Environmental Engineering Reference
In-Depth Information
are or processed to produce secondary fuels (see
Table 2.1
). This is done either to facilitate
transport (e.g., liquefied gas) or to produce derivatives with different properties (e.g., coke
for metallurgy from coal, petrol from oil).
Table 2.1.
Primary and secondary fuels
Primary fuel
Secondary fuel
Origin
Mineral oil
Petrol, kerosene, diesel Fossil
Coal
Coke
Fossil
Wood
Charcoal
Renewable
Natural gas
Liquefied natural gas
Fossil
Bioethanol
ETBE
Renewable
Vegetable oil Biodiesel
Renewable
Combustion is a sequence of chemical reactions involving oxygen and a fuel, with
energy released in the form of heat and light. Unless it is interrupted, a combustion reaction
will continue spontaneously until all the chemical bonds are broken and the fuel is fully
consumed.
2.2 Alternative, Sustainable and Renewable Energy
Before we dive into the detail of how energy is generated, it is well to clear up possible
confusion about three similar but discrete terms. The term 'alternative energy' first came
into common use in the 1970s during the oil crises and simply denoted alternatives to oil.
At that time, the desire for such an alternative was driven more by political and economic
considerations than by environmentalism or concerns about sustainability. Therefore, coal
and natural gas, as well as nuclear, solar and wind power, were embraced as alternative
energy sources. More recently, the term 'alternative energy' has been used to mean all
alternatives to fossil fuels.
