Composting 101: 10 Questions Answered

There aren’t many downsides to composting. For starters, it’s good for the planet. By giving food scraps and yard waste a second life, it stays out of landfills (where 40 percent of all food in the U.S. ends up) and nourishes your garden instead. Plus, the rich soil is a natural alternative to chemical fertilizers, which is known to seep into groundwater and pollute local waterways. And the best part is you can start composting in your yard or kitchen anytime, leading to a more bountiful garden to enjoy—our FAQs and tips will show you how.

Composting 101

First things first, a few basics to lay the groundwork.

What is composting?

Composting recycles your kitchen scraps into garden fertilizer. For example, eggshells are one of those things that should not be put down the drain. But they can be composted! The almost-magical process takes what would have been food waste (like herb stems, potato peels, and ends of carrots) and transforms them into a nutrient-rich mulch that can be added to your garden soil.

What is compost?

Compost might look a lot like regular soil, but there’s more going on that makes it extra special. When your scraps—aka green matter—start to decompress, they break down into nutrients that plants need to thrive, like nitrogen, potassium, and phosphorus. When combined with brown matter, like dead leaves and branches, it adds carbon which gives these microbes energy, and nitrogen facilitates protein synthesis. Then, when these organic materials are exposed to air and water, microorganisms like bacteria, actinobacteria, fungi, protozoa, and earthworms start to break them down into compost. What you’re left with is a substance called humus, which basically looks, smells, and feels like dark, moist soil.

How to Compost at Home

Now that we’ve covered what compost actually is, let’s dig in to setting up your home routine.

Do I need a bin to make compost?

If you have an expansive yard and a large area to make an open-air pile, the answer is no. The rest of us (read: most of us) will need to invest in a bin to streamline the process and contain any completely normal but occasionally unpleasant smells.

You can really go down a rabbit hole when it comes to researching home bins and building them from scratch. If you’re just starting out, our advice is to keep it simple and order a large bin to place in your yard. Check with your city first—your local recycling program might offer them, or you can order one online.

Can I compost without a yard?

Definitely! Here are a few ways to approach it:

• DIY an indoor compost bin (Apartment Therapy has some great tips) and use it for indoor plants. You can also invest in a device like Lomi that turns your waste into compost with the push of a button.
• Collect scraps in a freezer bag and bring them to a local drop-off location (like the farmers’ market) once a week
  Some cities have green waste bins—check with yours to see if they offer a composting program.
• Check with local gardens that have compost piles—you might be able to bring scraps to an urban farm, school garden, or city-run program.

What can I put in the compost pile?

You’ll want to fill your bin with a combination of green and brown matter, layering them in the way you might layer lasagna.

Brown matter

These are generally “dry” ingredients that are rich in carbon.

• Cardboard
• Corn husks
• Cotton
• Dead leaves
• Hay
• Nutshells
• Paper
• Pine needles
• Sawdust
• Shredded newspaper
• Straw
• Twigs
• Wood ashes
• Wood chips
• Wool

Green matter

These tend to be “wet” and are rich in nitrogen.

• Algae
• Bread
• Coffee grounds and filters
• Dead plants
• Eggshells
• Freshwater aquarium water
• Fruits
• Fur
• Grains (cooked, plain)
• Grass clippings
• Hair
• Seaweed
• Tea bags
• Vegetables

What not to compost

These materials may be harmful to the health of your compost.

• Black walnut tree leaves and twigs
• Charcoal
• Dairy products
• Diseased plants
• Dryer or vacuum lint from synthetic fabrics
• Fats or oils
• Glossy paper (especially with color printing)
• Meat or fish scraps or bones
• Pet waste

How often should I turn a compost pile?

Turning the pile is technically optional—nature will do its thing regardless. However, regularly turning the pile (or using a turning bin) speeds up the composting process so you don’t have to wait as long to use the good stuff in your garden.

Can I compost year-round?

Definitely! The composting process will naturally slow down in the winter due to lower temperatures, and speed up in the warmer months when microorganisms eat faster. One way to prioritize composting any time of year is to put a small composting can on your counter. Once it’s full, you can transfer it to your outdoor pile rather than having to take out scraps whenever you cook.

What makes compost break down faster?

Creating compost doesn’t happen overnight, putting smaller pieces into your pile and regularly aerating it will speed up the process. Smaller pieces of food (like a chopped cabbage core instead of tossing it in whole) makes it easier for the microorganisms to attach and begin breaking the food down.

How can you tell when compost is finished?

Finished compost will look like dark, crumbly topsoil—not like the original materials you added—and should have a pleasant, earthy smell. To double check if it’s ready, you can use what Earth Matter calls “the bag test.” Add a handful of moist compost to a resealable bag and press out all the air; leave for three days. If you smell a sour odor after opening the bag, the microorganisms are still doing their work; retest in a week.

How should I use compost in my garden?

Here are a few different ways you can use up your compost:

• Replenishing soil: To replenish nutrients in your potted plants, add an inch of compost 1-2 times per year, or whenever you re-plant. For ground soil, work 1-2 inches of compost into the top 3-5 inches of soil.
• Growing flowers: In the fall, add a 1-inch layer of compost to protect your flower roots from freezing, and in the spring, loosen up the top few inches of soil and perennial beds and mix in a 1-inch layer of compost.
• Growing vegetables: Start in the fall by giving your vegetable garden plenty of compost (several inches on top of an existing bed). In the spring, you can till it into the soil.