Effect of waste cooking oil addition on ammonia emissions during the composting of dairy cattle manure

Abstract

Objective: The objective of this study was to evaluate the effect of waste cooking oil (WCO) addition on ammonia (NH3) emissions during the composting of dairy cattle manure under two aeration conditions. Methods: The composting tests were conducted using the laboratory-scale composting apparatuses (14 L of inner volume). Three composting treatments (Control, WCO1.5, and WCO3, with WCO added at 0 wt%, 1.5 wt%, and 3 wt% of manure, respectively) were performed in two composting tests: aeration rate during composting was changed from 0.55 to 0.45 L/min in Test 1, and fixed at 0.3 L/min in Test 2, respectively. The NH3 emitted and nitrogen losses during the composting were analyzed, and the effect of the addition of WCO on NH3 emissions were evaluated. Results: Both tests indicated that the composting mixture temperature increased while the weight and water content decreased with increasing WCO content of the composting mixtures. On the other hand, the NH3 emissions and nitrogen loss trends observed during composting in Tests 1 and 2 were different from each other. In Test 1, NH3 emissions and nitrogen losses during composting increased with increasing WCO contents of the composting samples. Conversely, in Test 2, they decreased as the WCO contents of the samples increased. Conclusion: The WCO addition showed different effect on NH3 emissions during composting under two aeration conditions: the increase in WCO addition ratio increased the emissions under the higher aeration rate in Test 1, and it decreased the emissions under the lower aeration rate in Test 2. To obtain reduction of NH3 emissions by adding WCO with the addition ratio ≤3 wt% of the manure, aeration should be considered.