Reduction of odor and volatile substances in pig slurries by using pit additives

The effects of five commercial pit additive products on the release of odor nuisance and volatile compounds from swine manure were examined in this study. The changes of pH, volatile fatty acids, total solids, total volatile solids, total nitrogen, and total ammonia nitrogen in swine manure were measured and the levels of aerial ammonia and hydrogen sulfide were monitored. The odor threshold was determined by a dynamic triangle forced-choice olfactometer. The results showed that all the five products reduced the levels of odor threshold by different degrees ranging from 58% to 87% as compared with the control samples. Three of the five products showed reductions in volatile fatty acids and total volatile solids. Comparing the reduction in odor threshold levels with the changes in the amount of volatile fatty acids indicated that the malodor intensities are not proportionally related to the overall amount of volatile fatty acids existing in the swine manure. The malodor could be produced by certain types of volatile fatty acids which are not necessarily present in high concentrations. The abatement of ammonia emission from swine manure were not determined in this study due to low pH values for both the treated and the control samples.