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 measured 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 degrees C, 15 degrees C, 20 degrees C, 25 degrees C, 30 degrees C, 35 degrees C, and 40 degrees 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 degrees 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 degrees 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 degrees C and 60% humidity.