Concept:
Organic waste can be converted into nutrient-rich compost through biological decomposition methods.
Step 1:
Composting is the process of converting biodegradable waste into useful manure.
Step 2:
Vermicomposting uses earthworms to decompose kitchen waste and organic matter into compost.
Step 3:
• Wormicombustion is not a scientific waste management term.
• Garb-condensation is incorrect terminology.
• Kitchen-garden recycling is a general phrase, not the correct process name.
Step 4:
Therefore, compost preparation using earthworms is called Vermicomposting.
\[
\boxed{\text{(3) Vermicomposting}}
\]