of the sea in between. Semakau Landfill is the first man-made offshore landfill in the region that is created entirely out of sea space. The bund is lined with 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. Ancillary facilities like generators, a fire pump house, and a water storage tank were built to ensure that the landfill operation remained self-sustainable.
f. The waste disposal process:
1) Waste that is thrown down the rubbish chute is collected by waste collectors and transported to four waste-to-energy plants – Tuas, Senoko, Tuas South and Keppel Seghers Tuas.
2) The refuse trucks tip their waste load into a bunker where crane operators mix the waste to ensure the composition is homogenous, before feeding the waste into the 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.
3) The flue gas produced during the incineration process is filtered to remove particulates, harmful acidic gases, dioxins and furans, before it is released into the environment through chimneys.
4) Ferrous metal and non-ferrous metal as small as 2mm, like copper and aluminium, are recovered from incineration bottom ash at the metal recovery facility using magnetic and eddy current separators.
5) The remaining ash and non-incinerable waste are transported to Tuas Marine Transfer Station.
6) A tugboat nudges a barge which takes the waste on a 33.3km journey to the Transfer Building at Semakau Landfill.
7) Large excavators with specially designed grabs are used to unload the waste from the barge onto 35-tonne dump trucks.
8) The dump trucks take the incineration ash to the Floating Platform, where it is discharged into the Phase II cell to make uneven seabed shallow and level – a condition that will allow conventional landfilling using bulldozers, excavators and compactors to take place at a later stage of landfilling.
Studies are underway to turn incineration ash into construction material called “NEWSand”. The plan is to use it in non-structural construction such as road base/sub-base materials or aggregates in non-structural concrete.
g. Interesting Facts & Figures:
The size of the mangrove that was replanted to replace those affected by the landfill construction.
The distance that waste travels from Tuas Marine Transfer Station to the Transfer Building at Semakau Landfill.
The number of species of birds that have been spotted on Semakau Landfill and Pulau Semakau, including endangered species.
The size of the entire Semakau Landfill.
The number of colonies of corals that was harvested and transplanted to Sisters’ Island during the development of Phase II.
The year that Semakau Landfill is expected to be filled up.
The amount of waste sent to Semakau Landfill daily. It comprises of 600 tonnes of non-incinerable waste and 1,500 tonnes of incineration ash.
The amount of incineration ash and non-incinerable waste that was sent to Semakau Landfill every year.
28 million cubic metres
The total capacity of waste that Semakau Landfill can hold.
The amount that was spent to complete Phase II in 2015.
The amount that was spent to complete Phase I in 1999.
Photos of Semakau Landfill
(Photo credits: National Environment Agency)
Fig 1. A tugboat and barge berthing at the Transfer Building of Semakau Landfill.
Fig 2. An excavator unloading incineration ash from the barge at the Transfer Building at Semakau Landfill.
Fig 3. A dump truck discharging incineration ash from the Floating Platform at Semakau Landfill.
Fig 4. An aerial view of a dump truck on the Floating Platform at Semakau Landfill.
Fig 5. The floating Wastewater Treatment Plant discharging treated water into the sea at Semakau Landfill.
Fig 6. An aerial view of the Eastern bund of Semakau Landfill.
Fig 7. Phase II Gap closed to form single cell.
Fig 8. An aerial view of replanted mangroves at the Southern plot of Semakau Landfill.