Dr. Xu Li
Date of this Version
The emission of methane from livestock production contributes to climate change. Cattle manure accounts for one-third of the total methane emission over the lifecycle of beef and dairy production and represents an opportunity to lower the environmental footprint of the beef industry. While models have been developed to estimate methane emissions from manure under certain types of manure storage methods, there is a lack of a user-friendly interface that agricultural or environmental engineers can use to estimate the methane emission from manure for specific regions. Therefore, the goal of this study was to build an interface to estimate methane emissions factors (EFs) and overall methane emissions for the beef cattle manure in Nebraska under various manure management scenarios.
The Tier 2 model developed by the Intergovernmental Panel on Climate Change was adopted in the study. Besides, a typical scenario of beef cattle production in Nebraska was adopted in the study, where animals grow an average weight of 318 kg hd-1 to 635 kg hd-1 during the 200 days in feedlots. The interface developed in this study encompasses four major manure management systems: solid storage, uncovered anaerobic lagoon, composting static pile, and daily spread. A range of temperatures, from 10 to 28ºC, were considered in the study.
For solid storage, the EFs were calculated to range from 0.98 to 3.05 kg CH4 hd-1 yr-1 and the overall emissions from 5.89 to 18.29 Gg CH4 yr-1 for the 2.82 million heads of beef cattle in Nebraska in the Year 2021. Higher EFs were found for liquid storage, averaging at 37.69 and 45.68 kg CH4 hd-1 yr-1 in winter and summer, respectively. Furthermore, overall emissions can reach 226 Gg CH4 yr-1 on a winter day and 274 Gg CH4 yr-1 in the summer. After analyzing the methane emissions from both solid and liquid storage, it is noticeable that moisture content plays an important role in methane production. The methane production trend falls when the moisture content decreases, confirming that a reduction of the water content of manure could potentially lower CH4 emissions from manure. Thus, this observation opens the possibility to investigate the feasibility of reducing water in manure as a mitigation measure for methane emission.
Advisor: Xu Li