ANAEROBIC DIGESTION OF SWINE MANURE: INHIBITION BY AMMONIA

• Published in: Water research (Oxford) 1998, Vol.32 (1), p.5-12
• Main Authors: HANSEN, KAARE HVID, ANGELIDAKI, IRINI, AHRING, BIRGITTE KIÆR
• Format: Article
• Language: English
• Subjects: Agriculture, rearing and food industries wastes; ammonia; ammonia inhibition; anaerobic degradation; anaerobic digestion; Applied sciences; biogas; Biological and medical sciences; Biological treatment of sewage sludges and wastes; Biotechnology; Environment and pollution; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Industrial applications and implications. Economical aspects; inhibition; mathematics and statistics; methane; methane production; pig manure; Pollution; swine manure; temperature; Wastes
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/S0043-1354(97)00201-7

A stable anaerobic degradation of swine manure with ammonia concentration of 6 g-N/litre was obtained in continuously stirred tank reactors with a hydraulic retention time of 15 days, at four different temperatures. Methane yields of 188, 141, 67 and 22 ml-CH 4/g-VS were obtained at 37, 45, 55 and 60°C, respectively. The yields were significantly lower than the potential biogas yield of the swine manure used (300 ml-CH 4/g-VS). A free ammonia concentration of 1.1 g-N/litre or more was found to cause inhibition in batch cultures at pH 8.0 (reactor pH), and higher free ammonia concentrations resulted in a decreased apparent specific growth rate. Batch experiments with various mixtures of swine and cattle manure showed that the biogas process was inhibited when the swine-to-cattle manure ratio was higher than 25:75, corresponding to a free ammonia concentration of approximately 1.1 g-N/litre. Inhibition of the biogas process and, thereby, a reduction of the methane yield followed a four-stage pattern: below a threshold of 1.1 g-N/litre free ammonia, the process was uninhibited; over this concentration, inhibition occurred, forming first a phase with an initial inhibition, then a plateau and then an inhibition stage where the apparent specific growth rate decreased with increasing concentrations of free ammonia. © 1998 Elsevier Science Ltd. All rights reserved