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Subject: search.filters.subject.Anaerobic digestion

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    Simulation and optimization of anaerobic co-digestion of food waste with palm oil mill effluent for biogas production
    (2021-12-01)
    Tiong, Jasmine Sie Ming
    ;
    Chan, Yi Jing
    ;
    Lim, Jun Wei
    ;
    Mohamad, Mardawani
    ;
    Ho, Chii Dong
    Food waste (FW) utilized as substrate for anaerobic digestion (AD) to produce biogas is promising. Simultaneously, waste is handled and value-added products such as biogas and fertilizer are produced. Palm oil mill effluent (POME) is used as the co-substrate. This study aims to simulate the complete process flow of anaerobic co-digestion (AcoD), consisting of pre-treatment of feedstock, biogas upgrading, wastewater treatment and sludge dying using SuperPro Designer. Parameters, namely hydraulic retention time (HRT), recycle ratio of sludge, water to FW ratio (kg/kg) and co-substrate to FW ratio (kg/kg), would affect the performance of digester. The optimization of these parameters is performed using Design-Expert software, involving response surface methodology (RSM). The effects on responses such as methane flow, chemical oxygen demand (COD) and volatile solid (VS) removal efficiencies are analyzed. In treating 25,000 kg/h of feed, the optimized values for HRT, recycle ratio, water to feedstock ratio, POME to FW ratio are 37.2 days, 0.381, 0.027 and 0.004, respectively. The methane yield is 0.30 L CH<inf>4</inf>/g of COD removed, with COD and VS removal efficiencies of 81.5% and 68.9%, respectively. The project is profitable, with a payback period of 6.14 years and net present value (NPV) of $5,680,000. A comprehensive understanding of AD matures it for commercialization purposes.
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    Generation and fate of volatile organic sulfur compounds during anaerobic digestion of waste activated sludge
    (2021-01-01)
    Khanthongthip, Passkorn
    ;
    Yagci, Nevin
    ;
    Orhon, Derin
    ;
    Novak, John
    This study investigates the generation and fate of volatile organic sulfur compounds (VOSCs) during biodegradation of waste activated sludge under anaerobic conditions. Experiments involved the operation of laboratory-scale anaerobic digesters at a solid retention time of 20 d. Concentration profiles of methanethiol, dimethyl sulfide (DMS), dimethyl disulfide, and hydrogen sulfide were monitored. Methanethiol (MT) and DMS are the main organic sulfur compounds exhibiting con-secutive increase/decline phases. In the second step, aliquots taken from bioreactors were supple-mented with two sulfur-containing amino acids, cysteine, and methionine. The results suggest that the biodegradation of the two sulfur-containing proteins are the primary source of hydrogen sulfide, methanethiol, and DMS generation. Finally, ethyl-2-butynote was added to aliquots taken from the bioreactors to explore the role of methanogenic activity. Methane production is stopped, and result-ing MT and DMS profiles are no longer included as a declining phase. The results suggest that sulfur amino acids are a potential primary source for the formation of MT and DMS that were subsequently degraded by methanogens. Therefore, reducing proteins containing sulfur amino acids along with increasing methanogenic activity appears to be an effective strategy to control VOSCs and the associated odor problem.
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    Life cycle assessment of MSW-to-energy schemes in Thailand
    (2007-04-13)
    Chaya, Wirawat
    ;
    Gheewala, Shabbir H.
    Life cycle assessment was performed to evaluate environmental impacts of two municipal solid waste (MSW) to energy schemes currently practiced in Thailand: incineration and anaerobic digestion. Potential impacts such as global warming, acidification, stratospheric ozone depletion, and photo-oxidant formation were avoided due to net electricity production and also fertilizer production as by-products from the anaerobic digestion scheme. In addition, the anaerobic digestion resulted in the higher net energy output compared to the incineration scheme. However, the incineration had less potential impact for nutrient enrichment. The LCA results were also useful in determining where the improvements could be made for both the schemes. In order to adopt a sustainable waste management system elsewhere in the country, decision makers may need to consider a combination of techniques, or an integrated method of management. LCA could serve as an invaluable tool for such an analysis. © 2006 Elsevier Ltd. All rights reserved.