Compost 101

Composting at home is easy – with a little know-how, keeping your compost pile efficient, odorless and pest-free is a cinch. Healthy compost piles are moist, warm and free of foul odors, so recognizing an unhealthy pile is not super challenging – and proper maintenance will quickly become second nature.

These basic principles will help you turn your food scraps and other materials (paper towels! Newspaper!) into a healthy, functioning compost pile.

The Carbon/Nitrogen Ratio

Scraps to compost fall into two basic categories: carbon-rich “browns” and nitrogen-rich “greens.” You need more carbon in your mix than you need nitrogen, with an optimum carbon/nitrogen ratio of about 30:1. If there is too much carbon (browns), decomposition will slow down. If there is too much nitrogen (greens), your pile may end up a little…pungent.

Generally, meeting this ratio means adding about one part brown for every two parts green, giving the decomposers a balanced diet with enough energy and nutrients to eat through everything you compost.

Carbon-rich “browns” tend to be dry, woody materials. Nitrogen-rich “greens” are usually colorful (think fruits and veggies) and usually a little moist. Here are few examples:

Browns (Carbon-Rich)

• Dried leaves
• Sawdust and woodchips (make sure these are from untreated wood)
• Shredded black and white newspaper
• Egg cartons
• Cardboard
• Dead, dried-out plants (disease-free)
• Tree bark
• Straw
• Peanut shells

Greens (Nitrogen-Rich)

• Fruit and vegetable kitchen scraps
• Coffee grounds and tea bags
• Green garden cuttings
• Fresh leaves and flowers
• Grass clippings

The carbon/nitrogen ratio balancing act can be as simple or complicated as you like. The easiest approach is to stick to the basic 2:1 (two parts green to one part brown) recipe. But if you’re striving for optimal compost efficiency, or want to achieve a specific soil quality for your gardening needs, check out The Compost Info Guide to find the exact C/N ratios for a wide variety of compostables.

Adding Material to Your Compost

For maximum efficiency, shred or chop food scraps before adding them to your compost whenever possible – the smaller the pieces, the faster and more effectively your compostables will decompose. When you add yard trimmings, for instance, use clippers to cut stems into shorter lengths. Likewise, you can crush egg shells and chop up veggie scraps, fruit cores and peels. Always rip apart newspapers, cardboard and paper egg cartons before composting to distribute the carbon content more evenly.

Because you need to add browns (carbon) to your compost every time you add food scraps and other greens, it may be handy to keep a container of dry, carbon-rich materials near your compost pile/bin.

Turning Your Compost

Periodically turn your compost with a pitchfork or shovel (or a special compost crank!) so the new material ends up on the warm interior of your compost pile.

Turning your compost also infuses your pile with oxygen (also known as “aereation”), which is essential for the aerobic bacteria that help decompose material. If you have not added materials to your compost heap in a while, make sure you still turn the compost every so often. If the material gets too dry, you can water it with a hose (moisture content should be about 50 percent) to maintain the moisture that the composting microbes need.

Other Tips for Healthy Compost

Compost Not Warming Up

Compost needs to get hot so that material breaks down sufficiently – depending on the size of your pile, temperatures can be as hot as 115F to 180F!  If your compost pile is well maintained but not warming up, here are some tips:

• Try adding more browns. Carbon is an energy source that bacteria will devour, heating up their environment.
• You can also try covering your compost to retain more heat. Add a layer of dirt, straw or other browns to trap heat. (Covering has the added benefit of deterring bugs around your pile.)

Compost Odor

Smells are a bad sign for your compost. If you avoid adding meat and oily foods to your pile, which can attract pests, your compost should not give off odors. Strong, foul smells usually indicate that the aerobic bacteria in your compost are struggling for one reason or another. Remedy your compost’s stench with these quick pointers:

• Turn your compost: You may have a heap full of stinky anaerobic bacteria if you are not turning your compost frequently. Try turning your compost every few days to infuse the pile with oxygen so that odor-free aerobic bacteria thrive and anaerobic bacteria do not.
• Add more browns: If your pile smells like ammonia, you’ve added too much green. Try adding more browns for each part green to for a balanced carbon/nitrogen ratio.
• Top with dirt: You can prevent smells by adding an extra layer of dirt or other brown covering over the top after turning and mixing in more browns.
• Avoid meat or oils: If you don’t mind attracting wildlife to your yard, you can feel free to include meats and oils in your compost. It’s wise to avoid these items, however, if your compost is close to your home or if you live in an urban or suburban area.

Still have questions? You can learn more about the science of composting and how to troubleshoot with the New York City Master Composter Manual or SyracuseCOE’s Superior Compost guide. Also, check out City Farmer’s Compost Hotline for expert support! Never give up on your compost pile! If something goes wrong, you can usually set things straight in a few days.

