Which gases are produced in anaerobic sludge digesters?

Options

A. Methane and `CO_2` only
B. Methane, hydrogen sulphide and `CO_2`
C. Methane, hydrogen sulphide and `O_2`
D. Hydrogen Sulphide and `CO_2`

Explanation

### Step-by-Step Solution:

1. **Understanding Anaerobic Conditions**:
- Anaerobic means the process occurs in the absence of oxygen. In anaerobic sludge digesters, microorganisms break down organic matter without oxygen.

2. **Identifying the Process**:
- In anaerobic digestion, bacteria decompose organic material, leading to the production of various gases as byproducts.

3. **Recognizing the Gases Produced**:
- The primary gases produced during anaerobic digestion include:
- **Methane (CH₄)**: A significant product of anaerobic digestion, methane is a potent greenhouse gas but can be harnessed as a renewable energy source.
- **Carbon Dioxide (CO₂)**: Another major byproduct of anaerobic digestion, carbon dioxide is released alongside methane.
- **Hydrogen Sulfide (H₂S)**: This gas is produced in smaller amounts and is known for its characteristic rotten egg smell. It can be toxic in high concentrations.

4. **Evaluating the Options**:
- Given the options:
- A: Methane, Carbon Dioxide only
- B: Methane, Hydrogen Sulfide, and Carbon Dioxide
- C: Methane, Hydrogen Sulfide, and Oxygen
- D: Hydrogen Sulfide and Carbon Dioxide only
- The correct answer must include methane, carbon dioxide, and hydrogen sulfide while excluding oxygen.

5. **Selecting the Correct Answer**:
- Option B (Methane, Hydrogen Sulfide, and Carbon Dioxide) is the correct choice because it accurately reflects the gases produced in anaerobic sludge digesters.

### Final Answer:
The gases produced in anaerobic sludge digesters are **Methane, Hydrogen Sulfide, and Carbon Dioxide**. The correct option is **B**.