B3.4.3 Biofuels

Question 1

What is the greenhouse effect?

Answer 1

Gasses in the Earth’s atmosphere trap some of the Sun’s heat and prevent it from escaping.

Question 2

What is global warming?

Answer 2

The increase of the Earth’s temperature due to the greenhouse effect.

Question 3

What are the two main greenhouse gasses that are increasing in our atmosphere?

Answer 3

• Carbon Dioxide

- Methane

Question 4

Why are carbon dioxide levels increasing?

Answer 4

• Humans are burning more fossil fuels
• Deforestation - less trees can absorb carbon dioxide
• Destroying peat bogs releases carbon dioxide

Question 5

Why are methane levels increasing?

Answer 5

• Humans are rearing more cattle
• Humans are planting more rice in paddy fields which rots to produce methane
• Humans are producing more waste which rots to produce methane

Question 6

How does an increase in greenhouse gasses cause global warming?

Answer 6

More greenhouse gasses means that a higher percentage of heat is absorbed and radiated back to earth instead of passing through the atmosphere, which means that the earth becomes warmer.

Question 7

What could an increase of the earth’s temperature by only a few degrees cause?

Answer 7

• Big changes in the Earth’s climate
• A rise in sea level
• Reduce biodiversity
• Changes in migration patterns, eg in birds
• Changes in the distribution of species.

Question 8

What is sequestering?

Answer 8

Carbon dioxide is absorbed by oceans, lakes and ponds to be locked away.

Dissolves in the water / photosynthesis by phytoplankton

Question 9

How much of the carbon dioxide released by humans is sequestered?

Answer 9

A quarter.

Question 10

Why is sequestering important?

Answer 10

It plays an important role in removing carbon dioxide from the atmosphere.

Question 11

Why are biofuels considered possible alternatives to fossil fuels for the future?

Answer 11

They are renewable and theoretically carbon neutral.

Question 12

How is ethanol produced?

Answer 12

Fermentation of sugar into ethanol and carbon dioxide in anaerobic conditions.

Question 13

Why is yeast required in the process to make ethanol?

Answer 13

Yeast contains natural catalysts for the making the process happen.

Question 14

What are the disadvantages of ethanol?

Answer 14

• The demand for crops means there is a greater demand for rainforest land
• More carbon dioxide is released by growing, harvesting, transporting and producing ethanol from crops than is absorbed by photosynthesis
• Cars need modification to use just ethanol

Question 15

What is the main gas found in biogas?

Answer 15

Methane

Question 16

How is biogas produced?

Answer 16

Anaerobic fermentation of carbohydrates in plant material or waste by bacteria.

Question 17

How is biogas generated on an individual scale?

Answer 17

• Carbohydrate containing materials are fed in
• Bacteria ferment the carbohydrate into biogas
• The methane is burned for cooking or heating
• The carbon dioxide produced from burning is absorbed by plants during photosynthesis

Question 18

What is the problem with producing biogas in a cold country?

Answer 18

The low temperatures are below optimum for the bacteria and so biogas is produced slower.

Question 19

What is the problem with producing biogas in a hot country?

Answer 19

The high temperatures are above optimum and cause the bacteria to begin to denature, slowing production.

Question 20

What is the solution for producing biogas in a hot or cold country?

Answer 20

Insulate the biogas generator - bury it.

Question 21

How is biogas generated on a commercial scale?

Answer 21

Biogas which is naturally produced in landfill sites can be with pipes and by covering the site. The biogas can then be used as a fuel.