A115-0002
Field-scale Monitoring of Feedlot Produced Methane and Ammonia using Dual Comb Spectroscopy
Friday, 11 December 2020
Poster
Brian Washburn1, Daniel Herman1,2, Chinthaka Chinthaka Weerasekara3, Lindsay C. Hutcherson4, Fabrizio Giorgetta1,2, Kevin Cossel5, Eleanor Waxman1, Gabriel M Colacion6, Nathan Newbury1, Stephen M Welch7, Brett D DePaola8, Ian Coddington1 and Eduardo Santos9, (1)National Institute of Standards and Technology Boulder Laboratories, Boulder, CO, United States, (2)University of Colorado at Boulder, Boulder, CO, United States, (3)Kansas State University, Agronomy, Manhattan, United States, (4)Kansas State University, Physics, Manhattan, United States, (5)National Institute of Standards and Technology Boulder, Boulder, CO, United States, (6)National Institute of Standards and Technology Boulder Laboratories, Boulder, United States, (7)Kansas State University, agronomy, Manhattan, United States, (8)Kansas State University, physics, Manhattan, United States, (9)Kansas State University, Manhattan, KS, United States
Abstract:
Methane production by livestock enteric fermentation is the largest source of anthropogenic CH
4 emissions in the U.S. Furthermore, ammonia, while not a greenhouse gas, is an important aerosol-generating agricultural pollutant and is challenging to measure in traditional gas sampling systems due to its reactivity and absorptivity. Determining representative livestock CH
4 emissions is challenging due to the high variability of management practices and cattle characteristics in commercial farms. The lack of farm-scale CH
4 emission data leads to large uncertainties in bottom-up greenhouse gas emission inventories and models.
In order to quantify farm-scale CH4 emissions a new class of sensor is required, one capable of long integrated paths, of sensing small concentration enhancements over a large background, and of detecting multiple gases. Open-path dual-comb spectroscopy (DCS) is a novel approach that offers very sensitive, field-scale monitoring of multiple gases by a single laser system. In this work, we demonstrate DCS for the simultaneous quantification of CH4 and NH3 flux from a beef cattle feedlot. A three-month field study with the simultaneous deployment of an open path DCS system and a closed-path cavity ring-down spectroscopy (CRDS) gas analyzer yielded over 10 days of data for comparison of the two techniques. Direct CH4 concentration measurements and calculated fluxes are compared between DCS and traditional CRDS monitoring approaches, showing agreement within 6%. This level of agreement against a standard agricultural measurement technique supports the future use of open-path DCS to quantify flux in cattle grazing or crop based systems. In addition, NH3 emissions were only measured using DCS and its correlation with environmental parameters are explored. Future mid-infrared systems will permit better understanding of N2O emissions due to fertilization, which are particularly interesting since N2O remains an understudied portion of agricultural greenhouse gas emissions.
