Methane source attribution: Methane and Ethane Analysis Using a portable Battery-powered Picarro Cavity Ring-down Spectrometer

Atmospheric methane (CH4) has a powerful short-term global warming impact, and comes from a variety of natural and anthropogenic sources. Methane sources include wetlands, landfills, oil / gas / coal extraction activities, and urban emissions from traffic and the natural gas distribution system. Characterizing the magnitude and the origin of these fugitive emissions spatially and temporally is critical to understand their present and future climate impacts. 

There are two tracer molecules that are often employed to investigate relative importance of various methane sources: d13C in CH4 and ethane (C2H6). Biogenic sources of methane have generally lighter isotope ratios relative to thermogenic sources, although the range for each source is broad and can overlap with the other and therefore hinder the use of d13C values for source discrimination. The main source of atmospheric ethane on the other hand, is fossil energy production and distribution, making it a meaningful tracer for fugitive methane emissions from industrial activities. 

In this study we present a light-weight and fully portable Cavity Ring-Down Spectrometer (CRDS) that precisely measures methane and ethane concentrations. It provides real-time continuous measurements (up to 6 hours) without an upfront separation requirement or multiple analyses to derive the origin of the methane gas. Thanks to its compact and light-weight design it can be carried by the operator as a backpack allowing high precision measurements in industry and research locations far of the electrical grid.