California Air Resources Board

Background 

The California Energy Commission (CEC) in collaboration with the California Air Resources Board envisioned and supported a coordinated research effort to survey methane emissions from the natural gas system from wells to final consumption. In response to the Aliso Canyon natural gas leak incident, the California Energy Commission asked Scientific Aviation, a member of the research team, to conduct a number of airborne flight measurements to quantify the methane leak rates at Aliso Canyon and subsequently at all the natural gas storage facilities in California. These flights provided a relative comparison of the leak rates at each of the natural gas storage facilities, and are also serving as a baseline for upcoming research efforts. The table below also includes background information  about  the natural gas storage facilities, such as age of the infrastructure and storage capacity. 

Researchers use a small airplane equipped to measure methane and ethane concentrations in real-time. Ethane uniquely identifies methane from a fossil fuel source, such as a natural gas reservoir, and allows the methane plume to be distinguished from other sources. By flying through the downwind methane plume at various elevations, a methane leak rate can be calculated. 

The figure below compares the average emissions rate at Aliso Canyon during the leak with the average emissions rate at all the natural gas storage facilities in the State where measurements have been made. Emissions at natural gas storage facilities constitute less than 1% of statewide methane emissions. Individual results can be found in the provided chart. CARB and CEC intend to continue to monitor methane emissions from the natural gas infrastructure, including the underground storage facilities, and will continue to update this website as new data becomes available.