Investigation of Biogas Production by Co-Digestion of Brewery Wastewater and Brewery Spent Yeast

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Addis Ababa University


Production of biogas through anaerobic digestion of organic waste materials provides an alternative environmentally friendly renewable energy. In this study, biogas production from codigestion of brewery wastewater, spent yeast and brewery sludge in five mix ratios was evaluated under mesophilic condition (35 ℃, 37 ℃, 39 ℃) using a batch digester for 21 days. For all substrates, total solids (TS), biological oxygen demand (BOD), chemical oxygen demand (COD), temperature (T), total nitrogen (TN), total phosphorus (TP), and pH were measured before and after digestion. For the experimental design, different mix ratios of yeast and wastewater by volume (0 %, 1 %, 6 %, 11 %, 100 %) were adopted for all the anaerobic digestion employed. All measured physico-chemical parameters of the sample substrate significantly varied before and after anaerobic digestion AD. Gas production was measured for all the samples periodically starting from fourth day of digestion experiment and went to zero at about 21 days in all substrates. Assessment of cumulative biogas production revealed that substrate in a mix ratio of 1 %, temperature 37 ℃, pH 6.5 (3417 mL/800 mL sample) spent and 6 %, 37 ℃, 6.5 (3325.5 mL/800 mL sample) showed the highest biogas production and the lowest was in 11 % volume ratio, 35 ℃ temperature and pH of 5 (2173 mL/800 mL sample) and 11 %, 39 ℃, 5 pH suggesting the first mix ratio of the two substrates is an optimal mix to yield better biogas. Overall the results indicated that biogas yield and TS, BOD, COD reduction can be significantly enhanced when brewery spent yeast and brewery wastewater are co-digested.



Biogas, Co-digestion, anaerobic digestion, BOD, COD, TS, TN, TP, spent yeast