By plastic

Dirt. When you put vegetable scraps into a container with holes in it for air, dead leaves, some water, and dirt, (worms are extremely helpful for composting) the scraps break down into moist, airy dirt that is good for gardens or house plants. If you mean to keep composting for a long time, you can buy a composting barrel, that is a barrel on a stand you can spin around easily.

Composting is the action of breaking down vegetable waste into useable soil, so you get soil from composting, you don't use soil for composting.

Because worm composting is healthier to the environment and healthier to the earth. :)

Composting is the thing of recycling of organic waste. This is the sentence containing composting word.