@article{30705,
  author = {Marc L Fischer and Wanyu R Chan and William W Delp and Seongeun Jeong and Vi H Rapp and Zhimin Zhu},
  title = {An Estimate of Natural Gas Methane Emissions from California Homes},
  abstract = {<p>We estimate post-meter methane (CH<sub>4</sub>) emissions from California’s residential natural gas (NG) system using measurements and analysis from a sample of homes and appliances. Quiescent whole-house emissions (i.e. pipe leaks and pilot lights) were measured using a mass balance method in 75 California homes, while CH<sub>4</sub> to CO<sub>2</sub> emission ratios were measured for steady operation of individual combustion appliances and, separately, for transient operation of three tankless water heaters. Measured quiescent whole-house emissions are typically &lt; 1 g CH<sub>4</sub>/day, though exhibit long tailed gamma distributions containing values &gt; 10 g CH<sub>4</sub>/day. Most operating appliances yield undetectable CH<sub>4</sub> to CO<sub>2</sub> enhancements in steady operation (&lt; 0.01% of gas consumed), though storage water heaters and stove-tops exhibit long tailed gamma distributions containing high values (~ 1-3% of gas consumed), and transients are observed for the tankless heaters. Extrapolating results to the state-level using Bayesian Markov chain Monte Carlo sampling combined with California housing statistics and gas use information suggests quiescent house leakage of 23.4 (13.7 – 45.6, at 95% confidence) Gg CH<sub>4</sub>, with pilot lights contributing ~ 30%. Emissions from steady operation of appliances and their pilots is 13.3 (6.6 – 37.1) Gg CH<sub>4</sub>/yr, an order of magnitude larger than current inventory estimate, with transients likely increasing appliance emissions further. Together, emissions from residential NG are 35.7 (21.7 – 64.0) Gg CH<sub>4</sub>/yr, equivalent to ~ 15% of California’s NG CH<sub>4</sub> emissions, suggesting leak repair, improvement of combustion appliances, and adoption of non-fossil energy heating sources can help California meet its 2050 climate goals.</p>},
  year = {2018},
  journal = {Environmental Science & Technology},
  month = {02/2018},
  issn = {0013-936X},
  doi = {10.1021/acs.est.8b03217},
  language = {eng},
}