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The fabrication of conductive carbon nanomaterial has attracted extensive research due to its promising potential in energy application. However, the conventional fabrication methods, e.g. chemical vapour deposition, are expensive due to high energy consumption, which makes it both economically and environmentally unsustainable. The concept of using carbonaceous waste as a precursor for growing carbon nanomaterial has recently been explored. By using carbonaceous waste, the fabrication of conductive carbon will be more sustainable. In this work, a carbonaceous waste has the potential to be a precursor for the fabrication of conductive carbon nanomaterial. Our previous characterisation work showed that the carbonaceous waste had a nano-particle size distribution and possessed conductive property. Due to its inherent nano-particle size, no further size reduction is required. However, the carbonaceous waste had to be leached to remove the toxic heavy metal. After leaching, the conductive property decreased slightly. This work explores the use of hydrothermal treatment of the leached sample at low temperature to modify the surface area and surface functional groups, so as to enhance the conductive property of the carbonaceous waste. The capacitance of the treated carbonaceous residue was also analysed.

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.

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 investigated the influence of moisture content and temperature on the degree of carbonation of municipal solid waste (MSW) incineration bottom ash (IBA) from two different incineration plants in Singapore. The initial rate of carbonation was affected by the nominal moisture content used. Carbonation temperature seemed to play a part in changing the actual moisture content of IBA during carbonation, which in turn affected the degree of carbonation. Results showed that 2 h of carbonation was sufficient for the samples to reach a relatively high degree of carbonation that was close to the degree of carbonation observed after 1 week of carbonation. Both Cu and Cr leaching also showed significant reduction after only 2 h of carbonation. Therefore, the optimum moisture content and temperature were selected based on 2 h of carbonation. The optimum moisture content was 15% for both incineration plants while the optimum temperature was different for the two incineration plants, at 35 °C and 50 °C. The effect on Cu and Cr leaching from IBA after accelerated carbonation was evaluated as a function of carbonation time. Correlation coefficient, Pearson’s R, was used to determine the dominant leaching mechanism. The reduction in Cu leaching was found to be contributed by both formation of carbonate mineral and reduction of DOC leaching. On the other hand, Cr leaching seemed to be dominantly controlled by pH. Accepted version

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.