An innovative approach to greenhouse gases in Canada's oil sands and coal mines
Alberta oil sands contribute about 9% of Canada’s greenhouse gas (GHG) emissions. Canada, Alberta, and the oil and gas industry are committed to reducing overall GHG emissions. Under Carbon Competitiveness Incentive Regulation (CCIR), oil sands mining operations are required to quantify and report annual fugitive GHG emissions. A major oil sands producer retained RWDI to conduct measurements of area fugitive emissions at their tailings pond and mine each summer since 2015, and quantify related fugitive GHG emissions using a novel approach.
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The Challenge
The traditional measurement and quantification methodology relies on the use of punctual flux chamber measurements, which are then scaled into annual GHG estimates for entire ponds and mining areas. Regulators and industry experts acknowledge the limitations of this approach: because the emissions are spatially inhomogeneous and temporally variable, spot measurements can produce large, unrealistic year-to-year differences. Methane emissions from vertical face mines, unreachable parts of the ponds, and mine floor cracks are also missed. The use and validation of alternative methods have thus been encouraged. We proposed Inversion Dispersion Modeling (IDM) as a more effective approach to this measurement and quantification challenge; our client embraced the idea.
Our Approach
IDM combines multiple ambient CH4 measurements around the tailings ponds and mines, with meteorological and dispersion modeling, and an inversion technique to retrieve GHG emission rates. The use of IDM to quantify fugitive emission sources has strong scientific and regulatory precedents. However, it was a first for oil sands tailings ponds and mine areas. As a result, our use of IDM in this context necessitated:
- proof of concept (in particular making sure CO2 and CH4 levels could be detected and quantified above ambient background levels);
- two-week field campaigns each summer, with multiple open-path lasers, portable sensors, FTIR / Eddy Covariance instruments, and sonic anemometers;
- advanced meteorological and dispersion modeling (CALPUFF) suited to the complex terrain in the mine pit;
- a statistical inversion technique;
- independent validation (conducted by University of Alberta researchers, who assisted in the data collection and performed their own IDM analysis);
- the use of the traditional approach alongside this new approach, for continuity and comparison purposes;
- regulatory oversight throughout the project by Alberta Environment and Protected Areas (AEPA); and
- participation in a multi-technology field campaign during the Emission Reduction Alberta Challenge to validate and compare methane quantification technologies.
The Outcome
Overcoming significant technical challenges, this new approach was deemed successful and results have been supporting regulatory reporting under CCIR ever since 2015.
A review by an independent panel of a range of technologies co-deployed during the ERA Challenge identified CALPUFF-IDM as the most appropriate for quantifying GHG emissions from large area sources, including in the complex terrain of a mine.
CALPUFF-IDM was then formally approved by AEPA as an alternative methodology to quantify annual fugitive methane emissions from oil sands tailing ponds and mines, and other large area sources such as coal mines and landfill in 2023.
Modeling in-pit meteorology presents a significant challenge and a high resolution meteorological model is a must.. Nevertheless, by relying on net concentrations of emissions from all parts of the tailings pond and mine, for several days, the CALPUFF-IDM method achieved a spatially and temporally representative survey of the sources. In this way it avoided key shortcomings of the traditional flux chamber approach.
Because of its non-intrusive nature (measurements are made outside the active areas) the IDM method allows for continuous long-term monitoring and offers additional advantages in terms of practicality and safety. It is non-instrument specific and can be used in conjunction with a variety of measurement technologies (provided they are sensitive and accurate enough). Continuous monitoring throughout the year would provide seasonal, and ultimately even more representative, annual methane emission estimates. Furthermore, the approach gives 2D maps of methane emission intensities allowing for targeted mitigation. The CALPUFF-IDM method has since been used in a number of open-pit mines around the world.
Scientific papers describing the project have been presented at major oil-gas (Canada’s Oil Sands Innovation Alliance (COSIA)) and scientific (Air and Waste Management Association (AWMA) and Clean Air Society of Australia and New Zealand (CASANZ)) conferences.