The Basic Rule: Brown and Green Materials in Layers
Compost works when you mix two types of material: browns (dry, carbon-rich items like leaves and cardboard) and greens (wet, nitrogen-rich items like food scraps and grass clippings). The bin needs both to break down properly. A rough target is three parts brown to one part green by volume, though exact ratios are forgiving—most home compost piles work fine as long as you have some of each.
Layer them as you add material. Put down a few inches of brown, then a few inches of green, then brown again. This layering speeds decomposition because it creates air pockets and mixes the materials that microbes need. If you dump all your greens in one spot and all your browns in another, decomposition slows and you may get odor problems.
Key Takeaways
- Browns include dry leaves, shredded cardboard, straw, and wood chips; greens include fruit and vegetable scraps, grass clippings, and coffee grounds.
- Never add meat, dairy, oils, pet waste, or diseased plants—these either attract pests or introduce pathogens that survive composting.
- Chop or shred larger items before adding them so they break down faster and don't create dense clumps.
- Keep the pile moist like a wrung-out sponge and turn it every week or two if you want finished compost in two to three months; passive piles take six months to a year.
Greens: Nitrogen-Rich Materials That Speed Decomposition
Greens are the "wet" materials that heat up the pile and feed the microbes doing the work. Kitchen scraps are the most common: fruit and vegetable peels, cores, seeds, and trimmings all break down quickly. Coffee grounds and tea bags (remove the staple from tea bags first) add nitrogen and moisture. Grass clippings work well if they have not been treated with herbicide—always ask before taking clippings from someone else's lawn.
Plant trimmings from your garden, including wilted flowers and pulled weeds, go in the green pile. Fresh manure from herbivores (horse, cow, chicken, rabbit) is excellent if you have access to it, though it heats up fast and can smell strong—bury it under browns to manage odor. Avoid diseased plants or weeds with mature seeds, because home compost does not get hot enough to kill either.
Browns: Carbon-Rich Materials That Build Structure
Browns are the dry materials that give the pile its skeleton and balance the nitrogen in greens. Fallen leaves are the easiest source—shred them with a mower or by hand if they are small. Shredded cardboard and newspaper (black ink only; colored inks may contain heavy metals) break down well and add bulk. Straw and hay work, though hay may contain weed seeds that survive composting.
Wood chips, sawdust, and untreated wood shavings are browns, though they decompose slowly—use them sparingly or save them for the bottom layer to improve drainage. Paper bags, paper towels, and cardboard egg cartons all work. Avoid glossy paper, wax-coated cardboard, and anything with plastic coating, because these do not break down in a home pile.
What Never Goes in the Bin
Meat, fish, bones, and any animal products besides manure attract rats and raccoons and create odor that neighbors will notice. Dairy (milk, cheese, yogurt) does the same. Oils and fats coat other materials and slow decomposition. Diseased plants introduce pathogens that survive the pile and spread to your garden—if you are unsure whether a plant is diseased, leave it out.
Pet waste (dog or cat feces) contains pathogens harmful to humans and should never go in compost you plan to use on vegetables. Treated wood, charcoal, and coal contain chemicals that persist in finished compost. Glossy or coated paper, plastic, and synthetic materials do not break down. Weeds with mature seed heads may survive and spread when you use the finished compost.
Speeding Up Breakdown: Size and Moisture Matter
Smaller pieces decompose faster because microbes have more surface area to work on. Chop vegetable scraps into pieces smaller than a walnut. Shred cardboard and leaves instead of layering them whole. Break up clumps of grass clippings so air can reach the center. A pile of whole leaves takes months; shredded leaves take weeks.
Moisture is as important as material type. The pile should feel like a wrung-out sponge—damp throughout, but not dripping. If it smells like ammonia or rotten eggs, it is too wet; add browns and turn it. If it is not heating up and nothing is breaking down, it is too dry; add water or greens. Check the center of the pile by pushing your hand in; if the outer layer is moist but the center is bone-dry, turn the pile to redistribute moisture.
Active Versus Passive Composting Timelines
Active composting means turning the pile every week or two. This speeds decomposition to two to three months because turning adds oxygen, which microbes need. You will see the pile shrink visibly and heat up (the center may be too hot to touch). This method works well if you have the space and the time to manage it.
Passive composting means adding material and leaving it alone. It takes six months to a year, but requires almost no work. You straightforward layer browns and greens, keep it moist, and wait. This works fine for most home gardeners—the finished compost is the same either way. Choose based on your schedule and how soon you need the finished product.
Frequently Asked Questions
Can I compost citrus peels and onions?
Yes, both break down fine. Citrus peels take longer than softer scraps because the skin is tough, so chop them smaller. Some gardeners worry that citrus and onions repel worms, but in a hot pile (above 120°F) there are no worms anyway—they live in cooler, passive piles. In a passive pile, add them in moderation mixed with other materials.
What about bread, pasta, and cooked food?
Uncooked bread and pasta are fine—they are just carbohydrates and break down like any plant material. Cooked food, especially with oil or sauce, can attract pests and create odor. If you want to compost cooked scraps, bury them deep in the pile under several inches of browns so they are not visible to rodents.
Do I need to add compost starter or worms?
No. Microbes and fungi are already on the materials you add—you do not need to buy anything. If you want to speed things up, add a shovel of finished compost or garden soil to introduce established microbes, but it is not necessary. Worms are optional; they help in passive piles but are not required.
Can I compost glossy magazines or junk mail?
Magazines and junk mail have glossy coatings and inks that do not break down in home compost. Stick to plain cardboard, newspaper with black ink, and paper bags. When in doubt, leave it out—the finished compost is not worth contaminating with unknown chemicals.
What if my pile smells bad?
A rotten-egg or ammonia smell means the pile is too wet or has too much green material. Turn it, add dry browns, and reduce how much green you add next time. A compost pile should smell earthy, not foul. If it smells bad after you fix the moisture, you may have added meat or dairy by accident—dig it out if you can find it.