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

Abstract

Nitrous oxide (N 2 O) is a greenhouse gas with about 300 times the global warming potential (GWP) of carbon dioxide (CO 2 ). 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 N 2 O 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 N 2 O 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, N 2 O infrared absorption bands were identified in the FTIR spectra of the silage gas by comparing them to both standard N 2 O gas and simulated infrared spectra which confirmed that N 2 O was present in the silage gas. Then, N 2 O 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 N 2 O concentrations in the silage gas.