Question 19M.3.SL.TZ2.c
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.3.SL.TZ2.c |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Suggest | Question number | c | Adapted from | N/A |
Rice straw waste can be used to produce biogas, but it contains cellulose that is difficult to digest. Bacteria capable of digesting cellulose are found in the cow’s digestive system. Rice straw waste was pre-treated in a batch fermenter with liquid cow manure. A control was kept under the same conditions without the liquid cow manure.
The resultant products of each culture were placed in two separate continuous biogas fermentation tanks with anaerobic bacteria for 30 days under the same conditions. The graph shows the differences in biogas production and amount of methane produced.
[Source: reprinted from Bioresource Technology, 111, Lei Yan et al, Diversity of a mesophilic lignocellulolytic microbial
consortium which is useful for enhancement of biogas production, 49–54, Copyright 2012, with permission from Elsevier]
Suggest one reason for the higher methane content in biogas in pre-treated rice straw waste.
[1]
a. manure contains bacteria that digest cellulose to sugars ✔
b. more substrate/sugars to produce methane ✔
This question concerned the production of biogas from rice straw waste. The candidates had difficulty answering parts (a) and (c).
