6. Water released from fossil hydrocarbons
In the previous section, the discussion was based on a constant mass of
water on Earth dispatched as solid, liquid, vapor and clouds since
matter cannot escape to space. However, the combustion of all
hydrocarbons (oil, natural gas, and biomass) that generates hot
CO2 from the carbon content generates also water as hot
vapor from the atoms of hydrogen included in molecules. Once the heat
stored in these hot gases is transferred to the environment; the cooled
and condensed hot water constitutes a surplus that joins the existing
pool of liquid water. It is important to note that heat produced by
biomass burning is not compensated at the stage of biomass formation
because this renewal requires solar light at ambient and not heat.
Quantifying the amount of extra water from hydrocarbons is as difficult
as quantifying heats of e and rAHR-types. Nevertheless, estimates of the
overall consumptions (close but slightly less than productions when heat
release is concerned) of fossil oil and natural gas are available in oil
equivalents and provide means to estimate the surplus of water. Between
1870 and 2018, about 180 Gt of oil and 30 GToe of natural gas have been
extracted (Martin-Amouroux, 2015; BP, 2019) i.e. about 210 Gt of
hydrocarbons. To compensate the complex composition of oil and natural
gas, one can assume these fossil hydrocarbons, including methane
(CH4), composed of alkanes only, the general chemical
formula of which is CnH2n+2 reasonably
simplified to nCH2. Accordingly, 210 Gt of oil
equivalent contain c.a. 180 Gt of carbon and 30 Gt of hydrogen. From the
general equation CH2 + 3 O2 →
CO2 + H2O + heat, 14 g of hydrocarbon
(12 + 2) generates 44 g of CO2 (12 + 32) and 18 g of
water (16 + 2), both compounds being hot. One can deduced that 210 Gt of
hydrocarbons produced about 270 Gt of hot water in about 150 years. In
2018, 8 GT of oil equivalent of the hydrocarbon-type generated about
11.3 GT of hot water, an amount negligible compared with the heat
absorption capacity of 1,500 GT of disappeared ices and of surface water
evaporation.
According to section 5 and 6, the waste heat derived from the production
and the consumption of energy on Earth seems negligible today relative
to the radiative forcing estimate. However, this may change in the
future if the production of energy continues to grow while the
production of anthropogenic CO2 and the corresponding
radiative forcing are decreased as recommended to politicians by IPCC.