Resource 4: Properties of common fuels
Background information / subject knowledge for teacher
Properties of common fuels
Your students will have come across various different fuels (although they might need some prompting). There is no ‘ideal’ fuel. Different fuels are better for different jobs. Liquid fuels are easy to light, but are therefore quite dangerous. Charcoal is quite difficult to light, but burns with a very hot flame. Each fuel has advantages and disadvantages.
Here are some questions that you could ask your students about the fuels that they are familiar with:
- What would the fuel be used for?
- Where does the fuel come from?
- Is the fuel cheap or expensive compared with others?
- Is the fuel easy to light?
- When we have used all the fuel that is available can we replace it?
- Does the fuel produce lots of smoke and soot?
- Does the use of the fuel affect the environment? If yes, how?
Here is some background information about some common fuels
| Fuel | Global reserves | Approximate energy content/ kJ g–1 | Effect on environment | Practical and safety issues | Renewable? |
|---|---|---|---|---|---|
| Wood | Difficult to put a figure on this but if the forests that provide wood fuel are re-planted at the same rate as they are cut down, then such fuel use should in principle be sustainable. | 0.15 | When forests are managed sustainably in this way the CO2 absorbed in growing replacement trees should equal the CO2 given off when the original trees are burned. The incomplete combustion of wood can release a mixture of greenhouse gases with a greater overall global warming effect than can be offset by the CO2 absorbed in growing replacement trees. Wood burning processes need to be made as efficient as possible. | Easy to light Safe to store Ash is produced | Renewable |
| Petrol/ diesel/ kerosene (crude oil) | Approximately 30 more years | 46 | Produces carbon dioxide gas, which contributes to the greenhouse effect. The other major atmospheric pollutants are oxides of nitrogen, which contribute to acid rain; carbon particulates and unburned hydrocarbon fuel. | Easy to light Safety issues – has to be stored carefully | Non-renewable |
| Coal | Approximately 190 more years | 35 | Contains sulfur as an impurity. This means that sulfur dioxide will also be emitted to atmosphere, which contributes to acid rain. | Hard to light Safe to store Produces ash | Non-renewable |
| Natural gas (methane) | Approximately 50 more years | 54 | Produces carbon dioxide and carbon monoxide. | Easy to light Safety issues No ash, but can produce carbon monoxide if not installed correctly | Non-renewable |
| Biofuels | A major source of bioenergy is alcohol (ethanol) produced by fermenting sugar cane or maize. The alcohol is often blended with conventional petroleum to form a mixture known as ‘Gasohol’. Also ‘biogas’ (methane) produced during the anaerobic respiration of manure and biological waste. | 30 (ethanol) | Both produce carbon dioxide and water vapour , which are greenhouse gases. However, biofuels are claimed to have a ‘neutral carbon footprint’ because, theoretically, the plants grown to produce them absorb as much carbon dioxide from the atmosphere as is emitted when the fuels is burned. | Easy to light Safety issues No ash or residue | Renewable |
40 (biogas is approximately 50% methane) | Renewable | ||||
| LPG (liquid petroleum gas) | Approximately 30 more years | 48 | Produces greenhouse gases when burnt. | Easy to light Difficult to store – stored under pressure No ash or residue | Non-renewable |
Resource 3: Brainstorming
