An innovative way to quantify greenhouse gas emissions in Canada’s oil sands
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 the Specified Gas Emitter Regulation (SGER), 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.
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. 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.
IDM combines multiple ambient CO2 and 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;
- accurate estimates of mobile emissions in and around the mine, and their impact on our measurements;
- 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; and
- regulatory oversight throughout the project by Alberta Environment and Parks (AEP).
Despite significant technical challenges, this new approach was deemed successful and the results supported regulatory reporting under SGER in 2015 and 2016. Based on the continued success, a similar approach was used again in 2017.
Under this new approach it remains difficult to ensure good representative measurements above background levels. Modeling in-pit meteorology and mobile emissions also presents a significant challenge. Nevertheless, by relying on net concentrations of emissions from all parts of the tailings pond and mine, for several days, the 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 emission estimates.
Scientific papers describing the project have been accepted for presentation at major oil-gas (Canada’s Oil Sands Innovation Alliance (COSIA)) and scientific (Air and Waste Management Association (AWMA)) conferences.