Q9. Fossil fuels are used to generate electricity, but over half of the world's population uses biomass as a fuel.

(a) What is 'biomass'?

Answers must give a definition of biomass and not just provide examples. If they wanted examples they word word the question differently.

Biomass is fuel material that comes from living things. It is primarily plant material. It is also waste matter from living animals or the dead form of them.

1 mark

(b) Biomass and fossil fuels are both energy resources. What is the original source of this energy?

The Sun's light is the original source of these energy forms. Both are formed into original material by photosynthesis, sunlight combining carbon dioxide and water into plant matter.

1 mark

(c) Give the names of three fossil fuels which are often burned to generate electricity.

Coal, oil and natural gas (or methane).

1 mark

(d) Fossil fuels are often described as non-renewable energy resources. Explain why they are called 'non-renewable'.

Non-renewable resources cannot be naturally replaced in a small enough timescale for us to have an unlimited supply. When we have run out, it will take natural processes millions of years to form them again.

Do not accept 'they cannot be used again' - no fuel can be 'used again'. After it has been burnt you need a fresh supply.

1 mark MAX

(e) There are advantages and disadvantages of burning different fuels.

(i) Give one advantage of using biomass rather than fossil fuel as an energy resource.

any one from:

• it is renewable
• it is widely available accept 'you can grow more of it'
• it will conserve fossil fuel supplies

do not accept 'it is cheaper to produce'

1 mark

(ii) Give one advantage of using fossil fuel rather than biomass as an energy resource.

any one from

• it is a more concentrated fom of fuel energy- it contains more energy per unit mass
• it is more suitable for use in vehicles
• it can be transported more easily

1 mark

(iii) Give one disadvantage of using both fossil fuel and biomass.

any one from

• they release pollution into the atmosphere
• they release greenhouse gases

Properly managed biomass production maintains a balance of carbon dioxide in the atmosphere - as the CO₂ it releases it took from the atmosphere when being grown. However, biomass 'farming' often operates on land that has been cleared of vegitation that originally would have retained more CO₂ within the vegitation. It is not simple math to calculate the effect growing fuel crops has!

Fossil fuels, on the other hand, when burnt release CO₂ that has been trapped out of the carbon cycle for a long while. Over the past couple of centuries we have released vast amounts of carbon back into the cycle and that has disturbed the balance of gases in our atmosphere. Fossil fuels do more damage to the atmosphere balance than biomass does.

1 mark

Maximum 7 marks