Biofuels

Question 1

Why should biofuels be used instead of fossil fuels?

Answer 1

They are carbon neutral

Question 2

What are many biofuels made using?

Answer 2

Microorganisms

Question 3

How can biofuels be made?

Answer 3

Fermentation of natural products, often waste products

Question 4

What is fermentation?

Answer 4

When bacteria or yeast break sugars down by anaerobic respiration.

Question 5

How is ethanol made?
How? (simple, what makes what by what)
What is the ethanol distilled from?

Answer 5

Anaerobic fermentation of sugar
Yeast makes ethanol when they break down glucose by anaerobic respiration
The yeast and remaining glucose, to separate it from these

Question 6

Describe the word equation for ethanol production….

Answer 6

Glucose - (to, =) Ethanol + CO2 + ENERGY

Question 7

What glucose sources can be used to make ethanol? (2)

Answer 7

Sugar cane juices

Glucose derived from maize starch by the action of carbohydrase

Question 8

What are cars adapted to run on in countries like Brazil?

Answer 8

A mixture of petrol and ethanol, ‘gasohol’

Question 9

What is biogas made from?

Answer 9

Anaerobic fermentation of waste material

Question 10

What is the composition of biogas?

Answer 10

70% methane 30% CO2

Question 11

How is biogas produced?

Answer 11

Using lots of different microorganisms
They ferment plant and animal waste which contains carbohydrates
Sludge waste, from sewers or sugar factories, is used to make biogas on a large scale

Question 12

What is biogas made in?

Answer 12

In a simple fermentor called a digester or generator

Question 13

How are the microorganisms in the generator kept respiring?

Answer 13

They are kept at a constant temperature

Question 14

What is the storage problem with biogas?

Answer 14

It can’t be stored as a liquid as it needs to high a pressure. So it must be used straight away for heating or lighting, cooking or to power a turbine to generate electricity.

Question 15

How are biogas generators being used?

Answer 15

Large scale biogas generators are being set up in a number of countries
Small biogas generators are making enough to power villages or for a family to use in their cooking stoves and for heating and lighting.

Question 16

What can be used to make biogas locally? (3)

What can the byproducts of fermentation be used for?

Answer 16

Human or animal waste, food waste, all can be digested by bacteria to produce biogas.
To fertilise crops and gardens

Question 17

What are the two main types of biogas generators?

Answer 17

Batch generators

Continuous generators

Question 18

What are batch generators?

How is the biogas made? (3 stages (simple))

Answer 18

They make biogas in small batches.
They’re manually loaded up with waste,
This is left to digest
The byproducts are cleared away after each session.

Question 19

What are continuous generators?
How is the biogas made? (2 stages (simple))
What are they more suited to?

Answer 19

Make biogas all the time
Waste is continuously fed in
So biogas is produced at a steady rate
Large scale biogas production

Question 20

Describe the basic features all biogas generators must have…
Describe what the picture would look like….
Container
Inlet
Outlet
Tap
Top

Answer 20

An inlet for waste material to be put in
An outlet for the digested material to be removed through
An outlet so that the biogas can be pumped to where it is needed
A round container underground. On the left is a tube from above ground going into the solution. On the right is the outlet tube stemming from halfway down the solution. There is an opening at the top of the ball, with a seal and a tube coming out and going away above ground to a factory. The top of the container is round for maximum storage of the gas. (Solution is waste material)

Question 21

What are the four factors that need to be considered when designing a generator? PECC

Answer 21

Position
Efficiency
Cost
Convenience

Question 22

What needs to be considered surrounding the cost of a biofuel generator?
Inlet, outlet

Answer 22

Continuous generators are more expensive than batch because they require mechanical pumping of the waste into the generator, and the mechanical removal of the digested material all the time.

Question 23

What needs to be considered surrounding the convenience of a biofuel generator?

Answer 23

Batch generators are less convenient because they have to be continually loaded, emptied and cleaned

Question 24

What needs to be considered surrounding the efficiency of a biofuel generator?
Temp
Loss

Answer 24

Gas is produced most quickly at 35c
If the temp falls production will be slower
Generators in some areas will need insulated or to be kept warm, e.g solar heaters
The generator shouldn’t have any leaks or gas will be lost

Question 25

What needs to be considered surrounding the position of a biofuel generator?

Answer 25

The waste will smell during delivery so generators should be situated away from homes
It is best that the generator be closed positioned next to the waste source.
To keep it insulated they could be placed underground, this also reduces the smell.

Question 26

Why are biofuels greener than fossil fuels?

So they are…

Answer 26

They release the same CO2 they absorbed, none is locked away, none is produced.
Carbon neutral.

Question 27

Why are they good, to do with the rain?

Answer 27

They don’t produce significant amounts of sulphur dioxide or nitrogen oxides that cause acid rain

Question 28

Why is biogas good for the reduction of release of methane gas into the atmosphere?

Answer 28

As a gas responsible for global warming, it’s great that the untreated farmyard waste (manure) which gives off methane, it burnt instead of using it as fertiliser, so no methane is released into the atmosphere.

Question 29

What is an economic advantage for using biofuel?

Answer 29

The reactants are cheap and readily available

Question 30

What is one social positive for biogas?

Answer 30

Women in rural areas have to spend hours a day collecting fire wood, so biogas saves them energy, time and from boredom.

Question 31

What is one massive positive human impact of biogas generators?

Answer 31

It removes waste that would otherwise lie around causing disease and polluting water supplies.

Question 32

Describe the biogas cycle at a house with a cow and a field….

Answer 32

Grass absorbs CO2 from the atmosphere
The cow eats the grass, carbon is absorbed.
The cow poops, the waste is fermented in the generator
It’s burnt in the over in the house, and the CO2 is released back into the atmosphere.
The CO2 is reabsorbed by the grass and the process repeats.