Comments on: What are the co2 emissions (in lbs per gallon) of a CNG bus? http://london-lez.org/co2-emissions/what-are-the-co2-emissions-in-lbs-per-gallon-of-a-cng-bus Sat, 19 May 2012 16:31:53 +0000 http://wordpress.org/?v=2.7 hourly 1 By: Nata T http://london-lez.org/co2-emissions/what-are-the-co2-emissions-in-lbs-per-gallon-of-a-cng-bus/comment-page-1#comment-4217 Nata T Sun, 29 Nov 2009 22:18:59 +0000 http://london-lez.org/co2-emissions/what-are-the-co2-emissions-in-lbs-per-gallon-of-a-cng-bus#comment-4217 CO2 is released when burning methane CH4 at a rate proportionate to the number of Carbons on each side of the Chemical balance of CH4 + 2 *O2 = CO2 + 2 *H2O or 1 mole of CH4 makes 1 mole CO2. 1 mole (lb-mole) of CH4 weights 16 pounds and will make 44 pounds of CO2 or 2.75 pounds CO2/lb CH4. As stated above you have to define a gallon of CNG at a set pressure and temperature. Now lets look at your gasoline value. Gasoline is a whole bunch of different molecules but, we can assume gasoline is Octane C8H18. C8H18 + 12.5 *O2 = 8 *CO2 + 9 * H2O, so 114 pounds of octane will make 352 pounds of CO2 .or 3.08 pounds of CO2 per pound of C8. since all hydrocarbons have about the same energy per pound. methane will produce 2.75/3.08 or 90%. If you do take into account the slight BTU/lb difference, it works out that CNG produces 18% less CO2 per energy unit than gasoline.<br><b>References : </b><br> CO2 is released when burning methane CH4 at a rate proportionate to the number of Carbons on each side of the Chemical balance of

CH4 + 2 *O2 = CO2 + 2 *H2O or 1 mole of CH4 makes 1 mole CO2.

1 mole (lb-mole) of CH4 weights 16 pounds and will make 44 pounds of CO2 or 2.75 pounds CO2/lb CH4.

As stated above you have to define a gallon of CNG at a set pressure and temperature.

Now lets look at your gasoline value. Gasoline is a whole bunch of different molecules but, we can assume gasoline is Octane C8H18.

C8H18 + 12.5 *O2 = 8 *CO2 + 9 * H2O, so 114 pounds of octane will make 352 pounds of CO2 .or 3.08 pounds of CO2 per pound of C8.

since all hydrocarbons have about the same energy per pound. methane will produce 2.75/3.08 or 90%. If you do take into account the slight BTU/lb difference, it works out that CNG produces 18% less CO2 per energy unit than gasoline.
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]]> By: Breath on the Wind http://london-lez.org/co2-emissions/what-are-the-co2-emissions-in-lbs-per-gallon-of-a-cng-bus/comment-page-1#comment-4216 Breath on the Wind Sun, 29 Nov 2009 22:04:59 +0000 http://london-lez.org/co2-emissions/what-are-the-co2-emissions-in-lbs-per-gallon-of-a-cng-bus#comment-4216 CNG or compressed natural gas, (CH4) is a compressed gas and not a liquid. It is not typically measured in gallons. Liquids that are stable at room temperature and pressure are measured in gallons. LNG (liquid natural gas) is a liquid because it has been compressed and cooled. In this article: http://www.triplepundit.com/2006/11/askpablo-clean-natural-gas/ you will find a very careful discussion of gasoline and CNG emissions. It turns out that CNG produces less particulate matter and about 70% of the CO2 that would be required from a gasoline powered vehicle.<br><b>References : </b><br> CNG or compressed natural gas, (CH4) is a compressed gas and not a liquid. It is not typically measured in gallons. Liquids that are stable at room temperature and pressure are measured in gallons. LNG (liquid natural gas) is a liquid because it has been compressed and cooled.

In this article: http://www.triplepundit.com/2006/11/askpablo-clean-natural-gas/ you will find a very careful discussion of gasoline and CNG emissions. It turns out that CNG produces less particulate matter and about 70% of the CO2 that would be required from a gasoline powered vehicle.
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]]> By: Adam http://london-lez.org/co2-emissions/what-are-the-co2-emissions-in-lbs-per-gallon-of-a-cng-bus/comment-page-1#comment-4215 Adam Sun, 29 Nov 2009 21:15:59 +0000 http://london-lez.org/co2-emissions/what-are-the-co2-emissions-in-lbs-per-gallon-of-a-cng-bus#comment-4215 It depends on the pressure of the CNG. You see, a liquid like gasoline has a certain number of molecules in each gallon, which burn to produce a certain quantity of CO2. However for a gas like CNG, the number of molecules in a gallon is dependent on the pressure of the system. A highly pressurized system will contain more fuel per gallon and will emit more CO2 per gallon.<br><b>References : </b><br> It depends on the pressure of the CNG.

You see, a liquid like gasoline has a certain number of molecules in each gallon, which burn to produce a certain quantity of CO2.

However for a gas like CNG, the number of molecules in a gallon is dependent on the pressure of the system. A highly pressurized system will contain more fuel per gallon and will emit more CO2 per gallon.
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