Assessment of methane emissions from the U.S. oil and gas supply chain

This paper brings together recent studies to assess emissions from the oil and gas supply chain (i.e. all operations associated with the production, processing, and transport of oil and gas). Specifically, the paper integrates results of recent facility-scale bottom-up studies (i.e. studies that aggregate and extrapolate measured emissions from equipment, operations, or facilities, thereby generating regional/state/national emission estimates) in order to estimate methane emissions from the US oil and gas supply chain. It then validates those results using top-down studies (i.e. studies that quantify ambient methane enhancements and aggregate emissions from sources that contribute to emissions across geographies), using nine basins for this study. 

The study finds that the estimates of methane emissions from US oil and gas supply are higher than estimated in the US Environmental Protection Agency’s Greenhouse Gas Inventory. Specifically, the paper’s bottom-up estimate is 63% higher. The paper suggests this is because the sampling methods used in conventional greenhouse gas inventories underestimate emissions by failing to capture and include emissions from abnormal operating conditions. Accordingly, the paper notes the pressing need to include equipment-based measurements to capture such emission events. Furthermore, considerable emissions reductions could be achieved if systems are put in place that are well-designed to detect and repair abnormally operating equipment. 

Ultimately, the paper suggests that large emission reductions are feasible. It also suggests that many mitigation options are possible to detect the root causes of high emissions from abnormal conditions and to put in place less failure-prone systems. 

This article can be used to scrutinise claims of emissions efficiency measurements in conventional greenhouse gas inventories, to demonstrate that they may not capture the full extent of emissions. It can also be used to demonstrate the importance of regulating upstream processes to minimise emissions. Where a project will not be rejected, the article can be used to advocate for the imposition of stringent conditions on the permit to ensure the lowest emissions can be achieved through the use of well-designed detection and repair systems.