(579g) A Quantitative Risk Assessment Framework to Predict and Mitigate Large Unintended Methane Emissions in the Natural Gas Supply Chain

Global natural gas supply continues to expand to meet growing energy demand, primarily driven by population growth. This expansion has been accelerated by the development of horizontal drilling and hydraulic fracturing for unconventional resources, supporting both domestic and international markets. However, increased production has intensified concerns over greenhouse gas emissions across the natural gas supply chain. Methane, the primary component of natural gas and a potent greenhouse gas, is emitted from a wide variety of sources during production, processing, and distribution. Decades of research, supported by continuous monitoring technologies and empirically based quantitative frameworks, have improved the estimation of routine and low-rate unintended methane emissions. However, large unintended emissions, often resulting from equipment malfunctions, abnormal operations, or inadequate maintenance, remain challenging to detect and quantify. A small subset of sources, referred to as super-emitters, has been shown to account for a disproportionately large share of total emissions. These super-emitters may involve specific pieces of equipment or entire facilities and can result from persistent faults or intermittent but intense emission events. Their presence is a key factor in the observed discrepancies between top-down measurements and bottom-up inventories, which often rely on average emission factors and incomplete activity data. To address this gap, we propose a quantitative risk assessment-based framework to predict and mitigate large unintended methane releases. This bottom-up approach adapts established process safety frameworks to estimate the frequency, magnitude, and duration of such events, linking process threats to consequences. Integrating quantitative risk assessment with continuous monitoring enhances detection capabilities, accelerates response, and improves mitigation effectiveness. The proposed framework enables more proactive emissions management and supports improved environmental performance across the natural gas supply chain.