Food Scrap Composting

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Properly composted food scraps can turn into an excellent fertilizer. However, composting food scraps in a regular backyard compost bin can be tricky. If done incorrectly, backyard composting of food scraps can attract some potential pests (ex. rats, mice, raccoons and opossums). Fortunately, there are three simple ways to compost your food scraps without fear of attracting potential pests.


Please keep in mind that all three of these methods are ONLY for composting fruit and vegetable trimmings, bread, rice, pasta, tea bags, coffee grounds, coffee filters and other such materials. Do NOT attempt to compost meat, fish, dairy products, pet waste or greasy food through these methods. These items can attract pests and cause problems during composting.

Worm Bin

Option #1:
Worm Composting

Vermicomposting, a.k.a., worm composting, is the practice of using worms to do your composting. The worms feed on your fruit and vegetable trimmings and decompose them for you. The goal of vermicomposting is to create the ideal environment for worms to thrive so they can efficiently decompose the material you feed them. Worm composting is simple. You need a box, bedding, fruit and vegetable trimmings, and worms.  More detailed information about worm composting.

In-Ground Composting
Option #2:
In-Ground Composting

A very simple way to compost your food scraps is just to bury them at least 8 inches deep in your garden. Garden soil provides a natural barrier that keeps out flies and other pests, and holds in moisture and odors. If you have dogs that like to dig in your garden, this approach may not be the best for you.

Food scraps can be buried in empty areas of vegetable and flower gardens, or in holes outside the drip line (below the ends of branches) of trees and shrubs. Use a shovel or post hole digger to dig a hole or trench about 1 foot deep. Add 2 to 3 inches of food scraps to the hole. Chop and mix scraps into soil, then cover the food scraps with at least 8 inches of soil to keep pests out.

Check occasionally for signs of digging by rodents, dogs or other pests. If you see signs of digging, it may be better to switch to a digester or worm bin.

Food scraps may take from 1 to 6 months to decompose depending on the season, moisture, soil and the type of food scraps that are buried. Seeds and small seedlings may be planted on top of buried food scraps immediately. Large transplants should not be planted until the food has decomposed. Do not bury more food scraps in the same place until the first scraps have been fully composted.

Option #3:
Composting with a Food Digester

Making a Food Digester
One of the simplest ways to compost food waste is in a food digester. You can buy one pre-made, or you can make your own using a galvanized metal garbage can (a 32 gallon can works well). The can should have a tight-fitting lid. Drill or punch about 20 drain holes, 1/4 or 3/8 inch diameter, in the bottom of the can. Drill 20 more holes in the sides of the can, but only in the lower third, which will be covered by soil.

Food Digester

It is very important to make sure that the lid fits snugly on the can to keep raccoons and other pests out. If the lid does not fit tightly you can make a lid out of a piece of ply-wood, with a handle on the top and some wood blocks underneath to fit the lip of the can and help hold the lid on. If needed, a bungee cord or rope can be attached to the lid handle and the can handles to secure the lid.

Dig a hole at least 15 inches deep in a well-drained area of your yard and set the can into the hole. The can should be 1/3 to 1/2 buried in the soil—none of the holes you drilled should be visible above the soil. Once the hole is deep enough, push the soil back in around the sides. Your new food digester is ready to use! You do not need to add worms to your digester—worms will find their way into the digester through the holes and will help break down the food scraps.

Composting With Your Digester
Now that your food digester is ready, you can start adding food scraps. You can collect your food scraps in a container in the kitchen, and place the food scraps in your food digester once or twice a week. Be sure the digester lid is on tight after adding the food scraps.

Harvesting the Compost From Your Digester
Depending on your household’s food habits, the digester will fill in 4-12 months. Once the digester is full, the compost can be harvested.

Harvesting the compost is simple. Shovel the upper foot or so of un-composed food off to oneside and shovel the dark, soil-like compost out of the bottom. While harvesting compost from your digester, watch out for the jagged metal around drainage and air holes. If the finished compost is wet and smelly, mix it with some soil, lay it in the sun and wait a week for it to turn drier and sweet smelling. Place the un-composted material back in the digester for further composting. You can also bury the top layer in a trench in the garden, making more room for food scraps in the can.

The simplest way to get completely finished compost without strong odors is to install two digesters. When one digester gets full, just start using the second digester. Usually, by the time the second digester is full, the material in the first digester has finished composting (6-12 months) and is ready to harvest and use.

Using Compost From Your Digester
Before using the compost from your digester, be sure to dry it in the sun for a few days. Drying out the material will work to cure the compost. It will also make the compost easier to spread.

Compost can be used as mulch on established plants, as a soil amendment at planting time, and in potting mixes. Food scrap compost contains more nutrients than yard waste compost, and should be used more sparingly. It can be applied as a one-inch mulch around plants or up to two inches can be dug into garden soil. For a potting mix, add up to 20% food scrap compost to a commercial or homemade potting mix.

Food Digester Trouble Shooting
The best way to keep odors and fruit flies at a minimum is to make sure the digester lid always fits tightly. If flies and odor are still troublesome, stir in leaves or coarse sawdust to keep the food scraps aerobic. When adding more food scraps, you can also cover fresh food scraps with leaves, coarse sawdust, straw or shredded newspaper to exclude fruit flies. If you prefer to use grass clippings as a covering material, first leave them in the sun to dry out and turn brown. Keep in mind that adding dry material each time food scraps are added will make your digester fill up faster. Another way to cut down on flies in your food digester is to hang strips of fly paper on the inside of the digester lid. Once a healthy worm population is established in the digester, they will help reduce odors by aerating the food scraps. The inside of the digester may have a slightly unpleasant smell and some fruit flies—the goal is to make sure that the outside of the digester does not smell or have flies buzzing around.

It’s important to keep the lid on your digester closed to keep pests out. Place a rock on the lid or tie the lid handle to the handles on the sides of the garbage can to hold the lid on. Also, be sure to keep meat, fish, dairy and greasy food scraps out of your digester. They will smell bad and attract animals, so it is better to put them in the garbage.

Sources:

More Information
See www.davisrecycling.org for more information about composting and City taught composting classes.

Additional information about composting can be found on the California Department of Resources Recycling and Recovery website www.calrecycle.ca.gov/Organics/HomeCompost/