Using IR-based sensors to monitor fugitive greenhouse gas emissions in the Australian context

Abstract

For the same amount of power generated, natural gas has approximately 50 to 60 percent less emissions relative to coal. However, methane (the main constituent of natural gas) has a greenhouse warming potential approximately 30 times higher than CO2. In the transition to lower emissions for energy generation, the contribution to overall greenhouse gas emissions is expected to increase for natural gas as its demand increases when coal is replaced. However, given the potency of methane as a greenhouses gas, fugitive emissions monitoring and an accurate assessment is very important. Agriculture, bushfires, wetlands and termites are also significant contributors to methane emissions and have significant seasonal and spatial variations. In recent surveys either conducted or supported in Australia by CSIRO, a variety of approaches (e.g. vehicle-based survey, fixed-site monitoring stations) and technologies (e.g. near-IR cavity ring down spectroscopy) for fugitive emissions monitoring have been tested and implemented. In general, to be suitable for field work in the Australian context, sensors need to be very stable and robust under very harsh conditions as well as being able to selectively detect ppb or even sub-ppb variations in gas concentrations. More recently, alternatives to the older cavity ring down spectroscopy approach have been developed which use mid-IR region of the spectra. These have improved sensor cost, robustness and performance as well as lowering size and power requirements. These new commercially available technologies based on mid-IR lasers provide an opportunity to deploy these sensors at fixed stations on a much wider scale. This paper will examine the different approaches used in different survey scenarios comparing their effectiveness within the Australian context. This includes new approaches that have recently become possible with these new advances in technology. Based on the survey work that has been conducted, some of the common findings that have been found through surveys in Western Australia, Victoria, Queensland and the Northern Territory will be presented to demonstrate the capabilities of these sensors.