Supplementary Methods
Estimating leaks from the Russian natural gas transport system
In 1996 and 1997, a first series of CH4 emission flux measurements was performed in
Yamburg, western Siberia, at three gas production and processing facilities, two compressor
stations and along sections of transmission pipelines1.
In May, June and October 2003 we have extended these measurements, investigating
leaks, discharge emissions and accidental releases of the Gasprom gas network (Table S1).
We cooperated with the largest natural gas production and transportation company, Gazprom,
and the associated Vniigaz research institute in Moscow, providing logistical support and
technical data, including records of maintenance and accidents. We focussed on the two main
east-to-west high pressure gas transport lines (more than 3000 km each), comprising three to
five pipes in parallel, with diameters up to 1.4 m, operated at 55-75 bar. One runs from
Urengoy westward (built before 1970) and the other from Yamburg (built between 1980 and
1990). The selection of these five measurement areas was based upon geographical and
infrastructural criteria, aimed at a representative sampling of types and ages of machinery and
pipeline sections (Table S2). In each area several teams of scientists and technicians
performed measurements and collected supplementary data during one week. We employed
both German and Russian CH4 detectors as well as equipment for volumetric measurements,
cross-calibrated and certified before each campaign. The instrumental uncertainty of the CH4
flux measurements has been estimated at ±15%.
The measurements have been carried out in two steps. First a “screening” was
performed to determine the locations of gas leaks. Second, the leaking equipment has been
wrapped into plastic foil for volumetric measurements. An impression of the equipment
involved is given in Figure S1. Venting openings and pipes from machines, switches and
connectors were sampled directly. Gas releases from repairs, maintenance and accidents have
been estimated from reports by regional gas companies to Gazprom. The total amount of gas
lost by accidents has been estimated from the volume and the pressure of the pipeline sections
involved. We have corrected for the partial combustion of CH4, because in about 60% of all
accidents the escaping gas ignites (thus releasing CO2 in stead of CH4). According to
Gazprom/Vniigaz the number of accidents has reduced as a result of regular inspection flights
and the use of guided pipeline probes.
At each location several hundred kilometre pipeline sections (300-1200 km single pipe
equivalent) were inspected by infrared remote sensing (applying the gas correlation principle)
from a low flying helicopter (~50 m altitude). Elevated CH4 concentrations have been
observed over large areas with flooded soils, attributed to bacterial production rather than
pipeline leakages, because the latter produce localized enhancements. This is corroborated by
measurements along the Trans-Siberian railroad2, showing relatively high CH4 concentrations
in summer and near-background concentrations in winter when bacterial activity in wetlands
is low.
The CH4 emission factors have been calculated by accounting for the number and size
of leaks per component (Table S3). The activity data, needed to compute the emission fluxes,
and other emissions such as CO2-emissions from turbine exhausts and electricity production
have been derived from the machine operation times, and statistics of maintenance, repairs
and accidents. The averages and uncertainty ranges have been obtained with a Monte Carlo
method, as recommended by the Intergovernmental Panel on Climate Change and the US
Environmental Protection Agency to determine the confidence ranges of greenhouse gas
inventories4. As a result we estimate that leaks and accidental gas releases from pipelines
amount to 6,531 m3 km-1 year-1 and from compressor stations 55,683 m3 MW-1 year-1. By
extrapolating to the Russian natural gas transportation system (Table S4), the overall
emissions are estimated at 0.7% (95% confidence interval is 0.4-1.6%).
References
1.
2.
3.
Dedikov, J. V. et al.. Estimating methane releases from natural gas production and transmission in Russia.
Atmos. Environ. 33, 3291-3299 (1999).
Oberlander, E. A., Brenninkmeijer, C. A. M., Crutzen, P. J., Lelieveld, J. & Elanski, N. F. Why not take the
train? Trans-Siberian atmospheric chemistry observations across Central and East Asia. EOS Transactions
83, 509-516 (2002).
Lechtenböhmer, S., et al. GHG-emissions of the natural gas life cycle compared to other fossil fuels (in
Europe). Proceedings of the 3rd international methane and nitrous oxide mitigation conference, pp 790-798,
17-21 November, Beijing, China ‹http://www.wupperinst.org› (2003).