Answers to AQA GCSE Biofuels

Practice Questions

1.Both coal and wood come from living organisms, but only wood is classed as a biofuel. Explain why wood is a biofuel, but coal is not.

Coal is formed over millions of years, so it is not a biofuel. Wood comes from trees which is a recently living organism, so it is a biofuel.

2.Suggest why it is important to maintain the temperature in biogas generator.

Bacteria use enzymes to carry out decomposition. If the temperature is too low, then rate of reaction is too slow for decomposition to occur. If the temperature is too high, bacteria are killed and their enzymes are denatured.

3. What is the environmental advantage of using biogas to heat our homes compared to natural gas?

When biogas and natural gas are burnt, they both produce carbon dioxide. However, the biogas is carbon neutral because the next set of crops that are grown to provide the animal feed will take in carbon dioxide. 

4.Explain why ethanol produced by fermentation is classed as carbon neutral.

Sugar cane that is grown to produce the ethanol through fermentation will take in carbon dioxide. The amount of carbon dixoide that is produced by burning the ethanol, is equal to the amount of carbon dioxide that is absorbed by the sugar cane during growing process.