The combustion of the fuel should be at a moderate rate. The burning of the fuel should release heat in a controlled manner so that the fire neither dies nor explodes. The fuel should burn smoothly and sputter. Thus the rate of oxidation reaction of the fuel should also be moderate.
The fuel should also have a suitable ignition temperature. The fuel, of course, will only catch fire if its ignition temperature is reached. This means that if ignition temperature of the fuel is too low, then the fuel is not suitable as it will catch fire easily. If the ignition temperature is too high, then again it is not suitable, as reaching the ignition temperature to soon will not be practical. Thus the ignition temperature of an ideal fuel should not be too high or too low.
The environmental factors to consider are: the fuel should have low content of non combustible materials. Non combustible materials in a fuel are its impurities and when heated these impurities may cause pollution and give out undesirable harmful gases. Thus an ideal fuel should not pollute the air by emanating harmful gases. The fuel should not be more useful for other purposes other than its use as fuel. For instance, wood is a fuel but using wood means striping away forest cover, thus it is environmentally harmful to cut down trees. Hence it is not a suitable or ideal fuel. In the same way, coke is a good fuel but it is better that coke is used as a reducing agent in industrial. The gases which from should also be taken into account as many polluting gases can form.
In terms of economic costs: the fuel should be easily available and cost effective. Some fuels have all the characteristics of an ideal fuel like high calorific value, low pollution causing gases, etc. but these fuels can be very expensive. One example of this is high octane petrol. On this petrol, a car runs very efficiently. But the cost of this fuel is very high and is not readily available at petrol filling stations. High octane petrol is therefore not widely used. Thus an ideal fuel should be available easily and should also be cost effective.
The fuel should also be easy to store and transport. Fuels are extracted and purified in factories and have to be transported to either homes for domestic use or to industries for industrial use. Quite a large number of precautions have to be taken to handle, store and transport fuels. These are highly flammable substances. For example it is easier to transport gaseous fuels like LPG or methane in cylinders than to transport petrol or kerosene in tankers.
- Non-renewable energy sources