1.9 Energy From Biomass

Question 1

Explain the term Biomass; {1}

Answer 1

Biomass is a general term for material derived from plants or animals. {1}

Question 2

Define the term Biomass; {1}

Answer 2

Biomass is a general term for material derived from plants or animal manure.
{1}

Question 3

Define what is meant by the term biomass. {1}

Answer 3

Material that is derived from growing plants or animal manure. {1}

Question 4

Biomass can be used as a fuel. Explain what is meant
by the term biomass. {2}

Answer 4

Biomass is material derived from growing plants or from animal manure.

Question 5

Identify another category of biomass apart from
woodchip. {1}

Answer 5

Ant one from;
* Organic materials. {1}
* Agricultural crops. {1}
* Agricultural and municipal wastes. {1}

Question 6

Wood is one example of biomass that can be used as a fuel source. Most of the
energy obtained from biomass is through combustion.
(i): Define the term biomass. {1}
(ii): State another categorised type of biomass, part from wood. {1}

Answer 6

(i): Biomass is material derived from growing plants or from animal manure.
(ii): Any one from: organic materials [1]
agricultural crops [1]

Question 7

Identify two crops that are commercially grown to
produce biomass. {2}

Answer 7

Any two from the following;
• Willow
• Poplar
• Elephant grass
• Maize
• Sugar Cane

Question 8

Give an example of a crop that can be commercially grown
to produce biomass. {1}

Answer 8

Any one of the following;
Willow / poplar / elephant grass / maize / sugar cane.

Question 9

Briefly describe the global debate that surrounds farmers growing crops for energy
{2}

Answer 9

Answer to outline the global debate around ‘food versus fuel’. {1}
Global population increasing at a dramatic rate. This is increasing demand for
food for basic human survival. Should farm land be used to grow energy crops
instead of food produce? {1}

Question 10

Identify two different advantages of replacing coal with
biomass at this power station. {2}

Answer 10

Any two of the following;
• Biomass fuel is a renewable energy source / can be replaced in a human
lifetime whereas coal takes millions of years to form / cannot be replaced in
a human lifetime.
• Combustion of biomass contributes much less to atmospheric carbon dioxide
levels (than coal / fossil fuels) / is carbon neutral / does not contribute (as
much) to global warming.

Question 11

State one disadvantage of converting all six units to burn
biomass instead of coal. {1}

Answer 11

Any one of the following;
• Biomass is more expensive to use compared to coal.
• Biomass is less efficient compared to fossil fuels.
• Biomass requires more land for production.

Question 12

Biomass is another alternative to fossil fuels.
(i): State two advantages of using biomass as an alternative to fossil fuels.
(ii): State two disadvantages of using biomass as an alternative to fossil fuels.
{2}

Answer 12

(i): Any two from:
Lower fossil fuel dependency [1]
Renewable [1]
Lower greenhouse gas emissions [1]

(ii): Any two from:
Requires significant quantities of land [1]
Has a lower energy density than fossil fuels/larger quantities required [1]
Biomass power plants have higher set-up costs [1]

Question 13

State the typical (%) of energy from combustion that is
obtained from biomass. {1}

Answer 13

% in the range of 90% {1}

Question 14

State the main process used to obtain energy from biomass.
{1}

Answer 14

Combustion / burning. {1}

Question 15

State the percentage of all energy from biomass obtained by combustion. {1}

Answer 15

Greater than 90%

Question 16

Explain the term energy density. {1}

Answer 16

Energy density is the amount of energy stored in a given system or region or
space per unit volume or mass. {1}

Question 17

State two properties which could be compared and
contrasted when assessing different types of woodchip for use as biomass fuel.
{2}

Answer 17

Any two of the following;
• Moisture content.
• Porosity,
• Bulk density
• Energy density

Question 18

Woodchip is a form of biomass that can be commercially
produced. Explain the effect of moisture content on one property of woodchip
fuels. {2}

Answer 18

Higher moisture content results in woodchip with lower energy density {1}. As
energy must be used to evaporate the water before combustion occurs {1}.

