Question 19N.3.SL.TZ0.8
| Date | November 2019 | Marks available | [Maximum mark: 4] | Reference code | 19N.3.SL.TZ0.8 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Distinguish, Identify, Suggest | Question number | 8 | Adapted from | N/A |
The diagram below represents a small-scale biogas fermenter.
[Source: © Science in Society. http://www.i-sis.org.uk/BiogasChina.php]
Suggest one material that could be loaded into the biogas fermenter from which biogas can be produced.
[1]
blackwater
OR
brownwater/sewage
OR
feces
OR
organic solid waste
OR
paper pulp
OR
other biodegradable material ✔
Do not accept methane and CO2.
Identify the ideal temperature and oxygen conditions inside the fermenter for efficient biogas production.
Temperature:
Oxygen:
[1]
temperature warm and oxygen concentration low / anaerobic ✔
Accept above room temperature / 20 to 70°C for warm, depending on bacteria used.
Both required.
Distinguish between batch and continuous culture fermentation.
[2]
a. in batch culture product is withdrawn at the end of the «organisms» growth phases whereas in continuous culture product is withdrawn while the organism is growing / OWTTE ✔
b. in batch culture all of the growth medium/nutrients are added at the beginning whereas in continuous culture, growth medium/nutrients are added at a constant rate / OWTTE ✔
c. batch culture is carried out in large scale fermenters whereas continuous culture could be in small scale ✔
d. continuous can run for a longer time than batch ✔
