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Title: Enhancement of Biogas Production Using Chemical and Thermal Pre-Treatments in The Anaerobic Co-Digestion of Cow Dung and Poultry Litter in Batch Fermentation
Authors: Animut Assefa
Meseret Chimdessa
Keywords: Anaerobic Digestion, Biogas, chemical pre-treatment, Co-Digestion, Low temperature pre-treatment, Total solids, Volatile solids
Issue Date: Nov-2013
Publisher: Haramaya University
Abstract: Low degradability of substrates is one of the factors that hinder the production of biogas. With the aim of maximizing biogas yields from wet co-digestion of CD and PL, a series of experiments were carried out under mesophilic conditions at 38 ºC using batch digester operating for 21 days hydraulic retention time (HRT). Anaerobic degradability test with mix of 5 different proportions were carried out to obtain suitable mix ratio for maximum biogas production from co-digestion of CD with PL having 8% TS. Having determined the optimum mix ratio, chemical pre-treatment with NaOH (0.45 g, 1.35 g and 2.25 g) and low temperature pre-treatment at 60 and 80 ºC were applied to compare the results with those obtained with non-pre-treated waste. The cumulative biogas yield of 75%CD+25%PL digestion was found to be 2.17 times higher than that of 100% CD and 0.29 times higher than that of 100% PL. Increasing the proportion of PL above 25% decreased the amount of gas production, volatile solids (VS) and total solids (TS) reduction. Thus 75%CD+25%PL mix was found to be optimum mix ratio to result in high biogas yield. Cumulative biogas production and VS reduction from anaerobic digestion of 80 ºC pre-treated substrate was 46.3% and 26.1% higher than the control, respectively. However, thermal pre-treatment at 60 and 80 ºC did not show statistically significant difference in biogas production (p<0.05). Biogas yield of substrates that received 0.45 g, 1.35 g, and 2.25 g of NaOH increased biogas production by 0.03%, 21% and 56% over that of the control, respectively. Overall the results indicated that the biogas yield and VS and TS reduction of a 75%CD+25%PL mix can be enhanced under thermal and chemical pre-treatments prior to anaerobic digestion.
Appears in Collections:Biology

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