The question asks why biomedical waste requires special handling compared to general municipal waste. Let's analyze the given options to identify the correct reason:

1. Option 1: It is more likely to be recycled than other types of waste.

   This option is incorrect. Biomedical waste is typically not suited for recycling due to its potential health hazards and must be disposed of in a manner that ensures no risk to human health or the environment.

2. Option 2: It has higher chemical content and is always toxic.

   While some biomedical waste may contain chemicals, it is not accurate to say that all biomedical waste is toxic or that it constitutes a higher chemical content universally. Thus, this option is not the primary reason for special handling.

3. Option 3 (Correct): It may contain infectious agents that pose health risks.

   This is the correct option. Biomedical waste can include sharps, human and animal tissues, blood, and other body fluids that may contain pathogens. These infectious materials can pose serious health risks to people who come into contact with them, necessitating special handling protocols to prevent disease transmission.

4. Option 4: It is always radioactive and requires heavy shielding.

   This option is incorrect. Although some biomedical waste in hospitals may be radioactive (e.g., from certain medical or research activities involving radioactive materials), the statement that biomedical waste is always radioactive is inaccurate and misleading.

Conclusion: Biomedical waste requires special handling because it may contain infectious agents that pose health risks. Proper segregation, treatment, and disposal are crucial to prevent the spread of infections and protect public health and environmental safety.