1. Uncertainty of carbon dioxide emission factor for natural gas
Marija Zivkovic, Dejan Ivezic,
Dusan Danilovic, Aleksandar Madzarevic
University of Belgrade-Faculty of Mining and Geology, Serbia
Athens, October 2012.

2. Motivation
Structure of primary energy consumption of The Republic of Serbia:
coal 53%,
oil 28%,
natural gas 13%,
RES 6%.
Share of domestic production of natural gas is between 10% and 15%

3. Motivation
Composition of natural gas in some deposits in Serbia, volumetric %

4. Motivation
Lower heating value of natural gas produced in Serbia, (Kacanski, 2012)
Ballast content of natural gas produced in Serbia-volumetric, (Kacanski, 2012)

5. Uncertainty of carbon dioxide emission factor for natural gas
Emission factor proposed for natural gas: 56,1 kg/GJ, or 15,3 tC/TJ (IPCC, 1996).
Besides carbon dioxide product of oxidation, carbon dioxide -ballast component of natural gas is emitted too.
Need for reconsideration of emission factor for natural gas with high ballast content.

6. Carbon dioxide emission factor for natural gas -result of combustion

7. Carbon dioxide emission factor for natural gas -result of combustion
Carbon dioxide emission factor which is result of the combustion of combustible components is almost constant and its value is approximately 55 kg/GJ.
Growth of ballast content in the fuel induce reduction of the of combustible carbon content, reduction of the mass of carbon dioxide emitted, but also induce reduction of the net calorific value of the fuel.
Combination of these two influential parameters makes an approximately constant ratio

8. Overall carbon dioxide emission factor

9. Overall carbon dioxide emission factor
Gas samples 1, 9 and 14 represent examples of gas with high content of hydrocarbons and negligible ballast, which makes the difference between emission coefficients negligible.
Gas sample 8 is an example of gas with low content of hydrocarbons, and significant presence of ballast (higher percentage of carbon dioxide than nitrogen).
Gas sample 7 is similar with sample 8 concerning hydrocarbons content in gas but compared to sample 8, nitrogen is predominant in ballast

10. Overall carbon dioxide emission factor
Correlation of carbon ballast fraction and addition to emission factor

11. Conclusion
Composition of natural gas in gas fields in exploitation can deviate significantly compared to common composition, used for carbon dioxide emission factor calculation.
If ballast component, carbon dioxide, is not removed before combustion, it is emitted to atmosphere too.
Ballast component must be included in estimation of carbon dioxide emitted in processes of natural gas combustion
Method for calculation of overall emission factor is presented
Emission factor increases for more than 20% depending on ballast content