The biology and chemistry of composting is pretty complicated, says master composter Linda Mizes, but you don't have to understand it completely to successfully create a compost pile.
Mizes, a master gardener in Contra Costa, Calif., shares these tips.
A compost bin or pile needs four things:
The food consists of an equal mix of green and brown material, which feed the bacteria, fungi and other creatures. The BFFs, as Mizes call them, help decompose the materials and convert it to humus, or soil.
Green materials are high in nitrogen, and can include grass, kitchen scraps, manure and coffee grounds. Mizes also puts her weeds into her compost bins, as long as the weeds have not yet gone to seed.
Brown materials are high in carbon, and can include leaves, twigs and paper.
Egg shells are neither green nor brown, but they can add calcium to your mix and are okay to add to your pile.
Your compost materials should have the consistency of a damp sponge. Add water as needed.
Air also is essential for the decomposition to take place. Stirring your compost will help aerate it.
There are two kinds of composting — hot and cold — but a certain amount of warmth is required for both. Put your piles or bins in a sunny spot. Most bins are black to help absorb and maintain the heat in your pile.
Manage your pile
Chop your materials into smaller pieces to increase the surface area and facilitate decomposition. Many plants have a protective cover that resists decay, so cutting them into bits or shredding can break down that cover.
To minimize water and heat loss, pile your materials in a heap, or use a composting bin.
Be sure to place it near a water source and in an area that will be convenient for you to access.
Tend your compost by turning the materials to add air, distribute the moisture and to enhance decomposition.
Monitor the pile for moisture levels and check for surprises, Mizes says, such as mammals moving into the bins to build nests.
You can harvest your compost when about half of the materials have turned to humus. Return the materials not fully decomposed to the pile.
Running your finished compost through a sieve or screen can remove pieces that aren't quite fully composted.
The best way to do this is to pull all of the material out and sift it. Keep the humus and use the rest to start a new batch.
If your bin has a strong odor, you may have too much water or too much nitrogen. Try adding in more browns.
To stop rats or other creatures from burrowing into the bin, use a piece of chicken wire on the bottom.
Using a piece of plastic on top of your materials can help keep the moisture inside.