Dairy manure is an important emission source of methane, a short-lived climate pollutant, in California. The volatile solids (VS) and nitrogen (N) species contained in manure can be converted to methane (CH4) and/or nitrous oxide (N2O), and the emission factors (EFs) vary strongly with manure management systems. Hence, it is important to characterize VS and N concentrations in manure under various manure management systems. Currently, California uses the U.S. EPA's assumptions regarding the chemical contents and subsequent EFs in methane emissions from manure management but California-specific dairy data is needed for an improved emission inventory. This project evaluated dairy demographics in San Joaquin Valley (SJV), identified major types of animal housing facilities and manure management systems, and measured VS concentrations and other chemical parameters in manure, along with the animal residence time on concrete (TOC), in four representative dairy farms with two predominant housing systems: freestall and nonfreestall (drylot). TOC is a key parameter dictating the manure management downstream from animal housing to manure storage ponds. Results of this study indicated great variability in TOC (21 percent to 78 percent) with different dairy farms or cattle groups, and in VS concentrations (0.12 percent to 12 percent) with manure 22 management practices such as the use of solid-liquid separation technologies. The California-specific information provided by this study on manure management and properties can be used to inform manure emission calculations or future research planning on manure emissions, as well as the development and evaluation of Alternative Manure Management Practices in California dairies.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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