Preliminary investigation of air bubbling and dietary sulfur reduction to mitigate hydrogen sulfide and odor from swine waste

When livestock manure slurry is agitated, the sudden release of hydrogen sulfide (H2S) can raise concentrations to dangerous levels. Low-level air bubbling and dietary S reduction were evaluated as methods for reducing peak H2S emissions from swine (Sus scrofa) manure slurry samples. In a first experiment, 15-L slurry samples were stored in bench-scale digesters and continuously bubbled with air at 0 (control), 5, or 10 mL min(-1) for 28 d. The 5-L headspace of each digester was also continuously ventilated at 40 mL min(-1) and the mean H2S concentration in the outlet air was < 10 mu L L-1. On Day 28, the slurry was agitated suddenly. The peak H2S concentration exceeded instrument range (> 120 mu L L-1) from the control treatment, and was 47 and 3.4 mu L L-1 for the 5 and 10 mL min(-1) treatments, respectively. In a second experiment, individually penned barrows were fed rations with dietary S concentrations of 0.34,0.24, and 0.15% (w/w). Slurry derived from each diet was bubbled with air in benchscale digesters, as before, at 10 mL min(-1) for 12 d and the mean H2S concentration in the digester outlet air was 11 mu L L-1. On Day 12, the slurry was agitated but the H2S emissions did not change significantly. Both low-level bubbling of air through slurry and dietary S reduction appear to be viable methods for reducing peak H2S emissions; from swine manure slurry at a bench scale, but these approaches must be validated at larger scales.