Observations of Methane Emissions from Natural Gas-Fired Power Plants

Observations of Methane Emissions from Natural Gas-Fired Power Plants

Natural gas

Methane

Carbon dioxide

Uncertainty analysis

Gas emissions

Natural gasoline plants

Fossil fuel power plants

Environmental Protection Agency

Current research efforts on the atmospheric impacts of natural gas (NG) have focused heavily on the production, storage/transmission, and processing sectors, with less attention paid to the distribution and end use sectors. This work discusses 23 flights at 14 natural gas-fired power plants (NGPPs) using an aircraft-based mass balance technique and methane/carbon dioxide enhancement ratios (I"CH4/I"CO2) measured from stack plumes to quantify the unburned fuel. By comparing the I"CH4/I"CO2 ratio measured in stack plumes to that measured downwind, we determined that, within uncertainty of the measurement, all observed CH4 emissions were stack-based, that is, uncombusted NG from the stack rather than fugitive sources. Measured CH4 emission rates (ER) ranged from 8 (5) to 135 (27) kg CH4/h (1), with the fractional CH4 throughput lost (loss rate) ranging from-0.039% (0.076%) to 0.204% (0.054%). We attribute negative values to partial combustion of ambient CH4 in the power plant. The average calculated emission factor (EF) of 5.4 (+10/-5.4) g CH4/million British thermal units (MMBTU) is within uncertainty of the Environmental Protection Agency (EPA) EFs. However, one facility measured during startup exhibited substantially larger stack emissions with an EF of 440 (+660/-440) g CH4/MMBTU and a loss rate of 2.5% (+3.8/-2.5%). 2019 American Chemical Society.

8976-8984

15

53

Environmental Science and Technology

2019

Hajny, Kristian D.

Salmon, Olivia E.

Rudek, Joseph

Lyon, David R.

Stuff, Andrew A.

Stirm, Brian H.

Kaeser, Robert

Floerchinger, Cody R.

Conley, Stephen

Smith, MacKenzie L.

Shepson, Paul B.

journalArticle

0013936X

10.1021/acs.est.9b01875