Mother Nature is the ultimate recycler: She returns living organisms back to the earth after they die. As the organisms decompose, the nutrients they contain are broken down and returned to the soil, where they are available to be used by future plants and animals.

Essentially, decomposition is what happens when an incredible array of organisms, both large and small, eat nature's "leftovers." Decomposers include worms and beetles as well as beneficial fungi and bacteria.

Get students thinking about nature's recycling by asking questions, such as "Where do all the leaves go when they fall in autumn?" and "What would happen if those leaves didn't decompose?" Take advantage of the abundant learning opportunities by setting up your own composting experiments. You can construct basic compost piles outside in your garden or create an indoor worm composting bin.

Outdoor Bins
Although all organic materials will eventually break down, the most efficient compost piles include a variety of organic matter, which can be loosely classified as "browns" or "greens." Greens are rich in nitrogen and include grass clippings and vegetable scraps. Browns are rich in carbon and include fallen leaves and straw.

By alternating greens and browns, keeping the pile moist but not soggy, and turning the pile to keep it aerated, you'll attract the organisms responsible for efficient, odor-free decomposition. (A wet, compacted pile will still decompose, but the process will result in unpleasant odors due to the types of organisms that flourish in that environment!)

A 3-foot by 3-foot pile is a good size. Larger than that and the materials will take longer to decompose; smaller than that and the pile may not heat up enough to completely decompose.

Indoor Worm Bins
Most kids are fascinated by worms, unless they've been taught otherwise. You can replace or supplement your outdoor composting efforts by starting an indoor worm composting bin. Although you can build your own simple worm bin with a plastic container, purchased bins will have extra features, such as a spigot to drain off excess moisture, that make them a bit easier to maintain.

In a nutshell, to create a worm bin you place special worms* in a plastic container with a bed of moist newspaper. You feed them vegetable scraps, which they devour and, in the process, turn into worm castings — a great organic fertilizer. Worm castings are a rich, dark brown, have a pleasant earthy smell, and somewhat resemble coffee grounds. They are high in nutrients and can be added to houseplant soil mixes, incorporated into garden beds, or spread on the top of soil as a mulch, so that the nutrients seep in during watering.

*Unfortunately, the earthworms kids collect from the outdoor soil won't survive in a worm bin. For indoor bins, the worms of choice are red wigglers. These slender worms eat just about everything — fruit and vegetable peels, pasta, rice, bread, coffee grounds, tea bags, and trimmings from the garden. Just as in a regular compost pile, however, don't add dairy products, oils, or meats.

For more information about composting visit these Kidsgardening.com resources:

The Rottin' Truth
Build a Worm Bin
Composting Worm Care
Leftover Lessons
Digging Deeper with Compost
Exploring Decomposition