Designing Surface Monitoring Meshes for Geologic Carbon Capture and Storage Sites: Accurate Emissions Accounting for an Essential 2°C Mitigation Technology

Abstract:

Geologic carbon capture and storage (CCS) is a feasible solution to the international greenhouse gas (GHG) emissions problem and it has recently been called a "vital" mitigation tool by the International Energy Agency. However, there exists uncertainty concerning the terminal fate of stored carbon dioxide (CO₂.) In this regard, reliable monitoring, verification and accounting (MVA) technologies are essential for making CCS publicly acceptable. Chiefly, MVA addresses safety and environmental concerns by providing a warning system to prevent or alleviate CO₂ leakages. A secondary purpose of MVA technologies is to prove compliance with CO₂ reduction standards through inventory verification. A key MVA tool for tracking CO₂ leakages is surface (atmospheric) monitoring. Demonstrating its value, industry actors feel an impetus to invest in surface monitoring as a low-risk, high-value technology to mitigate liability in cases of potential leakages. Despite how necessary this tool is, to date, all surface monitoring mesh designs and best practices have been proposed locally, without discussion of standardization or optimization on a regional, national or international level. We identify the fundamental problem of surface monitoring mesh design as locating the monitoring sites to record CO₂ levels over the designated geographic area at lowest cost with maximum impact. We approach this problem from both an operations research (OR) perspective and atmospheric dispersion perspective. From an OR perspective, we approach mesh design using multiobjective optimization models – we specify the relative placement of candidate sites, observation time interval, and optimality criteria. In the second approach, we model CO₂ leakage scenarios to test the effectiveness of proposed mesh design from the first approach. We use atmospheric dispersion modeling softwares AERMOD and SCREEN3 – both tools developed by the United States Environmental Protection Agency and codified into law – for modeling point-source gaseous leakages at the earth's surface. In conclusion we show standardized, optimized mesh designs for known atmospheric conditions, we present a robust decision support tool for decision-makers, and we discuss implementation from both an economic and legal perspective.