I.2. The CO2 as a main greenhouse gas

The greenhouse effect is connected with the increase in average temperature on Earth as a result of disruptions in the exchange of heat between the Earth and the upper layers of the atmosphere[3]. The direct cause is the accumulation in the atmosphere following gases:

• vapor water,
• carbon dioxide,
• nitrogen oxides,
• methane.

A significant amount of these gases get into the atmosphere as a result of industrial activities, especially at:

- steel mills,

- power plants,

- electro-heating plants,

- incineration plants, etc.

Carbon dioxide is formed primarily by the combustion of fossil fuels but also formed in natural processes, such as respiration, putrefaction. The gas is absorbed by plants during assimilation in plants thus are involved in regulating the amount of carbon dioxide in the atmosphere. Large amounts of CO₂ are stored by water of seas and oceans [4].

Figure 1, presents the share of individual greenhouse gases having a significant role in global warming. Carbon dioxide is the main greenhouse gas.

Figure 1: Share of individual greenhouse gases in global warming. Other category includes halons, tropospheric ozone and vapor water in the atmospher [5].

The amount of carbon dioxide emitted during the combustion is directly related to the content of the element in different chemical compounds found in organic composition of the fuel. In the high-methane gas the value of the H:C ratio is assumed to be equal to 4, in fuel oil, to be equal to 2.2 and in coal to be equal to ca. 0.5.

Thus as from the data listed in Table 1, emissions from combustion of fossil fuels depend on the type of the fuel natural gas leads to almost the emissions that are almost half of these connected with the burning of coal and about 25% smaller than the emissions accompanying the combustion of petroleum oil [7].

Table 1: Emission of CO₂ depended of the kind of fuel (Source: Ruhrgas AG, EUROGAS, OECD/IEA, CIE, WE_CO2(max) calculated for Polish sector) [6].

Emission indicator	Kind of fuel
	Lignite	Hard coal	Heavy fuel oil	Diesel oil	Natural gas
Emission of CO2
kg CO2/kWh	0,4	0,33	0,28	0,26	0,2
kg CO2/GJ	102	91,3	78,5	73,3	55,9
Emission of C, kg C/GJ	ok.. 31	25,8	20	19,9	15,3