Biomass

Question 1

Rank the following in terms of CO2 per GJ released when oxidised:

• Coal
• Oil
• Wood
• Natural Gas

Answer 1

1. Natural Gas (50kg)
2. Oil (70kg)
3. Wood (77kg)
4. Coal (90kg)

Question 2

What is gasification?

Answer 2

Reacting steam and air/oxygen with a solid fuel to produce a gaseous fuel. The resultant fuel is cleaner but has a lower calorific value.

Question 3

What is pyrolysis?

Answer 3

Heat treating the biomass to drive off volatile components, leaving an energy dense char.

Question 4

What is fuel synthesis?

Answer 4

Gasifier producing CO2 and H2 can provide the feed stock for synthesis fuels and can produce alcohols and hydrocarbons.

Question 5

What is anaerobic digestion?

Answer 5

Similar to pyrolysis, but the process is completed at low temperatures using bacteria.

Question 6

What is biogas?

Answer 6

Anaerobic digestion of sewage and animal dung by micro-organisms.

Question 7

What is landfill gas?

Answer 7

Capturing the gas and run off from domsestic waste. This must be done in an impermeable (clay) pit to prevent leakage into the environment.

Question 8

What is fermentation?

Answer 8

Anaerobic biological process of converting sugars into alcohol using micro-organisms (yeast). The resulting alcohol can be mixed with gasoline to make a fuel that can be used in ICEs.

Question 9

What are the disadvantages of using biomass as an energy source?

Answer 9

• Short carbon cycle, no carbon is actually removed from the atmosphere
• Still causes deforestation
• Low calorific value
• Impact of fertilisers should be accounted for
• Could be competing with land for growing food

Question 10

What are the energy densities of dry biomass and alcohols/biodiesels?

Answer 10

15MJ and 38MJ per kg respectively.