es5b04712_si_001.pdf (281.52 kB)
Black Carbon Emissions from Associated Natural Gas Flaring
journal contribution
posted on 2016-02-09, 17:20 authored by Cheryl L. Weyant, Paul B. Shepson, R. Subramanian, Maria
O. L. Cambaliza, Alexie Heimburger, David McCabe, Ellen Baum, Brian H. Stirm, Tami C. BondApproximately
150 billion cubic meters (BCM) of natural gas is
flared and vented in the world annually, emitting greenhouse gases
and other pollutants with no energy benefit. About 7 BCM per year
is flared in the United States, and half is from North Dakota alone.
There are few emission measurements from associated gas flares and
limited black carbon (BC) emission factors have been previously reported
from the field. Emission plumes from 26 individual flares in the Bakken
formation in North Dakota were sampled. Methane, carbon dioxide, and
BC were measured simultaneously, allowing the calculation of BC mass
emission factors using the carbon balance method. Particle optical
absorption was measured using a three-wavelength particle soot absorption
photometer (PSAP) and BC particle number and mass concentrations were
measured with a single particle soot photometer. The BC emission factors
varied over 2 orders of magnitude, with an average and uncertainty
range of 0.14 ± 0.12 g/kg hydrocarbons in associated gas and
a median of 0.07 g/kg which represents a lower bound on these measurements.
An estimation of the BC emission factor derived from PSAP absorption
provides an upper bound at 3.1 g/kg. These results are lower than
previous estimations and laboratory measurements. The BC mass absorption
cross section was 16 ± 12 m2/g BC at 530 nm. The average
absorption Ångström exponent was 1.2 ± 0.8, suggesting
that most of the light absorbing aerosol measured was black carbon
and the contribution of light absorbing organic carbon was small.