Question 19

List two properties of woodchip which are important in determining its
effectiveness as a fuel. {2}

Answer 19

Any two from;
* Percentage moisture content {1}
* Calorific value / energy density {1}
* Particle size {1}

Question 20

Discuss how the properties of woodchip affect the energy density. You must
refer to the properties of woodchip from the table above.
1: ________________ {2}
2: ________________ {2}

Answer 20

1: Percentage moisture content. Higher moisture content results in woodchip
with lower energy density as energy must be used to evaporate the water
before combustion occurs. {2}
2: Bulk density. Higher bulk density results in woodchip with higher energy
densities as this woodchip has more material per unit volume. {2}

Question 21

Outline the process of gasification in relation to
biomass. {2}

Answer 21

Gasification is a process that converts organic or fossil based carbonaceous
materials into carbon monoxide, hydrogen and carbon dioxide. {1}
This is achieved by reacting the material at high temperatures, without
combustion, with a controlled amount of oxygen and / or steam to produce
syngas. {1}

Question 22

Describe the process of gasification of biomass. {3}

Answer 22

Biomass is converted into a mixture of carbon monoxide {1}
And hydrogen {1}
Commonly known as syngas. {1}

Question 23

Biomass can be converted into syngas.
Name the two main gases present in syngas. {2}

Answer 23

Carbon monoxide {1}
Hydrogen {1}

Question 24

(i): Biomass can be used to produce a mixture of carbon monoxide and
hydrogen gas. {1}
(ii): {2}
Explain how biomass is converted into carbon monoxide and hydrogen.

Answer 24

(i) Syngas {1}
(ii): Biomass is heated in the presence of oxygen and steam. This causes the
biomass to break down into a mixture of carbon monoxide and hydrogen gas.
This process is called gasification. {2}

Question 25

State three applications in which the main product of the {3}

Answer 25

Any three from the following; • Used in the production of ammonia. {1} • Used in the production of methanol. {1} • Used as an intermediate in producing synthetic petroleum. {1} • Or can be used as lubricant in chemical processes. {1} • Syngas is combustible and often used as a fuel of internal combustion engines. {1}

Question 26

Certain types of biomass can undergo anaerobic digestion. Describe the process of anaerobic digestion. {2}

Answer 26

Anaerobic digestion is a biological process that results in the breakdown of organic matter {1} by naturally occurring bacteria in an environment that has an absence of oxygen {1}.

Question 27

Biogas is a mixture of gases produced by the anaerobic digestion of certain types of biomass. (i) Define the term anaerobic digestion. {2}

Answer 27

The biological breakdown of organic matter {1} in the absence of oxygen {1}.

Question 28

(ii) List the two main gases that are present in biogas. {2}

Answer 28

Methane {1} and Carbon dioxide {1}.

Question 29

Name the main product of anaerobic digestion and state its use. Product. {1} Use. {1}.

Answer 29

Product – Methane or biogas. {1} Use – Fuel or electricity generation. {1}

Question 30

State one advantage and one disadvantage of using commercial anaerobic digesters. {2}

Answer 30

Answer to include any one of the following advantages; {1} • Treats waste and reduces greenhouse gases. • Produces a biogas that can be used as a fuel. • AD can take place at a location local to where waste or energy crop is produced – therefore reduces the need for transportation. Answer to include any one of the following disadvantages; {1} • Requires a steady supply if a consistent feedstock. • Quality of the gases produced will vary, therefore potentially increasing he need for a gas cleansing process to protect the combustion equipment.

Question 31

Outline three advantages of using commercial anaerobic digesters. {3}

Answer 31

Any three from; • AD offers an option to treat waste and produce biogas that can be used as a fuel. • AD diverts the methane that would be released from landfill into the generation of electricity, thereby reducing atmospheric methane levels / greenhouse gas emissions. • AD can take place at a location close to where organic/farm waste is produced therefore reducing the need for transportation/providing local jobs/providing electricity supply/providing waste management options.