EFFECTS OF MANURE REMOVAL STRATEGIES ON ODOR AND GAS EMISSIONS FROM SWINE FINISHING

Abstract

Odor, ammonia (NH3) and hydrogen sulfide (H2S) concentrations, and emission rates were measured in two small rooms of finishing pigs with various manure removal strategies. The strategies included daily flush, and static pits with 7, 14, and 42 d manure accumulation cycles, with and without pit recharge with some secondary lagoon effluent after emptying. In each room, tests were conducted with three successive groups of 25 pigs, which were fed standard corn-soybean diets. Ammonia and H2S concentrations were measured automatically 15 to 24 times daily at various locations with chemiluminescence and pulsed fluorescence analyzers, respectively. Odor concentration, intensity, and hedonic tone of air samples were evaluated by a panel of eight trained subjects. Flushing and static pit recharge with lagoon effluent resulted in significantly less NH3, H2S, and odor emissions (P < 0.05). Draining static pits more frequently also significantly reduced H2S and odor emissions. Geometric mean odor emission rates were 19, 33, and 29 OUE s-1 AU-1 (OUE = European odor unit equivalent to 123 .g n-butanol, AU = 500 kg live mass) for the 1 d (daily flush), 7 d, and 14 d cycles without pit recharge, respectively, and 2.6 and 25 OUE s-1 AU-1 for the 7 d and 42 d cycles with pit recharge, respectively. Mean NH3 emission rates were 15, 27, and 25 g d-1 AU-1 for the 1, 7, and 14 d cycles without pit recharge, and 10, 12 and 11 g d-1 AU-1 for the 7, 14, and 42 d cycles with pit recharge, respectively. Mean H2S emission rates were 0.11, 0.27, and 0.41 g d-1 AU-1 for the 1, 7, and 14 d cycles without pit recharge, and 0.16, 0.34, and 1.42 g d-1 AU-1 for the 7, 14, and 42 d cycles with pit recharge, respectively. The mean H2S emission rate during daily flushing was 0.40 g d-1 AU-1 when flushing-induced burst emissions were included in the means, as compared with 0.11 g d-1 AU-1 when flushing times were excluded. Sudden emissions during flushing events had a significant influence on mean emissions from these relatively small rooms; however, without valid data from week 1, the mean H2S emission rate of 0.40 g d-1 AU-1 was probably an overestimate. Daily flushing reduced odor emissions by 41% and 34% (P < 0.05) as compared with the 7 d and 14 d cycles, respectively. The 7 d cycle resulted in 35% and 53% lower H2S emissions as compared with the 14 d cycle with and without pit recharge, respectively. The 14 d cycle had 76% less (P < 0.05) H2S emission than the 42 d cycle, both cycles with pit recharge. Mean daily NH3 emissions from the rooms with static pits were 51% to 62% lower (P < 0.05) with recharge than without recharge. Similarly, mean daily H2S emissions were 18% to 40% lower with pit recharge. In summary, lower NH3 and H2S emissions occurred when pits were recharged after emptying, and when pits were emptied more frequently.