The residue left after methane production from cattle dung is

Options

A. burnt
B. burried in land fills
C. used as manure
D. used in civil construction

Explanation

To answer the question about the residue left after methane production from cattle dung, we can follow these steps:

### Step 1: Understand the Process of Methane Production
Methane is produced through anaerobic digestion of organic materials, such as cattle dung, in biogas plants. This process involves microorganisms breaking down the organic matter in the absence of oxygen.

**Hint:** Think about the environment in which methane is produced and the materials involved.

### Step 2: Identify the By-products of Methane Production
During the anaerobic digestion process, not only is methane produced, but there is also a residue left behind after the biogas (which is rich in methane) is collected. This residue is the undigested organic material.

**Hint:** Consider what happens to the organic matter that is not converted into gas.

### Step 3: Analyze the Composition of the Residue
The residue from the methane production process contains nutrients, cellulose, and lignin. These components make it rich in organic matter and beneficial for soil health.

**Hint:** Think about what nutrients are typically found in organic fertilizers.

### Step 4: Determine the Use of the Residue
Due to its nutrient-rich composition, the residue is often used as manure. It serves as an excellent organic fertilizer for agricultural purposes, enriching the soil and promoting plant growth.

**Hint:** Consider how farmers might utilize waste products to improve crop yields.

### Step 5: Conclusion
The residue left after methane production from cattle dung is used as manure, making it an ideal organic fertilizer for enhancing soil fertility.

**Final Answer:** The residue left after methane production from cattle dung is used as manure.