Coemissions of CO2 and H2O.
When burning oil and oil products in e.g. boilers and motors the resulting greenhouse gases emitted will be mainly CO2 and H2O.
If we for a rough calculation assume that the general “chemical oil formula” can be simply written CH2 the burning process can be written:
2 CH2 + 3 O2 = 2 CO2 + 2 H2O
and consequently equal numbers of CO2 and H2O molecules will be produced.
The numbers of molecules of CO2 and H2O can now be converted to CO2 equivalents as shown in the Background information section. The molecular weight of CO2 is about 44 and the molecular weight of H2O is 18. The “corresponding molecular weight” of CH2 would be 14. If we burn 1 kilogram of oil the emitted weight of CO2 there from will be about 3.14 kilograms of this gas and the emitted weight of H2O will be about 1.28 kilograms. The CO2 emission equivalents from 1 kilogram of oil will thus be 3.14 equivalents and the H2O emission equivalents will be about 1.28 X 40 = 51.2 equivalents.
About 95% of the greenhouse effect will thus depend on H2O and only about 5% on CO2.
If we now look at the emissions from the burning of natural gas and roughly and simply count on a chemical composition of: 85% methane, 10% ethane and 5% propane (and thereby disregard other small components like butane etc.) the burning process can simply be written:
For methane: 2 CH4 + 4 O2 = 2 CO2 + 4 H2O
For ethane: 2 C2H6 + 7 O2 = 4 CO2 + 6 H2O
For propane 2 C3H8 + 10 O2 = 6 CO2 + 8 H2O
If we now make the same calculations we will find that the CO2 emission equivalents will be about 3% and the H2O emission equivalents about 97 % of the greenhouse effect.
When burning oil, oil products and natural gas the greenhouse effect is up to 95 and 97 % caused by H2O (Water vapor) and only 3 to 5 % by CO2.
It is therefore misleading (as sometimes is done) to show pictures from the burning of oil, oil products and natural gas and state that these pictures show CO2 emissions when they show condensing water vapor. The two greenhouse gases are emitted simultaneously but H2O is visible and CO2 is invisible.
When burning coal of various qualities (from brown coal, lignite etc. to anthracite) - which have widely varying composition of many different chemical components - many and widely varying chemical compounds are formed (including the ashes). Most of the carbon, hydrogen and oxygen in the coal is coming from plant material. Disregarding SO2 etc. the main gaseous products formed are carbon dioxide and water vapor. The coal in situ (in the ground) also contains varying amounts of liquid water that adds to the water vapor emissions. If we in order to give an approximate estimate of the amount of water vapor that will be emitted when burning coal we now assume that its worldwide average water content in situ is 10 %. The carbon content of the coal in situ can also vary widely. If we now likewise assume that its worldwide average carbon content in situ is 60%, its amount of H is 5% and its amount of O is 10% we can calculate the total amounts of CO2 and H2O that have been emitted after burning:
1 kilogram of coal will give 2.2 kilograms of CO2 and 1 kilogram of H2O altogether (and most of the O required to be taken from the air). When burning coal the emissions of H2O will be responsible for abt. 95% of the warming effect and CO2 for abt. 5% after conversion to CO2 equivalents.
If we take a closer look at the points of emissions to the atmosphere the gas stream leaving the burning source has high concentrations there of both H2O and CO2. If we disregard the other components of the flue gases like N2, N compounds, Ar (argon) etc. originating from the air going into the burning process it will be of particular interest to study what happens to the two major greenhouse gases H2O and CO2 respectively during their travel through the atmosphere and through the troposphere. At the entrance into the atmosphere the two gases can be assumed to be well mixed (unless they have not formed complexes and/or clusters?) but then be little by little separated from each other as the gas stream becomes mixed with air and diluted. Also the difference in density between the two gases – the H2O being the lighter one – makes the H2O rise faster than CO2 as shown in the following table for all of the major greenhouse gases and for air including its other major components N2, O2 and Ar which do not add to the global warming at any important amount:
|grams/liter at 20° centigrade and 1 atm. pressure|
|N2||1,047(at 0° C)|
The Atmospheric Infrared Sounder (AIRS) onboard the NASA Spacecraft satellite has found that CO2 is not well mixed in the troposphere but is rather lumpy. A similar type of “lumpiness” for H2O can be seen by watching clouds.
Remark: Non-fossil plant material, like cellulose, lignin and other organic compounds (in wood, grass etc.) which are mainly built up by H-, O- and C-atoms, degrades by burning processes or rotting mainly to H2O and CO2. They are then generally returning as plant material by the photo synthesis process and therefore considered not to be responsible for the global warming effect or the climate change. They do not “take toll of” the deposits of coal, oil and natural gas in the Earth´s crust.