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The management of solid waste has become increasingly challenging with the accelerated growth in residency in Singapore. Alternative utilization, such as high temperature thermal energy storage material, valorizes the waste to the status of a new resource, thereby reducing the need of virgin material and ensuring sustainability. In Singapore, coal is co-fired with biomass and the coal/biomass fly ash is partially reused and the rest is landfilled. This research evaluated two different fabrication routes: conventional sintering and plasma processing. The novelty of this study is that unlike most studies whereby plasma arc is used to melt the ash at high temperature, in this study, a 13.56 MHz radio frequency plasma is used to control discharge parameters through in-situ diagnostics of active species density and temperatures. This allows for high throughput and uniform processing. An optimized plasma process could potentially reduce the total number of processing phases, with a lower energy budget for processing, while increasing the controllability of the processes to achieve the desired material properties. The chemical composition, and the thermal properties such as specific heat capacity, energy density and thermal conductivity of the ceramics made from coal/biomass fly ash were evaluated. Experimental evaluation shows that the radio frequency plasma processed coal/biomass fly ash samples were found to improve the thermal properties of coal/biomass fly ash in general. It is hypothesized that the mechanism of improvement from radio frequency plasma was due to the incorporation of hydrogen into the material and the conversion of mineralogical composition (i.e. quartz) which gave rise to the better performance. In conclusion, this study has shown the potential of using coal/biomass fly ash as thermal energy storage material through innovative process such as radio frequency plasma discharge.

Incineration is one of the methods in providing an efficient management of the municipal solid waste problem. At the same time, the energy released during the combustion of the waste can be harnessed for heat and generation of electricity. While there is potential for improved harnessing of electricity, the high chloride and sulphate content found in the waste limited the steam temperature to the current 400°C due to corrosion issues. Another limiting factor is the fluctuation in the gas temperature, which resulted in an unstable supply of heat to the heat exchangers. This paper briefly reviews the corrosion mechanism and the issues related to the temperature fluctuation from the combustion. This paper also discusses the current and new technologies used to overcome the corrosion attack on the ferrous surface and the temperature fluctuation.

Accelerated carbonation has been studied as a treatment method for MSW IBA, and the main advantage is that it can shorten the treatment duration from months to days, compared to natural weathering. This study investigated the effect of accelerated carbonation on different size fractions of IBA collected from two incineration plants in Singapore. The different size fractions were ground to

This study evaluated the potential of utilising sewage sludge incineration ash as a land reclamation material. Toxicity assessment of the leachate of the ash was carried out for both terrestrial and marine organisms. Both the fruit fly Drosophila melanogaster and barnacle Amphibalanus amphitrite showed that both bottom and fly ash leached at liquid-to-solid (L/S) ratio 5 did not substantially affect viabilities. The leachate carried out at L/S 10 was compared to the European Waste Acceptance Criteria and the sewage sludge ashes could be classified as non-hazardous waste. The geotechnical properties of the sewage sludge ash were studied and compared to sand, a conventional land reclamation material, for further evaluation of its potential as a land reclamation material. It was found from direct shear test that both bottom and fly ashes displayed similar and comparable shear strength to that of typical compacted sandy soil based on the range of internal friction angle obtained. However, the consolidation profile of bottom ash was significantly different from sand, while that of fly ash was more similar to sand. Our study showed that the sewage sludge ash has the potential to be used as a land reclamation material.

Environmental issues are often neglected until a lapse in the care for environment, which leads to serious human health problem, would then put regulation gaps in the spotlight. Environmental regulations and standards are important as they maintain balance among competing resources and help protect human health and the environment. One important environmental standard is related to municipal solid waste (MSW). Proper MSW management is crucial for urban public health. Meanwhile, the sustainability of landfills is also of concern as increasing volumes of MSW consume finite landfill space. The incineration of MSW and the reuse of incinerated residues help alleviate the burden on landfill space. However, the reuse of MSW incinerator residues must be regulated because they may expose the environment to toxic heavy metal elements. The study of environmental standards from different countries applicable to MSW is not widely published, much less those for incinerated MSW residue reuse. This paper compares extant waste classification and reuse standards pertinent to MSW, and explores the unique recent history and policy evolution in some countries exhibiting high environmental regard and rapid changes, so that policy makers can propose new or revise current MSW standards in other countries.