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Author: search.filters.author.Daud, Hanita

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    Anaerobic Co-Digestion of Food Waste with Sewage Sludge: Simulation and Optimization for Maximum Biogas Production
    (2022-04-01)
    Cheong, Wai Lin
    ;
    Chan, Yi Jing
    ;
    Tiong, Timm Joyce
    ;
    Chong, Woon Chan
    ;
    Kiatkittipong, Worapon
    Anaerobic co-digestion (ACD), where two or more substrates are digested simultaneously, is able to prevent the problems associated with mono-digestion. The aim of this study is to develop a simulation model of ACD of food waste (FW) with sewage sludge (SS) for biogas production coupled with pre-treatment, sludge handling and biogas upgrading using SuperPro Designer v9.0. The Design Expert v13 is employed to perform optimization and evaluate the effect of hydraulic retention time (HRT), sludge recycle ratio, water to feed ratio (kg/kg) and SS to FW ratio (kg/kg) on the methane flow, chemical oxygen demand (COD) and volatile solids (VS). The results show that the methane yield of 0.29 L CH4/g COD removed, COD removal efficiency of 81.5% and VS removal efficiency of 69.2% are obtained with a HRT of 38.8 days, water to feed ratio (kg/kg) of 0.048, sludge recycle ratio of 0.438 and SS to FW ratio (kg/kg) of 0.044. Economic analysis has shown this study is feasible with a payback time of 6.2 years, net present value (NPV) of $5,283,000 and internal return rate (IRR) of 10.2%. This indicates that the ACD of FW and SS is economically feasible in a larger scale.
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    Rhizopus oligosporus-assisted valorization of coconut endosperm waste by black soldier fly larvae for simultaneous protein and lipid to biodiesel production
    (2021-02-01)
    Wong, Chung Yiin
    ;
    Kiatkittipong, Kunlanan
    ;
    Kiatkittipong, Worapon
    ;
    Lim, Jun Wei
    ;
    Lam, Man Kee
    Coconut endosperm waste (CEW) was treated by Rhizopus oligosporus via in situ and ex situ fermentations together with bioconversion into valuable black soldier fly larval biomass. The ex situ fermentation could overall enrich the nutritional compositions of CEW by hydrolyzing its complex organic polymers and exuding assimilable nutrients to enhance the black soldier fly larvae (BSFL) growth. Nevertheless, the larval gut bacteria were competing with Rhizopus oligosporus in in situ fermentation, derailing the hydrolysis processes and larval growth. Accordingly, the highest growth rates achieved were around 0.095 g/day, as opposed to only 0.065 g/day whilst using 0.5 wt% of Rhizopus oligosporus to perform ex situ and in situ fermentations, respectively. These were also underpinned by the greater amount of total CEW consumed when employing ex situ fermentation, with comparable metabolic costs to feeding on in situ-fermented CEW. The mature BSFL were subsequently harvested and the amounts of protein and lipid produced were assessed in terms of their feasibility for biodiesel production. While the statistical analyses showed that the larval protein yields derived from both fermentation modes were insignificant, the BSFL could attain higher lipid and protein productivities upon feeding with ex situ-rather than in situ-fermented CEW mediums. Better yet, the larval biodiesel quality measured in terms of the fatty acid methyl ester composition were not varied significantly by Rhizopus oligosporus through the fermentation process. Thereby, the presence of 1.0 wt% Rhizopus oligosporus was considered optimum to perform ex situ fermentation, giving rise to the acceptable growth of BSFL loaded with the highest lipid yield and productivity for producing biodiesel and protein simultaneously.