Detecting Nitrous Oxide in Complex Mixtures Using FTIR Spectroscopy: Silage Gas

Abstract

Nitrous oxide (N2O) is a greenhouse gas with about 300 times the global warming potential (GWP) of carbon dioxide (CO2). It is emitted from a wide range of sources and is responsible for about 6% of anthropogenic US greenhouse gas emissions. Analytical techniques are needed that can measure concentrations of N2O rapidly and inexpensively in sources that are also emitting other compounds that may interfere with the analytical process. In this work, we demonstrate the use of Fourier Transform Infrared (FTIR) spectroscopy to analyze N2O in the complex mixture of gases produced during the early phase of the silage making process. Silage gas samples were collected into Tedlar bags from the bucket silos during the first week of corn ensiling. A bag of the silage gas was analyzed using a Bruker FTIR spectrometer coupled with a long optical path length White Cell. First, N2O infrared absorption bands were identified in the FTIR spectra of the silage gas by comparing them to both standard N2O gas and simulated infrared spectra which confirmed that N2O was present in the silage gas. Then, N2O concentration in the silage gas was derived from the FTIR spectra using LINEFIT program. It was demonstrated that FTIR spectroscopy is a viable method for measuring N2O concentrations in the silage gas.