6. Water released from fossil hydrocarbons
In the previous section, the discussion assumed constant volume of water
dispatched between ice caps, floating ice and land ice since matter
cannot escape to space. However the combustion of all the hydrocarbons
(oil, natural gas, and biomass) generates hot CO2 from
the carbon content and hot water vapor from hydrogen. Once the heat
stored in these hot gases is transferred to the environment; the
generated cool water becomes surplus of water on Earth.
Quantifying the amount of such extra water is as difficult as
quantifying e and rAHRs. Nevertheless, data on the overall production of
fossil oil and natural gas are available 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. Based on the amount of water
released from 28,000 Gt of ice lost between 1994 and 2017, the estimated
270 Gt of extra water cumulated since 1870 corresponds to c.a. 1 year of
recent ice loss and, thus, it is rather small and negligible in terms of
ocean level rise. However this hot water inserted 2.3 KJ/Kg/°C of heat
in the environment, this heat being dispatched between biomass,
atmosphere, and liquid water. Whether this liberated water played a role
in the context of greenhouse gas is difficult to guess. Anyhow, the
release of hot water from the combustion of oil and natural gas could
become problematic if the production and the consumption of energy,
fossil or not, continue to grow in parallel to the growth of the
mammalian population (Zou et al., 2016).