The 2015 Gininnderra CO2 and CH4 release experiment: An evaluation of gas detection and quantification techniques

A two month long methane and carbon dioxide blind release experiment was held in Canberra, Australia, during 2015. The primary objective of the experiment was to conduct a simultaneous comparison of different atmospheric emissions quantification techniques against a point source release. Seven quantification techniques were assessed during the trial: mobile tracer ratio technique using acetylene and nitrous oxide; open path tracer ratio technique using N2O; backwards Lagrangian stochastic modelling; eddy covariance (3 different approaches); atmospheric tomography using point sensors; atmospheric tomography using integrated line sensors; and Gaussian plume fitting to mobile traverses taken using an unmanned ground robot. The majority of CH4 estimates were within 20% of the actual release rate (5.8 g/min), with the mobile tracer ratio technique providing the closest estimate to both the CH4 and CO2 release rates. The majority of revised CH4 rate estimates, once the release rate was known, were within 10% of the actual release rate. Less accuracy was obtained with the CO2 rate (100 g/min) estimates, underscoring the challenge of accurately quantifying small CO2 emissions. The release also provided an opportunity to assess the effectiveness of mobile CH4 and CO2 detection technologies and other detection technologies. Available sensor detection limits and sampling rates were found to be significant limitations for adequate gas detection for many of the mobile and other detection technologies deployed. Greater success was found with a hyperspectral imager, which was able to clearly image the CH4 release in real time from 100 m distance. Finally, it was demonstrated that a TDLAS laser, equipped with a laser tracking system, was able to successfully track a target on both a moving crane and unmanned aerial vehicle. This encouraging result suggests it may be possible in the future to map gas plumes using a single laser and mobile aerial reflector. Abstract submitted to and presented at the 10th International Carbon Dioxide Conference (ICDC10) 2017 (https://www.ioccp.org/index.php/more/154-10th-international-carbon-dioxide-conference-icdc10-21-25-august-2017-interlaken-switzerland)