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. 2023 Dec 19;57(50):21092-21103.
doi: 10.1021/acs.est.3c07722. Epub 2023 Dec 4.

The Futility of Relative Methane Reduction Targets in the Absence of Measurement-Based Inventories

Bradley M Conrad  1 , David R Tyner  1 , Matthew R Johnson  1
Affiliations

The Futility of Relative Methane Reduction Targets in the Absence of Measurement-Based Inventories

Bradley M Conrad et al. Environ Sci Technol. .

Abstract

Under the Global Methane Pledge, Canada is developing oil and gas sector methane regulations targeting 75% reductions from 2012 levels by 2030. Without measured baselines and inventories, such policies are ultimately unverifiable and unenforceable. Using the major oil and gas producing province of Saskatchewan as a case study, we derive first-ever measurement-based methane inventories for the region and comprehensively model previous emissions back to the 2012 baseline. Although relative reductions of 23-69% have likely occurred, the dispersion of modeled possibilities and the high emissions from continuing production illustrate the limits of this approach as a meaningful policy metric. Moreover, nearly 90% of apparent reductions are explained by decreased production at heavy oil facilities, suggesting emissions have potential to rebound if production resumes. By contrast, derived measurement-based methane emissions intensities facilitate quantitative assessment and show that despite any past reductions, Saskatchewan's 0.41 ± 0.03 g/MJ intensity remains among the highest in North America. This highlights how relative reduction targets absent measured baselines and inventories are inherently futile and risk rewarding high emitters while obscuring ongoing mitigation potential. Ultimately, required global methane reductions will only be achieved by adopting objectively and independently verifiable emission metrics while measuring and tracking progress toward a net zero future.

Keywords: inventory projections; measurement-based inventory; methane emissions; methane intensity; methane inventory; mitigation targets; oil and gas; regulatory effectiveness.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Map of surveyed facilities and wells in the Province of Saskatchewan in 2020 and 2021 aerial survey. Samples are drawn from each of the four main production regions as defined by the Saskatchewan Government and represent the distribution of facility subtypes as detailed in Tables S1 and S2 of the Supporting Information.
Figure 2
Figure 2
Summary of upstream oil and gas methane inventories for Saskatchewan from Environment and Climate Change Canada’s (ECCC’s) 2012 baseline to recent measurement-based inventories. ECCC’s inventory for all years are shown in green from the 2021, 2022, and 2023 national inventory reports (NIRs). These are compared with inventories derived from satellite data (2019) and the present aerial surveys (2020 and 2021). During 2019–2021, ECCC’s 2023 NIR underestimates measurement-derived inventories by a factor of 1.5–1.6. Crucially, slight methodological changes to the NIR during 2021–2023 show significant variation across reports, highlighting the inherent uncertainty when projecting inventories. *Shen et al.’s satellite-based inventory uses data spanning the 2019 calendar year, from 05/2018–02/2020.
Figure 3
Figure 3
Breakdown of 2021 upstream methane inventories by source type. Pie charts identify (a) the relative contribution of source categories in Environment and Climate Change Canada’s (ECCC’s) 2023 national inventory report and (b) sources in the present measurement-based inventory. SCVF = Surface Casing Vent Flow; CHOP(S) = Cold Heavy Oil Production with or without Sand. Refer to Figure S3 for the equivalent results from 2020.
Figure 4
Figure 4
Projections of the 2021 measurement-based inventory to estimate relative reductions in methane emissions from the ECCC baseline year of 2012. Relative reduction of methane emissions since 2012 are plotted for all projection scenarios (a) alongside simultaneous relative changes in production (b), including a notable 70% drop in production at single-well CHOP(S) (SW-CHOP(S)) sites. Absolute provincial methane intensities are also plotted for all projections, with an average reduction of 53% since 2012 (c). Subplot (d) plots the projection-averaged absolute change in methane emissions since 2012 alongside the change at SW-CHOP(S) alone. These data, coupled with the negligible change in methane intensity at SW-CHOP(S) sites (d), suggest that nearly all methane reductions in Saskatchewan can be attributed to reduced SW-CHOP(S) production.
Figure 5
Figure 5
Methane intensities of conventional (non oil sands) oil and gas production across North American basins.,,,, (a) Methane intensities for Western Canadian provinces independently and in aggregate via the present study, other 2021 aerial surveys,, and satellite observations during May 2018 to February 202011. Additional downstream contributions from the ECCC NIR are added in white to give total sector values. (b) Methane intensities for American basins from satellite observations during 2018 and 2020 and a bottom-up analysis for 2015 (which separately estimates a downstream contribution as similarly shown in white). *Excludes the province of Manitoba.
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