Question

2. Based on the mass of methane that was combusted, how much energy was released in GJ? Assume the energy content for natural gas is 55 MJ/kg.

6.4117 x 10¹¹ kg of methane is combusted = 6.4117 x 10¹¹ x 55 MJ = 352.6435 x 10¹¹ MJ

352.6435 x 10¹¹ MJ = 352.6435 x 10¹¹ x 0.001 GJ = 352.6435 x 10⁸ GJ of energy was released.

3. Based on the mass of methane that was combusted, what mass of CO₂ was released?

16 g of Methane produces 44 g of Carbon Dioxide

1 kg of methane will produce = 0.044/0.016 kg of CO2

0.016 kg of Methane produces 0.044 kg of CO2

6.4117 x 10¹¹ kg of methane produces = 0.044/0.016 x 6.4117 x 10¹¹ kg of CO2 = 17.6322 x 10¹¹ kg of CO2.

4. Based on the mass of methane that was leaked, determine the equivalent mass of CO₂ that this represents? Assume a 100 year time frame.

0.1983 x 10¹¹ kg of methane produces = 0.044/0.016 x 0.1983 x 10¹¹ kg of CO2 = 0.5453 x 10¹¹ kg of CO2.

The equivalent mass of CO2 that it represents is 0.5453 x 10¹¹ kg.

5. Now calculate a CO₂e emission factor by dividing the mass of CO₂e in kg (sum of #3 and #4) and dividing by the energy released by combusting the natural gas in GJ (#2).

6. Compare this to the CO₂ emission factor for natural gas that ignores leakage (factor is 50 kg/GJ).

Answer 1

2) The energy content of natural gas is 55MJ/kg.

Mass of methane gas combusted = 6.4117*10¹¹ kg.

Therefore, energy released = (6.4117*10¹¹ kg)*(55 MJ/kg)

= 3.526435*10¹³ MJ

= (3.526435*10¹³ MJ)*(1 GJ)/(1000 MJ)

= 3.526435*10¹⁰ GJ

≈ 3.5264*10¹⁰ GJ (correct to five sig figs, ans).

3) 16 g methane gives 44 g.

Therefore, mass of CO₂ released from 6.4117*10¹¹ kg methane

= (6.4117*10¹¹ kg methane)*(1000 g methane)/(1 kg methane)*(44 g CO₂)/(16 g methane)*(1 kg CO₂)/(1000 g CO₂)

= 1.7623175*10¹² kg

≈ 1.7623*10¹² kg (correct to five sig figs, ans).

4) Mass of methane gas leaked = 0.1983*10¹¹ kg

Mass of CO₂ equivalent to 0.1938*10¹¹ kg methane

= (0.1983*10¹¹ kg methane)*(1000 g methane)/(1 kg methane)*(44 g CO₂)/(16 g methane)*(1 kg CO₂)/(1000 g CO₂)

= 5.45325*10¹⁰ kg

≈ 5.4532*10¹⁰ kg (ans).

5) Total mass of CO₂ = (1.7623*10¹² + 5.4532*10¹⁰) kg = 1.816832*10¹² kg.

Energy released = 3.5264*10¹⁰ GJ.

Therefore,

CO₂ emission factor = (mass of CO₂ released)/(energy released)

= (1.816832*10¹² kg)/(3.5264*10¹⁰ GJ)

= 51.52087 kg/GJ

≈ 51.5 kg/GJ.

6) The CO₂ emission factor for natural gas, ignoring leakage, is 50 kg/GJ. When we consider leakage, the CO₂ emission factor turns out to be 51.5 kg/GJ.

The percentage error is given as (considering without leakage as the true value)

=│(50 kg/GJ) – (51.5 kg/GJ)│/(50 kg/GJ)*100

= 3.0

The percentage error is 3.0% which is within the limits of experimental error (usually 5% error margin is allowed).