Muhammad Ery Wijaya 6/3/2009

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Dear Dr. Charlie,

I got problem when I want to change chemical composition of coal according to Indonesian coal. Actually, if I change the composition of coal, it should affect to the emission that caused by coal, but it doesn't happen in my LEAP. Could you tell me how to solve it?


Thank you,

Regard,

Wijaya

Charlie Heaps 6/3/2009
 

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> I got a problem when I want to change chemical composition of coal according to Indonesian coal. Actually, if I change the composition of coal, it should affect to the emission that caused by coal, but it doesn't happen in my LEAP. Could you tell me how to solve it?

Whether or not LEAP's environmental results are effected by edits to the chemical composition of fuels will depend on the formula you have used to specify your emission factors in LEAP.

For CO2 emissions most of the IPCC Tier 1 emission factors in LEAP are specified something like this...

25.8 * fractionoxidized * (co2/c) [Tonne/TJ]

The 25.8 value is the amount of carbon present per TJ of fuel (in this case coal). "FractionOxidized" is a property of the fuel indicating how much of the carbon in the fuel is oxidized (turned into CO2) and the two constants for CO2 and C are simply the molecular weight of carbon dioxide and carbon (roughly 44/12) - used to translate the factor from carbon into CO2.

In this form of the equation the emissions do not directly depend on the carbon content of the fuel, so changing the carbon content in the General:Fuels screen will NOT affect the emissions calculated by LEAP (as you note). However, because the factors are specified in terms of tonnes/TJ the actual emissions calculated will be fairly accurate so long as the energy calculations themselves are correct - since the energy content of the fuel is, to a first approximation, proportional to the carbon in the fuel.

An alternative approach would be to specify the CO2 emissions factor in a way that directly refers to the fuel's carbon content using a formula like this:

[CO2 Emissions =] CarbonContent * FractionOxidiuzed * (CO2/C)

If you use this approach, be sure to set the emission factor units to Tonnes/Tonne (of fuel burnt).

You can see a variation on this approach in the emission factors for SO2, which look like this...

[SO2 Emissions =] sulfurcontent*(1-sulfurretention)*(so2/s)

Again, this formula references the sulfur content of the fuel and the amount of sulfur retained (not emitted), both of which are properties of the fuel.

Two important points to bear in mind:

1. The energy content and density properties of fuels are used when converting inputs between mass, volume and energy units. If you enter your data in analysis view in mass or volume units (e.g. tonnes of coal, barrels of oil). The fuel's properties will then be used to translate your data into GJ terms for LEAP's calculations. LEAP does all its internal calculations in GJ by the way, although you can report results back in any energy unit. So...if you enter data in mass or volume terms but later you alter the properties of the fuel, bear in mind that this will also alter the energy data in your LEAP data set. If all of the data you enter in LEAP is in energy terms (GJ, TOE, kWh, etc.) this will not be an issue.

2. One weakness of the way LEAP works at present is that fuel properties are all static. You cannot specify how the sulfur, energy and carbon content of fuels change over time. In some places (for example china) the sulfur content of coal has changed significantly in recent decades. You can work around this weakness by putting a dynamic function (e.g. an interpolation function) into your emission factor equation if this is a significant issue in your analysis.

Finally, note that you can also specify emission factors per unit of fuel produced (not consumed). For example, you may find data specifying emissions per kWh of electricity generated. I prefer NOT to use this approach since emissions depend primarily on the type of fuel being burnt.

I hope this helps - sorry for such a long reply!

Charlie