Calculated GHG emission is inconsistent with calculated CO2 emission

[ceilican]

[ceilican]

GHG emissions should be always larger than CO2 emissions, because GHG includes CO2 and other gases. This indicates that there might be bugs in the calculation of GHG emission.

[ceilican]

@PrateekGupta1509 , could you have a look on this issue?

[PrateekGupta1509]

@ceilican I will try to rectify this, I think there was inconsistency in the information on the website mentioned in issue #3. Also the server for the site is down, so I will look it into it if it up in next few days or go with some different data source to correct this.

[ceilican]

Ok!

[PrateekGupta1509]

Hi @ceilican! Sorry for the late communication, I had exams and my fest coming up so wasn't really active for a while.
The earlier website doesn't seem to host the information any longer. So I was thinking of using the same source we used for data released by the EPA source-link and shifting the GHG emission in terms of CO2e which is obtained by multiplying emission of each gas (CO2, CH4, N2O) by their respective global warming potential (GWP) and adding them up.
Also it might be better to shift the individual emission of CH4 and N2O in terms CO2e than in Kg/lbs as emission by these gases are better understood when compared with CO2.
The document above quotes:

Typically, greenhouse gas emissions are reported in units of carbon dioxide equivalent (CO2e). Gases are converted to CO2e by multiplying by their global warming potential (GWP).

So I think it might be better to make this change as a more standard approach. Let me know your take on this so I can make the required change.

[ceilican]

Hi @PrateekGupta1509 ! I agree with you. Feel free to proceed.

[PrateekGupta1509]

Hi @ceilican I found an archived version of the website we used as the source, and it clearly shows GHG emission in CO2e being less than the CO2 produced on combustion.

[ceilican]

Hi @PrateekGupta1509 ! That table shows CO2 emissions on combustion and life-cycle GHG emissions (measured in CO2e). Life-cycle emissions also take into account the emissions during production and transportation of the fuel, whereas on combustion emissions take only the emissions generated when the fuel is burned in the engine. For bio-fuels (like ethanol), the life-cycle emissions can be smaller than the emissions on combustion, because the production of bio-fuels absorbs CO2 from the atmosphere (e.g. in Brazil, ethanol is produced from sugar cane, and sugar cane absorbs CO2 when it grows). For fossil fuels (e.g. gasoline), the life-cycle emissions will always be greater than the emissions on combustion.

So:

1. there is still some inconsistency in our calculations, because the screenshot I included above shows CO2 emissions on combustion greater than life-cycle GHG emissions for gasoline, and this cannot be true.

2. We need to be more precise about whether we are talking about emissions on combustion or life-cycle emissions. (I have created issue Be more precise about CO2 emissions on combustion and total life-cycle CO2 emissions #125 for that.)

[PrateekGupta1509]

Fixed in #126 .