Compost tumblers often come with advertisements of speedier compost production--from kitchen waste to "black gold" in 14 days. Reports on the veracity of that claim vary; however, some advantages are guaranteed. A compost tumbler is convenient if you have limited space to compost in. It keeps pests out and odor in. And it makes the all-important job of mixing and aerating the compost a snap.
About a quarter of your tumbler's contents should be organic waste high in nitrogen and moisture, known commonly as "green stuff." This means almost all of your kitchen waste: vegetable scraps, egg shells, coffee grounds, tea leaves and tea bags. It also includes any garden, yard, or farm waste that's still wet and green: hay, grass clippings, weeds and pruned stems.
Give your tumbler a turn or two after adding a lot of grass clippings. Otherwise, these may form a solid matted layer that suffocates the oxygen-loving microorganisms that make your compost.
About three quarters of what you put in your tumbler should be dry, carbon-rich "brown stuff". This includes dry leaves, sawdust, straw, wood chips, shredded newspaper and cardboard.
Unpleasant odors are a sign you need to add more brown stuff. You can also add more to absorb excess water if your compost is too wet.
Check your compost periodically; it should remain about as moist as a wrung-out sponge. Add a small amount of water if it's too dry. It's likely you won't have to very often. The water in the green stuff you add will usually suffice, especially considering that a compost tumbler tends to retain moisture well.
Materials in a compost tumbler are isolated from the microorganism-rich soil. Toss in a handful of dirt to help jump-start the process.
Optionally, you can give the composting process a boost by adding ingredients high in nitrogen, microorganisms or both. You can buy commercial products (for examples, click the Amazon.com link in the Resources section), or you can add such materials as seaweed, aged manure, blood meal, alfalfa meal or cottonseed meal.
Oxygen is of course an essential ingredient in aerobic composting. Ease of aeration is the most distinctive advantage of a compost tumbler. Every time you turn the crank or roll the barrel, you add air.
Human and pet manure carry diseases, as do infected plants. Pernicious weeds may resprout. Do not add these things unless you know for sure that your compost will reach and maintain the very high temperatures required to kill pathogens and weed seeds (140 to 160 degrees Fahrenheit).
Most compost experts recommend against meat and fish scraps, fatty food wastes, milk products and bones. However, the biggest reasons, that they attract pests and smell bad, don't apply in container compost systems such as tumblers. These meat and dairy items do bring a risk of "overheating" your compost, though, so if you choose to add them, monitor your compost's temperature and add brown stuff to bring it down if necessary.
Do not add pressure-treated lumber, colored papers, or coal ash. These contain toxins that could hurt your garden.
Lastly, leave out any inorganic materials such as glass, rocks, and metals. These will not break down.