Compost pile with plant scraps and dry leaves in a yard

Home composting: what to add and what to avoid

Balance between green and dry materials

Home composting works when a reasonable ratio between green scraps and dry materials is maintained, and when the pile is turned fairly often. In this article we review which kitchen and garden waste can be added without problems and which is best avoided so as not to attract animals or cause bad odors. We also explain how to read the process signals: temperature, moisture, and texture. With patience and observation, the compost bin becomes a steady source of fertilizer for the garden beds and a concrete way to close the organic matter cycle at home.

The ratio that usually works in a backyard compost bin is roughly one part green material to every two or three parts dry material. Greens provide nitrogen and moisture: fruit peels, vegetable scraps, coffee grounds, tea bags without the string, freshly cut grass. Browns provide carbon and air: fallen leaves, cardboard without glossy ink, paper towel rolls, small shredded branches, untreated sawdust. If the mix leans too far toward greens, the pile becomes compacted, gives off a sour smell, and attracts flies. If it leans too far toward browns, the process slows down and you barely feel any heat when you put your hand in.

What should be left out is shorter than people think. Meat scraps, bones, fish, dairy, and fats do not go in: they break down poorly and attract dogs, cats, and rodents. Nor do pet waste, diapers, cigarette butts, or diseased plants or plants with mature seeds, because they often survive the process. Citrus in large amounts, onion and garlic peels in excess, or bread can be added in small proportions, but not as the base of the pile.

To read the process there are three simple signs. Temperature: an active pile feels warm in the center when you insert a stick. Moisture: it should be like a wrung-out sponge, neither dripping nor dry. Texture: if when you turn it material still recognizable appears, the pile needs more time and one more turn. Aerating every week or every ten days, especially in summer, prevents the center from compacting and odors from appearing. In winter the pace slows down and there is no need to force it.

When the compost is ready it looks dark, smells like forest soil, and what was added can no longer be distinguished. It is used as an amendment in the beds, mixed with the soil or as a fine mulch. It is not a concentrated fertilizer nor does it replace other soil tasks, but it closes the cycle of organic matter at home and returns to the garden part of what came out of it.

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Home composting: what to add and what not to add

A backyard compost bin doesn't fail for lack of technology: it fails when you fill it without paying attention. The ratio of green scraps to dry material, aeration, and moisture are the three things you need to manage. In this article we've gathered what you can safely add and what's best left out so you don't attract animals or create odors.

Compost pile with plant scraps and dry leaves in a backyard

Green kitchen scraps

Fruit and vegetable peels, coffee grounds, tea bags without the string, and wilted leaf scraps go in without a problem. It's best to cut them into small pieces so they break down evenly and don't clump together in one spot in the pile.

Dry garden material

Dry leaves, already-yellow grass clippings, shredded branches, and unprinted cardboard are the counterweight to the greens. If the pile stays too wet and compact, that's a sign this part is missing. Aerating with a fork every so often helps keep the process from stalling.

What's best to avoid

Meat, fish, dairy scraps, bones, and oils do not belong: they attract rodents and create a strong odor. Nor should you add pet waste or diseased plants, because they can transfer pathogens to the compost you later use in the garden beds.

Read the signs of the process

If the pile is warm inside and smells like damp earth, it is doing well. If it gives off a sour or ammonia smell, there is too much moisture and not enough air. If it is cold and dry, you need to water it a little and add more greens. The final texture should resemble loose leaf mold.

Patience before haste

Compost matures at its own pace, depending on the climate and the size of the pieces. There are no shortcuts that work: turning, observing, and adjusting is what keeps the process going. When it is ready, it is worked into the soil of the garden beds and closes the cycle of organic matter at home.

Home composting: what should and should not be added

Before adding the first bucket of scraps to the compost bin, it is worth clarifying a few things. Not everything that comes out of the kitchen or everything pruned in the garden ends up being good material, and the difference between healthy compost and compost that attracts flies or gives off a sour smell usually lies in those details.

Which kitchen scraps can I throw in without a problem?

Fruit and vegetable peels, coffee grounds with their paper filter, tea bags, crushed eggshells, and green leaf scraps from the garden are the basis of the moist or "green" material. Soft pruning trimmings and weeds that have not yet gone to seed also work. The practical rule is simple: if it is plant-based and breaks down quickly, it goes in. Cooked leftovers, on the other hand, are better in small amounts and buried well in the center of the pile, because they attract animals more easily.

Which materials should be left out?

Meat, bones, dairy, fish, and fats are out: they generate strong odors and attract dogs, rodents, and flies. It is also not advisable to add pet or carnivore feces, diapers, cigarette butts, "biodegradable" plastics without certainty of their origin, or diseased plants or plants with mature seeds, because they can spread the problem to the garden beds. Glass, metal, and residues treated with herbicides are excluded for obvious reasons. When in doubt, it is better not to add it and compost it by another method or discard it.

How do I know if the ratio is right?

The most widely used reference is one part green material to two or three parts dry material: fallen leaves, dry grass, unprinted cardboard, untreated sawdust, wood shavings. If the pile stays very wet and compact, it lacks dry material; if it looks too straw-like and does not progress, it lacks green material. The ideal texture is that of a wrung-out sponge: it feels damp when squeezed, but does not drip. When the ratio is right, the temperature rises in the center and the smell is like forest soil, not rot.

How often should the pile be aerated?

Once or twice a week is usually enough for a backyard compost bin. The material is moved from the outside toward the center and turned with a pitchfork or a stick, without needing to turn the entire volume. In summer, with heat, activity is faster and it is worth checking more often; in winter the process slows down and there is no need to be as persistent. If the pile becomes compacted or waterlogged, aeration becomes the priority, because without oxygen odors appear and decomposition becomes anaerobic.

What should I do if odor or insects appear?

A sour or rotten smell almost always indicates too much moisture or too much green material. The solution is to add dry material, mix well, and let it breathe. If small flies appear, there are usually exposed fresh scraps: cover them with a layer of leaves or soil and bury the new material. Rodents, when they appear, signal that there are animal-based scraps or cooked food in view. In that case, remove what attracted them, turn the pile, and reinforce the compost bin enclosure. None of these signs is serious if corrected in time.

Home composting: what is and is not worth adding

If you want to comment on this article about home composting, add an observation from your own compost bin, or correct something that does not sit right with you, you can write to us by email. We read readers' letters and some are published in the community section, with your name if you authorize us to use it. The message does not need to be long: it is enough to tell us what materials you use, how you aerate the pile, and what results you have been seeing in your yard.

For agenda items, workshops, or guided visits to nearby farms, the same email works. If you prefer to call, we answer the phone.

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