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

Andrew Feitz,Peter Reid,Karita Negandhi,Frances Phillips,Nicholas Wokker,David Griffith,Sangeeta Bhatia,Trevor Coates,Ivan Schroder,Stephen White,Stuart Day,Suman George,Stefan Hrabar,Cindy Ong,Joel Wilson,Mark Kochanek,Sean Towner,Steve Zegelin,R A Vincent ,Grant C Edwards ,Ashok K Luhar ,J Malos ,Nicholas M Deutscher ,Martin J Kennedy ,P.m.f Van Der Maas ,Brett C Wood ,Emili Hernández ,M W Hamilton ,Travis A Naylor ,Michael Hatch

doi:10.1016/j.ijggc.2017.11.018

Abstract

A methane (CH4) and carbon dioxide (CO2) release experiment was held from April to June 2015 at the Ginninderra Controlled Release Facility in Canberra, Australia. The experiment provided an opportunity to compare different emission quantification techniques against a simulated CH4 and CO2 point source release, where the actual release rates were unknown to the participants. Eight quantification techniques were assessed: three tracer ratio techniques (two mobile); backwards Lagrangian stochastic modelling; forwards Lagrangian stochastic modelling; Lagrangian stochastic (LS) footprint modelling; atmospheric tomography using point and using integrated line sensors. The majority of CH4 estimates were within 20% of the actual CH4 release rate (5.8 g/min), with the tracer ratio technique providing the closest estimate to both the CH4 and CO2 release rates (100 g/min). Once the release rate was known, the majority of revised estimates were within 10% of the actual release rate. The study illustrates the power of measuring the emission rate using multiple simultaneous methods and obtaining an ensemble median or mean. An ensemble approach to estimating the CH4 emission rate proved successful with the ensemble median estimate within 16% for the actual release rate for the blind release experiment and within 2% once the release rate was known. The release also provided an opportunity to assess the effectiveness of stationary and mobile ground and aerial CH4 detection technologies. Sensor detection limits and sampling rates were found to be significant limitations for CH4 and CO2 detection. A hyperspectral imager’s capacity to image the CH4 release from 100 m, and a Boreal CH4 laser sensor’s ability to track moving targets suggest the future possibility to map gas plumes using a single laser and mobile aerial reflector.

Highlights

Reducing emissions from the extraction, transportation, and burning of fossil fuels is an important mechanism for many countries in order to limit their greenhouse gas emissions by 2030 and thereby reduce the impacts of climate change (UNFCCC, 2015)
A strong diurnal signal is observed for CO2 in Fig. 3, with high CO2 levels present at night primarily as respired CO2 is trapped in the stable atmospheric boundary layer
The closest individual CH4 rate estimate during the blind release experiment was within 2% of the actual release rate and was achieved using the acetylene tracer ratio technique

Summary

Introduction

Reducing emissions from the extraction, transportation, and burning of fossil fuels is an important mechanism for many countries in order to limit their greenhouse gas emissions by 2030 and thereby reduce the impacts of climate change (UNFCCC, 2015). Atmospheric monitoring technologies are an ideal method for investigating fugitive emissions (Jenkins et al, 2012; Zazzeri et al, 2015; Omara et al, 2016) and have been used to estimate emission rates from natural CO2 seepage sites (Werner et al, 2003; Lewicki et al, 2008; Jones et al, 2009). They are likely to play an increasingly important role in the verification of claimed greenhouse emission reductions and quantification of leakage events. High confidence in the accuracy of the quantification methods employed is essential and is a legislative requirement of various governments (Dixon and Romanak, 2015)

Methods

Results

Conclusion