|Rotz, Clarence - Al|
Submitted to: Journal of Animal Science
Publication Type: Review Article
Publication Acceptance Date: 8/18/2013
Publication Date: 9/17/2013
Citation: Montes, F., Meinen, R., Dell, C.J., Rotz, C.A., Hristov, A.N., Oh, J., Waghorn, G., Gerber, P.J., Henderson, B., Makkar, H., Dijkstra, J. 2013. Mitigation of methane and nitrous oxide emissions from animal operations: A review of manure management options. Journal of Animal Science. 91:5070-5094. Interpretive Summary:
Technical Abstract: This review analyzes published data on manure management practices used to mitigate methane (CH4) and nitrous oxide (N2O) emissions from animal operations. This is the second in a series of reports commissioned by the Food and Agriculture Organization of the United Nations to evaluate mitigation practices for livestock operations. Reducing excreted nitrogen (N) and degradable organic carbon by diet manipulation to improve the balance of nutrient inputs with production is an effective practice to reduce CH4 and N2O emissions. Most CH4 is produced during manure storage; therefore, reducing storage time, lowering manure temperature by storing during colder seasons, and capturing and combusting the CH4 produced during storage are effective practices to reduce CH4 emission. Anaerobic digestion with combustion of the gas produced is effective in reducing CH4 emission and organic carbon content; this increases readily available carbon and N for microbial processes creating little CH4 emission and increased N2O emission following land application. Nitrous oxide emission occurs following land application as a byproduct of nitrification and dentrification processes in the soil, but these processes may also occur in compost, biofilter materials, and permeable storage covers. These microbial processes depend on temperature, moisture content, availability of easily degradable organic carbon, and oxidation status of the environment, which make N2O emissions and mitigation results highly variable. Managing the fate of ammoniacal N is essential to the success of N2O and CH4 mitigation as ammonia is an important component in the cycling of N through manure, soil, crops and animal feeds. Manure application techniques like subsurface injection reduce NH3 and CH4 emissions but can result in increased N2O emissions. Injection works well when combined with anaerobic digestion and solids separation by improving infiltration. Additives such as urease and nitrification inhibitors that reduce microbial processes have mixed results, but are generally effective in controlling N2O emission from intensive grazing systems. Matching nutrient requirements with manure fertilization, managing grazing intensity, and using cover crops are effective practices to increase plant N uptake and reduce N2O emissions. Due to system interactions, mitigation practices that reduce emissions in one stage may increase emissions elsewhere, so mitigation practices must be evaluated at the whole farm level.