Hamilton, Keith Michael (2017-12). Characterizing Greenhouse Gas Emissions From Feed Yard Operations: Methods and Governing Factors. Master's Thesis.
Thesis
In this research, the uncertainty of commonly used GHG measurement methods was evaluated using Taylor series uncertainty analysis and a field study was performed to evaluate the feasibility of one of these methods. Taylor series uncertainty analysis was performed on three source-integrated methods: monostatic and bistatic open-path Fourier Transform Infrared Spectroscopy (OP-FTIR) and open-path tunable diode laser absorption spectroscopy (OP-TDLAS), and two source-specific methods: non-flow-through non-steady-state (NFT-NSS) and flow-through steady-state (FT-SS) chambers. The average systematic uncertainty for the three source-integrated methods was the same, 15.2%, when determining emission factors for methane (CH4) and nitrous oxide (N2O), except for OP-TDLAS, which did not measure N2O. When determining emission factors from source-specific measurements, NFT-NSS chambers had an average systematic uncertainty of 21.2% and 24.6% for CH4 and N2O, respectively. The FT-SS chambers had an average systematic uncertainty of 13.5% when determining emission factors for CH4 and N2O by a single flux chamber measurement. A field study was conducted in the high plains of Texas at a feed yard with a potential maximum capacity of 50,000 head of cattle. The objective of this study was to determine the feasibility of using an OP-FTIR system to characterize emissions from a ground-level area source with precision. The feed yard was partitioned into multiple sources of CH4 and N2O that included enteric fermentation from the cattle, the manure in the pens, silage storage, manure storage, and a storage lagoon for runoff water from the pens. A bistatic OP-FTIR was placed 27 meters (m) north and parallel to the cattle pens with a path length of 550 m. A meteorological station was also located on this side of the feed yard, 5 meters north of the OP-FTIR path length. The 1-hour average CH4 concentrations were 1.62-6.87 ppm and 1.36-4.97 ppm for downwind and upwind measurements, respectively. Measured 1-hour average N2O concentrations were 168-514 ppb and 203-530 ppb for downwind and upwind measurements, respectively. The downwind and upwind N2O measurements could not be statistically differentiated with the use of a single OP-FTIR system.
