Energy and Electricity - Introduction to Carbon Capture and Sequestration - page 6

3. How much CO 2 comes from one power plant?
4. How much CO 2 can we capture?

Current CO 2 production
The most important source of atmospheric CO 2 is the burning of fossil
fuels as part of our energy consumption. In the literature one can find
many statistics on energy consumption. Figure 1.2.1 is one example in
which the total world energy consumption is divided according to its dif-
ferent sources [1.2]. This graph illustrates the importance of fossil fuels:
over 80% of the energy sources we use emit CO 2 . In addition, we see
that the total energy consumption has doubled during the last 30 years.
The total energy production is given in Mtoe , which stands for 10 6
tonnes of equivalent oil, i.e., the produced energy is equivalent to the
energy released by burning 10 6 tonnes (10 9 kg) of oil (in SI units 1 toe =

42 GJ). The energy content of different fuels is different and the conver-
sion to Mtoes allows us to compare them. Table 1.2.1 shows how many
tonnes of CO 2 are produced by the combustion of three types of fossil
fuels due to their different stoichiometries. These differences can be
understood if we look at the basic combustion equation:

y y

Ê ˆ

CH ++ x O → x CO + HO

Á ˜

xy 2 2 2

Ë ¯

4 2

Natural gas has a much higher hydrogen content compared to coal, and
therefore produces less CO 2 per tonne of fuel.
Figure 1.2.1 shows that the 2011 global energy consumption is more
than 10,000 Mtoe. If all that energy were from oil, we would annually pro-
duce approximately 30,000 10 6 tonnes of CO 2 . Often, we express this

quantity in terms of gigatonnes of carbon (Gt C), which is 8.2 Gt C. The
real CO 2 production is higher, as the different fossil fuels do not produce
identical amounts of CO 2 per unit energy. If we correct for these differ-
ences, we obtain the result that our current global energy consumption
produces over 31,000 M tonne (31,000,000,000,000 kg) of CO 2 each year.
The production of cement also produces significant amounts of CO 2
that is emitted to the atmosphere. The historical CO 2 emission data from
different sources are given in Figure 1.2.2 [1.3].

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