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Slaughterhouse solid residues treatment using anaerobic digestion

Moukazis Ioannis

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Year 2017
Type of Item Master Thesis
Bibliographic Citation Ioannis Moukazis, "Slaughterhouse solid residues treatment using anaerobic digestion", Master Thesis, School of Environmental Engineering, Technical University of Crete, Chania, Greece, 2017
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The objective of the present study is to evaluate the use of slaughterhouse residues as substrates for anaerobic digestion, aiming at methane production. To this purpose, the biochemical methane potential of slaughterhouse residues of Category 2 and 3, according to European Regulation EC 1069/2009, was initially determined. These assays lasted 30 days and were conducted under mesophilic conditions (35 °C) in batch reactors with nominal volume of 250 mL and working volume of 100 mL. The inoculum used for these assays consisted of anaerobic sludge originating from the anaerobic digesters of the Municipal Wastewater Treatment Plant of Chania. The inoculum was mixed with the substrates, keeping a constant, Substrate/Inoculum Ratio (SIR) equal to 0,25, on volatile solid basis.The above mentioned assays showed that using the sample containing breasts and reproductive organs (SH3), bladders and intestine (SH5) and stomach and rumen (SH1), led to the production of larger methane quantities, yielding 815, 787 and 759 mLCH4STP/gVS, respectively.Subsequently, the applicability of anaerobic co-digestion of the types of slaughterhouse waste which showed higher dynamic biochemical methane potentials, with two agro-residues, particularly orange peel and olive leaves was studied. Anaerobic co-digestion assays were carried out in semi-continuously operated reactors under mesophilic conditions (35°C). The effect of the variation in Organic Loading Rate (OLR) on methane production was investigated.During the experimental procedure, the main characteristics of the collected samples, including total and volatile solids contents, elemental composition, pH, higher calorific value, fiber composition and crude fat content, were also determined.According to the results of the semi-continuous assays, maximum methane yields between 253 - 727 mLCH4/gVSfed were obtained from different waste mixtures, when the feeding took place with an OLR of 0,8 gVS/L/d. Moreover, methane production from the co-digestion of slaughterhouse by-products with orange peels showed better results than the co-digestion with olive leaves. The only case in which methanogenesis inhibition phenomena were observed, due to increased ammonia concentrations, was the assay being fed with a mixture of SH3 and orange peels, at the highest OLR. This inhibition phenomenon was attributed to an inappropriate C/N ratio.

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