Global warming has been linked to Greenhouse Gas (GHG) emissions. Swine operations are important sources of GHG, primarily methane (CH4) and nitrous oxide (N2O). The Intergovernmental Panel on Climate Change (IPCC) has developed guidelines for estimating and reporting emissions of GHG. However, the methodology proposed by the IPCC is relatively crude. There is a need to improve the estimates of emissions. A statistical analysis (meta-analysis) on measured GHG emissions in existing studies as well as a literature review was performed to reveal possible bias in estimation of GHG emissions from swine operations and to explore causes of the variation in the reported GHG emissions from swine buildings, manure storage facilities and manure land applications. In total, 96 studies were included in the meta-analysis. The results showed that variation of the measured CH4 and N2O emission rates has not been adequately captured by the IPCC approaches. Larger differences between estimated and measured CH4 emission rates were observed in North American studies than in European studies. In North American studies, the IPCC approaches have a tendency to overestimate CH4 emissions, especially from lagoons at lower temperatures. For N2O emissions from swine operations, an overall underestimation of the IPCC approaches was observed in European studies but not in North American studies. The measured GHG emissions from swine operations were significantly affected by types of emission sources, swine categories (stage of production) and geographic regions. Farrowing swine emitted more CH4 and CO2 emissions as compared with other swine categories, while gestating swine had greater N2O emissions. Effects of different manure handling systems, bedding material, manure removal frequency, use of covers on manure storage facilities, temperature and diet crude protein (CP) content were investigated through meta-analysis. For N2O emissions from swine manure applications, the IPCC default emission factor is within the range of measured values. Factors that can affect the GHG emissions from manure land applications include: temperature, precipitation, soil properties, manure application methods, manure application time, and composition/treatment of manure, etc. The results provided a better understanding on causes of variation in GHG emissions from swine operations. It can help to quantify the emissions more accurately. The knowledge on causes of variation may also be useful for developing cost-effective mitigation strategies.
Contact information: Zifei Liu, 919-292-4085"", [email protected]