How to Build and Use a Trash Can Composter

1. Select a Trash Can

   Choose a 32-gallon or larger plastic or metal trash can with a tight-fitting lid. If rodents or other pests are a problem in your area, a metal can is recommended.

2. Drill the Holes

   Using a drill with a 2- or 3-inch hole saw, drill holes all the way around the trash can (lid, bottom, and sides) roughly 6 to 12 inches apart. These holes will provide the airflow and oxygen necessary to enhance the composting process.

3. Attach the Screening

   Cut pieces of metal window screening large enough to cover each hole. Cover each hole on the inside of the can with a patch of window screening, securing it with epoxy or silicone caulk.

4. Position Your Trash Can Composter

   Put your trash can composter in a convenient place. If possible, raise it up on a couple of bricks to allow air circulation under the can.

5. Add Compostable Material

   Begin adding plant-based organic materials to the composter. A trash can composter can accept anything you would put in a standard compost pile, including fruit and vegetable peels and cores, leftover cooked veggies (as long as they don't have salt or butter on them), produce that's past its prime, coffee grounds, tea leaves and tea bags, shredded newspaper, and weeds, leaves, spent flowers, and other garden trimmings.

   If you have too many "green materials," such as fruit and veggie peels, weeds, and grass clippings, the pile will stay too wet and start to smell. But if you have too many "brown materials," such as leaves, twigs, shredded paper, and coffee grounds, the pile will fail to generate the necessary heat and decompose very slowly. Try for a ratio of at least 4:1 of browns to greens.

   Tip

   To speed decomposition, add a handful of nitrogen fertilizer or a small amount of commercial compost starter. Compost starter includes a mixture of nitrogen and microorganisms that promote decomposition. You also can add a shovelful of garden soil, which contains microorganisms that help break down the compost.

6. Monitor and Turn the Pile

   In general, compost should feel like a wrung-out sponge—slightly damp but not sopping. Anything that's wetter than that will start to smell because it has become anaerobic, meaning oxygen is not reaching parts of the pile. On the flip side, a pile that is too dry generally will not emit any warmth. Monitor the moisture level throughout the decomposition process, and adjust your ratio of greens to browns accordingly.

   In addition to moisture, you'll also need to keep your compost aerated to provide oxygen. In a traditional pile, this is done by digging into the pile and turning the contents every week or two. You can aerate your trash can composter by simply laying it on its side and rolling it a few times. Do this once or twice a week until the compost is ready to use.

7. Use the Compost

   Your compost is ready to use when it has reached a uniform, crumbly, dark brown appearance and no longer emits any warmth. This indicates the materials have fully broken down. You can use it in many ways, including applying it as a surface dressing to mulch around shrubs, trees, and other plants or as a soil amendment to improve the texture and fertility of soil before planting.

How Composting Works

Compost is essentially just organic (carbon-based) material that has decomposed—broken down into simpler components under the action of helpful microorganisms, including bacteria and fungi. Any organic material will eventually break down on its own, but a compost bin helps to speed up the process by deliberately combining the necessary ingredients: organic material, moisture, oxygen, and bacteria. As organic material breaks down into usable compost, the nutrients are unlocked into a form plants can use.

Composting Without Air

The traditional composting method requires oxygen. It's known as aerobic composting. But it's also possible to compost anaerobically (without oxygen). This is accomplished by confining organic material and moisture in an environment that lacks airflow. The process uses a different group of microorganisms, and it takes considerably longer than traditional composting. But in the end, it also produces nutritious compost.

Trash cans with lids are perfect containers for this kind of composting. Instead of drilling lots of air holes in the container, drill only a few drainage holes in the bottom. Then, keep the container tightly sealed except when you are adding material. Such compost does generate odor, but this generally is not a problem because you'll be keeping the can sealed.

Composting Tips

Compost loses volume as the organic material breaks down. You can continue to add materials as the level in the trash can drops. But eventually, you should stop adding materials to allow the contents to fully convert into compost. Some gardeners keep several compost bins in various stages of decomposition, so they can harvest compost from one bin while others are in earlier stages of decomposition.

Although weeds can be composted, their seeds might remain viable unless the compost bin generates enough heat to kill them. Many home compost bins don't develop the necessary heat. Thus, the weed seeds can spread and grow in your garden. For this reason, some gardeners avoid putting weeds into the compost bin.

Furthermore, don't compost plant material that has clear signs of disease, such as fungal leaf spots. Sometimes these pathogens will survive the composting process and can be spread around the garden as you use the compost.

Finally, sticks and twigs can be composted, though they take a while to break down. Some gardeners keep a dedicated compost bin for these coarser materials, mixing them with finer-textured "green" materials and allowing a full year for them to break down into compost. It helps to chop up sticks into small bits before adding them to the bin.