Swine manure storage covers for odor control

Twenty-one, 750-L (200 gal) polyethylene tanks were filled with swine manure. Air samples were collected 24 and 48 h after each manure addition. The samples were tested for odor strength using a dynamic olfactometer and for hydrogen sulfide concentration using a Jerome meter. The experimental design consisted of a randomized block design containing three blocks (replications) of seven treatments. The seven treatments included no cover (control), straw mat, vegetable oil mat, straw/oil mat, clay ball mat, PVC/rubber membrane, and geotextile membrane. Statistical analysis indicated that all three main effects - cover treatment, collection period, and time after manure addition - significantly (5% level) affected odor units and hydrogen sulfide concentration. Considering all air collections, the six covers reduced odor units and hydrogen sulfide concentration at various points in the study, but not in a consistent manner. The straw mat and PVC/rubber membrane significantly reduced both odors units and hydrogen sulfide concentration consistently 24 h after manure addition during the first three collection periods. Mixing vegetable oil with straw appears to increase longevity of the cover as compared to straw only. The vegetable oil layer, when mixed with the manure, produced a distinctively offensive non-swine odor. The clay ball mat reduced emissions, although not as well as other covers. A geotextile membrane may be a possible cover choice, since the fabric is self-floating and the biofilm that grew on the mat could self-seal the cover. A straw mat (possibly including vegetable oil) and PVC/rubber membrane appear to be the most effective covers in reducing both odors and hydrogen sulfide. Oil alone should not be used as a cover.