Feeding Distiller's Byproducts May Enhance Reduced Sulfur Emissions From Cattle Feedlots.

Reduced sulfur compounds are normal products of manure decomposition which are emitted from confined animal feeding operations (CAFO).  These compounds not only contribute to nuisance odors, but with recent EPA regulations, H₂S emissions in excess of 100 lbs per day must be reported by the livestock operation.  Feeding distiller’s byproducts, which can be very high in sulfur, has recently become very common in large feedlots.  Two studies were conducted to evaluate the relative impact of feeding high sulfur content, wet distiller’s grain plus solubles (WDGS) to beef cattle.  In the first study, beef cattle in sixteen small-scale pens were fed varying amounts (0%, 20%, 40%, and 60%) of WDGS.  Fresh manure composite was collected four times from each pen during the study, and the relative emissions were measured using a laboratory wind tunnel chamber and Jermome meter.  The relative emission of reduced sulfur was significantly greater (4 to 22-fold) in the 40% and 60% WDGS manures for all time periods compared to the 0% manure composite.  A second follow up study in eight production-scale feedlot pens feeding either 0% or 40% WDGS demonstrated that reduced sulfur emissions were consistently larger (up to 2.6-fold) from feedlot surface samples collected near the feed bunk when cattle were fed the 40% diet.  Largest reduced sulfur emissions were detected when the feedlot surface was wet.  Spatially, relative emission from the feedlot surface after animals were removed from the pens came principally from the wetter edges of the pen.  Taken together, the results indicate that very large CAFO need to consider both the sulfur content and the feeding level of WDGS in order to comply with EPA’s reduced sulfur emission guidelines.  More intensive manure management of the edges of pens may minimize emissions, but further research is needed to verify its efficacy.