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A COMPARATIVE ENERGY BALANCE MODEL OF THE ANAEROBIC DIGESTION OF DOMESTIC FOOD WASTE BOTH WITH AND WITHOUT DOMESTIC SEWAGE SLUDGE

Bajzelj, Bojana (2009) A COMPARATIVE ENERGY BALANCE MODEL OF THE ANAEROBIC DIGESTION OF DOMESTIC FOOD WASTE BOTH WITH AND WITHOUT DOMESTIC SEWAGE SLUDGE. Masters thesis, Imperial College London.

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    Abstract

    This study models biogas yields from anaerobic digestion using Anaerobic Digestion Model 1 (ADM1), focusing on the effects the carbohydrates, proteins and lipids content in domestic food waste has on biogas yields. The model was adapted to accept varying feedstock compositions as this is seen as one of the most important differences between food waste and sewage sludge that could be the cause of digester failures.

    Mixed co-digestion simulations achieved slightly better yields and greater stability compared to separate digestion. Pure or high food waste mixtures were only digested successfully in simulation with a high cation content, whereas lower mixtures proved to be successful in all conditions. Methane yields per volatile solids added were roughly 480 m3/tonne in most mixtures; however the yields per digester volume ranged from 1 m3/m3 with pure sewage sludge to 5.3 m3/m3 with pure food waste. Simulations suggested sewage treatment works could almost double their biogas production by mixing 15% food waste, based on volume, to their sewage sludge, without compromising the stability of the digester. At higher hydraulic retention times or lower variability, higher volumes of food waste could be co-digested.

    Results from simulations were comparable to values published in literature – the model gave only slightly higher yields and achieved digestion with somewhat higher organic loading rates than is believed possible. The outcomes of the model were highly sensitive to the magnitude of variation and the cation content of the feedstock. Results should be taken with caution, as they assume ideal conditions. Exact figures depend on a variety of parameters, many of which are either completely unknown, such as cation content, or not exact, such as variability and chemical composition. Better characterization of food waste is crucial for improving understanding of anaerobic digestion outcomes. Quantifying the uncertainties in the variability of composition models, such as ADM1, could increase the accuracy of digester stability predictions and offer firm indications of the necessary measures for optimal use of the resultant biogas.

    Aims and Objectives

    UNSPECIFIED

    Headline Findings

    UNSPECIFIED
    Item Type: Thesis (Masters)
    Collections: Defra/CIWM Sponsored Master's Theses > 2009
    Organisation Type: Academic
    Country: Europe > European Union (EU) > United Kingdom
    Topics: Waste And Resources Topics > Waste Technologies > Mechanical Biological Treatment (MBT) > Biological Treatment > Anaerobic Treatment
    Waste And Resources Topics > Waste Sources > Municipal Waste > Domestic Waste
    Waste And Resources Topics > Waste Materials > Sewage sludge
    Depositing User: Users 9 not found.
    Date Deposited: 19 Oct 2010 12:14
    Last Modified: 27 Jun 2012 15:25
    URI: http://warrr.org/id/eprint/776

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