| dc.description.abstract | 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. | en |
