addressing uncertainty in oil and natural gas industry greenhouse

As was shown in Table 5-8, emissions from boilers/heaters, natural gas engines and flares are ranked in the
top ten highest emission sources, with one source, emergency flare, contributing about 62% of the total.
Uncertainty associated with the emergency flare was calculated to be 21.1%, or about ±6,500 tonnes CO 2 e/yr.
By examining the calculations used for flaring, the following general strategies could be selected by the
operating company to reduce uncertainty in flaring:
• Refine the measurement of total gas flared (the activity factor), to reduce the activity factor
uncertainty from the current value of 15% and/or;
• Refine the gas composition measurements to reduce the uncertainty from 4%.
Refining the measurement of total gas flared may result from many approaches, such as improving the meter
quality (even possibly replacing the meter), improving the quality control of the existing meter (such as
number of calibrations and inspections), or improving the number of measurements taken and recorded from
the meter that is used to calculate the total gas flared (this assumes measurements were not already
continuous). These approaches have varying costs, and some may be cost-prohibitive. The company would
have to determine which approach was the most cost effective.
Refining the gas composition data may also come from several methods, such as taking additional routine
samples, installing a continuous gas analyzer, or using a better analysis method. As with the gas flow rate
measurement, these approaches have varying costs, and some may be cost-prohibitive. The company would
have to determine which approach was the most cost effective.
If the company was effective in reducing the uncertainty in flare gas CO 2 emissions, it might then elect to
proceed to the next largest CO 2 uncertainty source. The end-user will have to recalculate total emissions for
the company or facility each time, and determine if the uncertainty goal or target has been reached.
Reduction of Uncertainty in Vented CO 2 Sources
If the company decided to take the next step of emission reductions, it may target the next largest category of
uncertainty, which is vented CO 2 sources. Vented CO 2 emissions result from seven sources listed in
Table F-15. The amine unit accounts for the over 98% of the emissions in this category.
Amine unit CO 2 vented emissions have an uncertainty of 4,360 tonnes of CO 2 e in a category that only has an
uncertainty of 4,420 tonnes of CO 2 e. Therefore any uncertainty reduction efforts in this area should be
directed at the amine unit calculations. However, the calculations used for the amine units reveal that the
uncertainty is actually relatively low. The uncertainty in that emission category is less than 7%. It is possible
to reduce this uncertainty by improving the uncertainties for gas composition, and gas throughput. While it is
possible to reduce this uncertainty, given the low percentage level of the uncertainty, any improvement may
be small. Therefore this is likely a case where company efforts are best spent on the previous categories.
Pilot Version, September 2009 5-23