Mitigation of nitrogen losses with Australian zeolites during the anaerobic digestion of swine manure

Thushari N. Wijesinghe1, Kithsiri B. Dassanayake2, Peter J. Scales2, Deli Chen1

1 Faculty of veterinary and Agriculture Sciences, The University of Melbourne, Parkville, Victoria, 3110 [email protected]

2 School of Engineering, The University of Melbourne, Parkville, Victoria, 3010

Abstract

Anaerobic digestion (AD) is one of the most effective and sustainable methods of handling swine manure that convert organic wastes into a greener energy, effectively reducing methane (CH4) and ammonia (NH3) emissions. Production of higher levels of total ammonia-nitrogen (TAN) during the acidogenesis due to the high nitrogen (N) contents in swine manures significantly reduce the CH4 yield. Australian zeolites have a high adsorption capacity of ammonium (NH4+).Therefore; reduction of N during the AD through zeolite not only improves the CH4 production but also reduces potential environmental risks associated with NH3 emissions from swine manure. This study is aimed at determining the optimum Australian zeolite dose that produces maximum TAN recovery at optimum CH4 production. Swine manure was treated with natural and sodium zeolites at 0, 10, 40, 70, 100mg/L and digested anaerobically for 60 days.  Natural zeolites at a dose of 40g/L resulted in the highest increase (29%) in total CH4 yield from swine manure compared to the untreated manures, while natural and sodium zeolites at a dose of 100g/L reduced 50% and 52% of NH4+ in the medium respectively, compared to the control. However, the increases in CH4 yield under those two treatments were only 10% and 12%.