Question

Read the following statements about aerobic composting of organic fraction of municipal solid waste:
I. The majority of the odour problem in an aerobic composting process is due to the development of anaerobic conditions within the compost pile.
II. All organic carbon present in the waste will completely biodegrade in 14 days.
III. At high C/N ratio, ammonia would be released and biological activity may also be impeded.
IV. Optimum moisture content for aerobic composting process would be 50–60%. Lower moisture would slow down the biological process. Excessive moisture will make it difficult to maintain aerobic conditions.
The correct choice(s) is/are:

• A. I and IV are correct
• B. II and III are incorrect
• C. I is correct; IV is incorrect
• D. II is correct; IV is incorrect

Hint:

- Ideal composting requires C/N ratio of 25–30 and moisture 50–60%.
- Too high moisture → anaerobic pockets and odour.
- Too low nitrogen (high C/N) → slows decomposition.

Answer 1

The Correct Option is A, B

Step 1: Evaluate Statement I.
- Odour problems in composting are caused by anaerobic pockets that develop inside the pile when oxygen is insufficient. - This produces methane, hydrogen sulphide, and volatile fatty acids → foul smell. - Hence, Statement I is correct.
Step 2: Evaluate Statement II.
- Complete biodegradation of all organic carbon within 14 days is not possible. - Composting usually takes several weeks to months depending on conditions. - Hence, Statement II is incorrect.
Step 3: Evaluate Statement III.
- At a high C/N ratio, there is excess carbon but insufficient nitrogen. - This slows down microbial growth, but does not lead to ammonia release. - Ammonia release occurs when C/N ratio is too low (excess nitrogen). - Hence, Statement III is incorrect.
Step 4: Evaluate Statement IV.
- The optimum moisture content for aerobic composting = 50–60%. - Too little moisture → microbes become inactive. - Too much moisture → oxygen diffusion reduces → anaerobic conditions. - Hence, Statement IV is correct.
Step 5: Conclude.
Correct statements = I and IV. Final Answer: \[ \boxed{\text{(A) I and IV are correct}} \]