Dairy manure systems produce greenhouse gas and ammonia emissions that contribute to climate change. There are many potential practices and management strategies that can reduce these emissions which can conserve nutrients and reduce environmental impacts. This work assesses different processing strategies, additives, and manure storage covers to reduce emissions from dairy manure systems.
We completed three laboratory/field trials to assess emissions from manure systems. The first trial was to assess the greenhouse gas and ammonia emissions during storage and land application of manure that was processed with solid separation and digestion in combination with solid separation. A second trial assessed emissions and manure characteristics from storage with various commercial additives. The third study assessed ammonia emissions from digested manure storages with various biomass covers including raw wood, steam treated wood, and biochar produced from wood and corn cobs.
The results from the study indicate that separation and digestion result in significant reductions in greenhouse gas emissions. However, as expected, ammonia emissions following digestion are increased due to increased nitrogen mineralization. Results also indicate that separation alone had a similar impact to greenhouse gas emissions, but did not further reduce emissions following digestion. Commercially available products that are designed to be added to manure storages had little to no impact on emissions or manure characteristics for the conditions present in this study. Lastly, biochar was capable of reducing ammonia emissions significantly when applied as a cover. Although the biochar was capable of sorbing ammonical nitrogen, the results indicate that the physical barrier on the manure surface was the primary driver for the reduction in ammonia emissions.
Following the outcomes of this work, information is being added to a dairy manure life cycle assessment to determine larger system wide impacts from changes in management practices or the inclusion of a processing system. In addition, work is being conducted to look at potential benefits that may be gained over a number of impact factors when manure management systems are optimized with other waste management systems from the municipal sector.
Rebecca Larson, Assistant Professor, University of Wisconsin-Madison
M.A. Holly, Agricutural Engineer at USDA ARS, J.M. Powell, Soil Scientist at USDA ARS, H. Aguirre-Villegas, Assistant Scientist at University of Wisconsin-Madison
Holly, M.A., R.A. Larson, M. Powell, M. Ruark, and H. Aguirre-Villegas. 2017. Evaluating greenhouse gas and ammonia emissions from digested and separated manure through storage and land application. Agriculture, Ecosystems & Environment, 239:410-419. http://www.sciencedirect.com/science/article/pii/S0959652616321953
Holly, M.A. and R.A. Larson. 2017. Effects of Manure Storage Additives on Manure Composition and Greenhouse Gas and Ammonia Emissions. Transactions of the ASABE, Accepted in Print.
Holly, M.A. and R.A. Larson. 2017. Evaluation of Biochar, Activated Biochar, and Steam Treated Wood as Dairy Manure Storage Covers for Ammonia Mitigation. In Review.