This paper uses the best-available science to estimate of the rate of leakage of natural gas from extraction to end-user (“lifecycle”) for natural gas used within California. Methane, the primary component of natural gas, is a very powerful short-lived climate pollutant. Understanding the rate at which methane escapes from the natural gas system has important implications on both short term climate impacts and long-term infrastructure planning for a low-carbon future. The California Greenhouse Gas Inventory compiled by the Air Resources Board accounts for emissions from sources and activities that occur only within state boundaries. As California imports 90% of the natural gas consumed within the State, excluding emissions from out-of-state processes can skew how the carbon intensity of different energy sources compare to each other and how greenhouse gas mitigation programs are chosen. This paper found that natural gas consumed in California has a lifecycle leak rate of 3.6% [2.4 – 4.3]%.
….for comparison purposes, studies have revealed that if 2% of natural gas leaks before being combusted for end use, the climate benefit from the use of natural gas instead of coal is negated (Wigley 2011).