With the right ingredients and a few simple tools, you can turn grass clippings, leaves, branches, weeds, and some kitchen waste into sweet smelling humus that contains plant nutrients and retains moisture. Composting speeds up the decay of these organic materials. The amount of time it takes to form humus depends on the materials used to make the compost pile, composting techniques, and the amount of effort you put into the process.

Photo courtesy of Rodale Stock Images.

Freestanding compost piles can be left alone, and over time, they will decompose, depending on moisture and temperature. This method takes little effort, but requires more space than home composting units, which contain the pile, keep animals from digging into it, and allow you to aerate the compost, so it can decay faster.

Most organic material can go into your compost pile: leaves, branches, weeds, grass clippings, vegetable kitchen waste, saw dust, wood chips, egg shells, tea bags, coffee grounds, paper coffee filters, and paper towels.

BUT you shouldn't use:

• Animal feces. They can contain germs that may not be destroyed during decomposition. If the compost is used in vegetable gardens, the germs can make people sick when they eat the vegetables.
• Meat scraps or grease. They attract rats and flies.
• Plastics. They don't break down.
• Coal or charcoal briquette ashes. They are often chemically treated.
• Pesticides and fungicides. They contain toxic materials.

Bacteria, fungi, and other microorganisms break down the organic material inside the pile. Microorganisms that live in temperatures from 50° - 113° F (10° - 45° C) begin the decomposition process. The microorganisms generate heat as they consume and digest the material in the pile. As the pile heats up, other microorganisms that live in temperatures from 113° - 158° F (45° - 70° C) take over the decomposition process.

The bacteria that decompose the pile require moisture and oxygen. If the pile is too dry, or if bacteria use up the available oxygen, the temperature drops and the decomposition process slows down. Turn the pile to add air and keep it moist. If the conditions are just right, you'll have rich compost in as little as three weeks.

Activities: Best Ever Compost (for outdoor composting), and Soda Bottle Bioreactor (for small-scale indoor composting)
Profile: Seattle Tilth Association