What to Compost and How to Do It

Dumping food waste and other organic matter into landfills just doesn’t make sense. Trapped under layers of garbage, these materials not only release massive amounts of pollutants such as methane, they also become unavailable where they’re needed most – back in the soil.

Composting instead of trashing food waste and other organics slashes environmental impacts and transforms otherwise squandered scraps into a useful resource. Dark, moist, nutrient-rich compost is a perfect fertilizer, free of pollutants, chemicals – and cost! For green thumbs and local farmers, compost adds invaluable organic structure and nutrients to the soil, and for everyone else, healthy soils mean better food and a healthier planet.

Whether you keep your own compost pile, are lucky enough to have municipal curbside composting, or drop off your scraps at a composting facility, you’ll need to know what to compost – and what to avoid adding to the compost pile.

What Exactly Can You Compost?

Food scraps, yard trimmings and paper products are the most common ingredients used to feed compost heaps – but plenty of other organic waste can be added, too.

As a rule, any item that was once alive or was derived from living matter can be composted. However, there are reasons to limit what you compost, particularly because the types of materials you use can optimize decomposition, deter pests and keep things from getting stinky. Avoiding toxic, diseased, chemical-contaminated wastes is also important.

Good Scraps for Composting

Whether you’re composting in your backyard, or sending scraps to a municipal compost operation, some items are nearly always acceptable for compost. Here’s a list of common items you can toss in your compost pile without a second thought:

Food Scraps

• Fruit and vegetable peels and scrap
• Plate scrapings (excluding meat, bones, dairy products, oils and greasy foods – see below)
• Egg shells
• Tea bags (remove the staple!)
• Coffee grounds and filters
• Grains (breads, cereals, rice, pastas, etc.)
• Nut Shells
• Fruit pits
• Bottle corks

Yard Trimmings

• Leaves, straw, pine needles
• Fresh or dried grass (as with all items on this list – chemical-free only)
• Flower and plant clippings
• Weeds that have not gone to seed
• Houseplants and potting soil
• Wood ash

Paper Products

• Paper items (napkins, paper towels, shredded brown bags, etc.)
• Shredded cardboard boxes
• Shredded black and white newspaper
• Non-glossy junk mail
• Bedding from hamster/gerbil/rabbit cages
• Paper coffee filters

Possible No-Nos for Municipal Composting

While most big, municipal composting programs can handle nearly any compostable, those managing smaller compost operations may wish to exclude some organics, such as meat, dairy and fish, since they’re slower to degrade, may smell and can attract animals.

If you have your own compost pile, you can decide for yourself what to add – but community compost programs often have rules about what you can include. Check out the rules before you throw in items like meat, fish, bones, fats, oils, dairy products and eggs.

Bad Scraps for Composting

Don’t put inorganic materials in your compost! While this may seem obvious, sometimes scraps can be contaminated with synthetics that can mess up the composting process, so take extra care. Any garden bits that may have come in contact with pesticides, weed killers or other inorganic products should be avoided, for instance. Additional common items to avoid include plastics, medicines, colored paper and cleaning chemicals.

For more guidance on what you can compost, take a look at this list of 100 compostables and visit the Can I Compost This? website. You can also contact your local composting center for donation regulations.

The Freezer or Fridge: Freezing and refrigerating compostables has one major perk: No matter how late you are “taking out the compost,” frozen scraps will never decompose and refrigerated scraps will be virtually odorless, so you’ll never need to worry about smells or attracting unwanted guests.

Under the Sink or On the Counter: If you don’t have room in your freezer, or will be discarding waste every few days, storing kitchen scraps under your sink or on your counter may be a convenient option. To keep scraps tidy between the time you save them and the time you actually dump them on a compost pile, you’ll need a container that’s easy to keep clean, seal and store out of the way. Look for containers at kitchen supply stores or check to see if your local government provides home composting equipment.

Clean and Simple Collecting

Chop up bulky scraps to get the most volume out of your bag or bin. Another option to reduce your volume is to avoid composting leftovers or preparation waste altogether. You can find plenty of recipes for reusing leftovers and commonly discarded, yet perfectly edible scraps like kale stems and broccoli stalks online. Check out our post on reducing food waste using mobile apps to cut your food waste and limit your compost needs.

If you keep your scraps at room temperature, fruit flies are bound to make an appearance every so often. Peelings, especially from fruit, often harbor fruit fly eggs, so refrigerating ripe produce and freezing the peels as soon as possible can help deter flies. To keep flies at bay in your countertop bucket, try lining your bin with newspaper or soiled paper towels to reduce moisture. You can also sprinkle small amounts of baking soda to curtail odors, add melon cuttings to your collection or rub vinegar along the top of your container. The best way to avoid flies and smells, however, is to freeze your food scraps – or simply take your compost out regularly and wash the reusable container every time.

From the kitchen to the compost pile, saving organic waste is easy and can divert tons of valuable material from the waste stream.