Reduction of H₂S/NH₃ production from pig feces by controlling environmental conditions

The effects of storage temperature and humidity on the malodorous of pig feces was examined in this study. The change of pig feces, including pH, NO₃ ^-, SO₄ ⁼, number of microorganisms, and consumption of oxygen were mearsured under different conditions. The influence of temperature on the emission of ammonia gas and hydrogen sulfide was monitored by gas detector tubes (GASTEC) periodically under seven storage temperatures (10°C, 15°C, 20°C, 25°C, 30°C, 35 °C, and 40°C) and five moisture contents (20%, 40%, 60%, 80%, and 100%). The results showed that the production of NH₃ and H₂S increased up to 175 ppm and 35 ppm respectively when temperature was above 25°C. The effect of humidity on the production of NH₃ and H₂S was depended on storage temperature. The maximum production of NH₃ and H₂S was under 40 % humidity at 40°C . In addition, the decline of NH₃ and H₂S concentration at experimental period were due to physical effect not biological effect because pH decline was caused by H₂S(aq) instead of bioconversion into SO₄ ⁼. The results suggest that the optimal environmental condition to reduce NH₃ and H₂S production as well as the cost of degas equipment was at 25°C and 60% humidity.