California Air Resources Board

Principal Investigator/Author: Stephen Conley

Contractor: Scientific Aviation, Inc.

Contract number: 18RD032

Project Status: Completed

Relevant CARB programs: California Methane Research Program

Topic areas: Climate Change, GHG Emission Inventory Program, Short-Lived Climate Pollutant Inventory

Research Summary:

Scientific Aviation was contracted by the California Air Resources Board to conduct airborne methane emissions quantifications at a variety of target sites representing known methane source sectors. 199 individual measurements were performed at 114 different target sites between November 18, 2019 – February 26, 2021. Target sites included industrial, agricultural, and waste sources. Several sites from each source type were sampled on more than one occasion to assess temporal variability.

The methodology used by Scientific Aviation is a modified mass balance approach based on Gauss’s Law that has been extensively demonstrated to be accurate and robust and has been published in the peer-reviewed literature. This method involves flying multiple closed-loop patterns around a site of interest at increasing altitudes to fully sample upwind and downwind of a source and the full vertical extent of a plume. An emission rate is determined by using on-board wind measurements and in situ chemical measurements of methane to calculate the mass flow of methane emanating from the target site.

The primary goals of this project were to better understand methane emissions from California’s major emission sectors, including:

• Measurement of important sources in the various primary methane sectors and sub-sectors, with the ability to study whole facility emissions;
• Obtain data for CARB’s Methane Research Program for systematic analysis of facility-level emissions in each sector by measuring different types of sources (geographic locations, size, operational characteristics, etc.) in different seasons; and
• Use a state-of-the-art measurement tool to complement the multi-tiered measurement and analysis research program.

Keywords: airborne methane, methane emissions, methane sources, facility-level, emission sources, methane