Parliament Q&A

Written reply by Ms Grace Fu, Minister for Sustainability and the Environment, to Parliamentary Question on Research into Incineration Ash and Non-Incinerable Waste, on 6 October 2020

Mr Christopher de Souza: To ask the Minister for Sustainability and the Environment whether research is being conducted to consider possible sustainable uses for incinerated ash and non-incinerable waste.


1. The National Environment Agency (NEA) has been studying different ways to convert incineration bottom ash (IBA) into construction material, which we call NEWSand. This involves treatment methods such as washing and chemical stabilisation, after the removal of metals from the IBA. NEA is planning field trials using NEWSand from treated IBA for road construction at Tanah Merah Coast Road. 

2. NEA is also piloting the use of slagging gasification technology at the Nanyang Technological University (NTU) Waste-to-Energy Research Facility to directly convert municipal solid waste into glass-like slag, which can be used directly as NEWSand. For example, NEA has successfully used NEWSand from the slag to construct the concrete plaza in front of the Environment Building. 

3. These efforts to create NEWSand, if successfully scaled up, will create a sustainable source of construction materials while helping to prolong the lifespan of Semakau Landfill. 

4. NEA partners Institutes of Higher Learning, research institutes and the private sector to improve treatment methods for IBA, as well as develop new uses for incineration ash. For example, Republic Polytechnic is working on developing cost-effective techniques to treat and convert incineration ash into aggregates. NTU is also researching the use of incineration ash in automotive catalytic converters. 

5. Non-incinerable waste (NIW), which includes industrial sludges and asbestos, makes up about 30% of waste sent to Semakau Landfill by weight. We are exploring new technologies to reduce NIW. For example, PUB is piloting a thermal hydrolysis process that reduces the amount of sludge from used water treatment. To spur further research, NEA launched a Request for Proposal (RFP) in March 2020 to call for research projects to recycle or reduce NIW. The RFP closed in July 2020, with 22 proposals received. These proposals are currently under evaluation.

6. My Ministry will continue to work closely with stakeholders to leverage science and technology to address incineration ash and NIW, supported by NEA’s $45 million Closing the Waste Loop R&D Initiative. This is part of our strategy to reduce the amount of waste sent to landfill by 30% by 2030 under the Zero Waste Masterplan.

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