Amendments for short- and medium-term mitigation of odor emissions from dairy manure

Simple and low-cost amendments are popularly used to reduce odor emissions from manure storage and handling. Seven promising products were selected for study after a preliminary screening of 22 dairy manure amendments that represented different modes of action. One feed-through additive was evaluated. Reported results are from manure stored at two temperatures (10 and 20°C) for short- and medium-term periods (3 d and 30 d). Amendment was added to 2-kg dairy manure slurry (1:1.7 feces:urine; 11% total solids) following the manufacturer recommended rates. Two samples of each product were evaluated along with duplicate untreated manure slurry. Odor emissions were estimated by six qualified odor assessors following an international standard method for Triangular Forced-Choice Olfactometry. Odor quality characterizations included hedonic tone (pleasantness), supra-threshold odor intensity, and odor character. None of the amendments significantly reduced odor emissions for all study conditions. There were amendments that demonstrated significant odor reduction under certain conditions: 31 % reduction (P=0.032) for acidic (abandoned) mine drainage sediment after 3 d at 20°C; a proprietary microbial/enzyme powder, a proprietary aerobic/facultative microbial mixture, and proprietary mixture of chemicals in isopropyl alcohol significantly reduced odor by 26 to 47% after 30 d at 20°C Hyssopus and peppermint essential oils increased odor detection by 29 to 65% after 30 d at 10°C but improved odor character descriptors. Odor decreased by 20 to 88% for all treatments and temperatures by simply storing the manure for 30 d. All treatments had unpleasant to extremely unpleasant hedonic tone described as offensive, earthy, medicinal, and fishy. Odor emission was correlated to hedonic tone but more intense odors were perceived as more unpleasant.