Biogas is the mixture of gases produced by the microbial activity. The type of the gas produced depends upon

Options

A. type of microbes
B. type of organic substrate/waste
C. size of digester
D. 1 & 2 both

Answer

**Step-by-Step Solution:**

1. **Understanding Biogas Production**: Biogas is produced through the microbial activity during the anaerobic digestion of organic matter. This process involves the breakdown of organic materials by microorganisms in the absence of oxygen.

2. **Identifying Key Components**: The primary gas produced in biogas is methane (CH4), along with other gases such as carbon dioxide (CO2) and hydrogen (H2). The production of these gases is influenced by the types of microorganisms involved and the organic materials being digested.

3. **Role of Microorganisms**: Specific types of bacteria, known as methanogens, are responsible for producing methane. These bacteria thrive in anaerobic conditions and are crucial for the fermentation process that leads to biogas formation.

4. **Influence of Organic Substrate**: The type of organic material (substrate) being digested also plays a significant role in determining the composition of the biogas. For example, substrates rich in cellulose can lead to higher methane production.

5. **Evaluating the Options**: The question provides several options regarding what influences the type of gas produced in biogas:
- Types of microbes
- Types of organic substrate or waste
- Size of digester
- Both types of microbes and organic substrate

6. **Analyzing Each Option**:
- The **types of microbes** (e.g., methanogens) directly affect the gas composition.
- The **types of organic substrate** also influence the amount and type of gas produced.
- The **size of the digester** does not significantly affect the type of gas produced, although it may impact the efficiency of the process.

7. **Conclusion**: Since both the types of microbes and the types of organic substrates are critical in determining the type of gas produced, the correct answer is that both factors (1 and 2) are important.

**Final Answer**: The type of gas produced in biogas depends on both the types of microbes and the types of organic substrate or waste. Therefore, the correct answer is option 4: both 1 and 2.

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