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City of San Diego Guide to Backyard Composting

What is Composting and Why Do It?

Composting is nature's way of recycling. It is the controlled natural decomposition of organic material, such as leaves, grass clippings, prunings, and fruit and vegetable scraps. Microorganisms break down these materials into compost, or humus, the nutrient rich soil product that results from proper composting.

Getting Started

Composting can be practiced almost your backyard, at work or school, even if you live in an apartment! All you need to get started composting is a little bit of space, a bin, and a basic understanding of the composting process.


Your compost pile will need an area about 3 foot square. Vermicomposting uses less space, and is better suited for apartment residents and small yards - it's easy to build your own worm bin, too.

The pile should be located in a partially shady spot, so that the sun doesn’t dry out your compost too quickly. You may want to plan for extra space around your pile to make turning and harvesting your compost easier.

Compost Bins

A compost bin will help to keep your compost pile neat and tidy, deter rodents from digging in your pile, and help your pile retain heat and moisture during composting. Compost bins can either be homemade or purchased from a bin manufacturer. Ideally, your compost bin should be at least 3 feet wide x 3 feet deep x 3 feet tall. Even if your bin is not this large, it will work just fine if managed properly. Take the time to consider your options and the style of composting that is most convenient for you.

Homemade bins

Homemade bins can be easily constructed out of wood, wire mesh, scrap pallets, or other materials commonly found in your home. For instructions, check out Build Your Own Backyard Bin.

Manufactured Bins

Manufactured bins include turning units, cone-shaped bins, and bins with stacking tiers. These bins can be purchased at nurseries and garden centers, or mail-ordered directly from the manufacturer. To see examples of the different types of composting bins available, visit one of the Composting Demonstration Gardens at the San Diego Zoo, the Water Conservation Garden, or the Environmental Services Department Ridgehaven building. Contact Solana Cener for directions, or register for an upcoming composting workshop in your area.

Composting Basics

Making compost is a lot like cooking a meal. You take some basic ingredients, add water, mix well and let it “cook” over a given period of time. In as little as 12 weeks, you can have finished compost ready to use in your garden.


Four basic ingredients are required for composting: GREENS, BROWNS, WATER, & AIR. Mixing the proper amounts of these ingredients together will provide the composting organisms (microbes and insects) with enough nitrogen, carbon, moisture and oxygen to break down the material efficiently. 

How to tell when your compost is ready

Your compost is finished when the original materials have been transformed into a dark brown, crumbly soil product with a pleasant, earthy aroma. None of the materials originally placed in the bin should be recognizable. There may be a few chunks of woody material left, as these are generally slower to break down. These can be screened out and used as mulch or placed in the next batch of compost to continue decomposing.

Screening your compost of any large, un-decomposed materials before placing it in your garden is a good idea. Screening keeps valuable nitrogen and oxygen from being robbed from the soil as the un-decomposed materials continue to break down. Screened compost is also much easier to use as an amendment in potting soil and top dressings.

You can build a simple screen for your compost by nailing a 3-foot square piece of 1/2” wire mesh to a wooden frame. This frame can be set over a wheelbarrow, to catch the screened compost as it falls through the mesh.

Using Your Finished Compost

Compost can be incorporated into your garden soil, spread like mulch or as a top dressing on your planters and lawn, or used as a potting mix or seed starter.

Soil incorporation is the most common use for compost. In San Diego, where the soil is either sandy or clay, mixing compost in with the soil helps to improve its texture, and increase its nutrient level and water holding capacity. Spread 2 to 4-inches of compost over the soil and turn it in with a shovel to a depth of about 6 inches.

Top dress your planters by spreading compost to a depth of 3-inches around the base of plants and shrubs, much like you would spread a mulch. For lawns, hand cast screened compost over the surface of the lawn, to a depth of 1/2 inch. 

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