Submitted to: International Symposium on Air Quality and Waste Management for Agriculture
Publication Type: Proceedings
Publication Acceptance Date: 7/15/2010
Publication Date: 9/13/2010
Citation: Miller, D.N., Varel, V.H., Woodbury, B.L., Spiehs, M.J. 2010. Enhanced reduced sulfur emission from manures of beef cattle fed distiller's byproducts. In: International Symposium on Air Quality and Waste Management for Agriculture Proceedings. Septenber 13-16, 2010, Dallas, Texas. 2010 CDROM: 711P0510cd. Interpretive Summary: In two studies examining the level of wet distiller’s grains + solubles (WDGS) fed to feedlot cattle, the reduced sulfur concentrations from both fresh manure and the feedlot surface were increased for animal fed >20% WDGS compared to 0% WDGS. The magnitude of increase varied, but likely enhanced the relative flux of reduced sulfur from fresh manures was 2.5 to 5 times greater when cattle were fed a 40% WDGS diet. Certain areas of the feedlot surface that were wetter and contained more manure exhibited greater fluxes than other areas, and feeding 40% WDGS enhanced the relative flux in these areas by an additional 50%. The impact of feeding 40% WDGS on relative reduced sulfur emissions is unclear, since only a small part of the feedlot pen surface is covered by fresh manure or is considered a high moisture and manure environment. A clearer picture of the extent of these areas would provide a better estimate of how much reduced sulfur fluxes increase when WDGS are fed. Based upon higher relative fluxes observed from wetter, more manure-impacted edge of the pen, a possible strategy to reduce reduced sulfur emissions would be to control manure accumulation (scrape wet sites more frequently) or more intensively manage areas where moisture levels are highest.
Technical Abstract: 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 wet distiller’s grain plus solubles (WDGS), which can be high in sulfur, 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 collected four times from each pen during the study, and the relative emissions were measured using a laboratory wind tunnel chamber. 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 the feedlot surface 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 demonstrate whether this management practice is truly effective.