Methane Emissions from Natural Gas in the Urban Region of Boston, Massachusetts

Friday, 19 December 2014
Kathryn McKain1, Adrian Down2, Steve M Raciti3,4, John Budney1, Lucy Hutyra3, Cody R Floerchinger5, Scott C. Herndon6, Mark S Zahniser6, Thomas Nehrkorn7, Robert B Jackson2,8, Nathan G Phillips3 and Steven C Wofsy1, (1)Harvard University, Cambridge, MA, United States, (2)Duke University, Durham, NC, United States, (3)Boston University, Boston, MA, United States, (4)Hofstra University, Hempstead, NY, United States, (5)Aerodyne Research Inc., Billerica, MA, United States, (6)Aerodyne Research Inc, Billerica, MA, United States, (7)AER Inc, Lexington, MA, United States, (8)Stanford University, Stanford, CA, United States
Methane emissions from the natural gas supply chain must be quantified to assess environmental impacts of natural gas and to develop emission reduction strategies. We report natural gas emission rates for one year in the urban region of Boston, MA, using an atmospheric measurement and modeling framework. Continuous methane observations from four stations are combined with a high-resolution transport model to quantify the regional average emission rate, 20.6 ± 1.7 (95 % CI) g CH4 m-2 yr-1. Simultaneous observations of atmospheric ethane, compared with the ethane to methane ratio in pipeline gas, demonstrate that natural gas accounted for 58 – 100 % of methane emissions, depending on season. Using government statistics and geospatial data on energy consumption, we estimate the fractional loss rate to the atmosphere from all downstream components of the natural gas system, including transmission, distribution, and end-use, was 2.9 ± 0.3 % in the Boston urban region, compared to 1.1 % inferred by the Massachusetts greenhouse gas inventory.