A Guide to Composting: Turn Food Waste Into Garden Gold

Millions of tons of food waste, yard debris, and paper products are sent to landfills each year in the United States, which will degrade over time to produce around the same amount of methane as about 22 million passenger vehicles produce in a single year.

Methane is a greenhouse gas that is 28 to 36 times more effective at trapping heat in the atmosphere than carbon dioxide, and every time you toss an apple core, overripe banana, bruised tomato, or wilted basil in the trash, not to mention piles of grass clippings, newspapers, and cardboard, you're adding to the problem: the more waste that ends up in landfills, the more methane that's produced. And while diverting waste away from landfills in any way can help, composting is one way where you can immediately become a part of the solution. If you have a garden, it also produces something that you can use.

"Composting turns waste into resources," explains Rick Carr, master composter and farm director for Rodale Institute. 

What Is Composting?

Compost is essentially decomposed organic matter that's used as a soil amendment, improving soil by increasing its moisture retention and adding in beneficial bacteria and nutrients. Compost can increase plants' resistances to pests and disease, thereby reducing the use of pesticides, and because of its beneficial properties, it also reduces reliance on fertilizers.

To make it, food waste, yard debris, and paper products are combined in a pile and left to sit, with regular mixing, to create a favorable environment for microbes to break down the collected material over time. Food waste is a source of nitrogen; the yard debris and paper are sources of carbon; and, when combined in the correct ratio and left in an oxygen-rich environment, microorganisms begin feeding on the mix, which in turn heats everything up, further speeding up the process. After about a year or two, all that waste material is transformed into a nutrient-rich soil amendment. As Melissa Tashjian, founder of Compost Crusader, says of the process and the product: “It's magic.”

It's also easy. You can compost waste in your backyard (if you have a backyard) or under your sink, or you can participate in a community composting program. Many municipalities have composting programs in which all that's required of you is to fill up a green bin and put it out on the curb each week. And while it isn't a solution for food waste—if you're throwing edible food in the compost bin, it's still technically "food waste"—it is a solution for what to do with food waste that happens to have benefits that extend beyond simply reducing the amount of greenhouse gas emissions produced in landfills.

"The more compost you produce, the more you can add to soils, which means you grow better food," explains Sally Brown, PhD, research professor of environmental sciences at the University of Washington. “Our food scraps are low-hanging fruit…if you have a moldy orange or a soft apple, it's no longer food for you, but it can be food for the microbes in the soil."

Despite a growing awareness of the importance of diverting organic material away from landfills and the benefits of composting stuff you're throwing into the trash, making a habit of the practice might seem intimidating or complicated, but with a small amount of effort and a little consideration, it couldn't be easier.

How to Get Started With Composting

You can't start composting without a compost bin. Big box stores and online retailers sell compost bins in materials such as plastic, wood, and steel that range from functional to fancy. You can have a compost bin delivered to your door, or you can make one from pallets or other upcycled materials. 

Before you buy one, the first thing you have to consider is its size. For most homes with outdoor space, the ideal size for a compost bin is three feet high, three feet wide, and three feet deep, according to Carr. This size is large enough to ensure that the pile contained within the bin has ample surface area and enough space to encourage the movement of air, which helps to regulate the temperature inside at about 120 to 150° F, which must be maintained for the waste to be broken down efficiently. If your bin is too small and the movement of air is impeded, it may overheat, interfering with the microbial activity that transforms the waste into a soil amendment.

Once you have your bin, set it up in a level area with well-drained soil and at least partial shade. Too much exposure to the sun, Tashjian explains, will dry the contents of the bin out, and that’s bad because the microorganisms that will break down the waste depend on that moisture to survive. On the other hand, if there’s no place for excess moisture in the bin to drain away, the contents can become waterlogged, killing off some of those beneficial microorganisms and potentially creating conditions in which foul odors will be produced.

With your bin set up, you have to start filling it, but you can’t just throw anything in there. Compostable material is divided into two categories: green and brown. Food waste falls under the "green" category, while things like sawdust, leaves, grass clippings, and shredded newspaper fall under "brown." And you want to add these things to the bin in a ratio of two parts brown material for every one part of green material. "For every one-gallon bucket of food scraps, you need to cover it with at least two one-gallon buckets of brown materials," Tashjian says. 

If you're adding green items that contain a lot of moisture—think tomatoes and watermelons—you'll want to increase the brown-to-green ratio to compensate; Carr suggests a three-to-one ratio of brown to green items when you've got very watery green items.

What to Compost

• Fruit and vegetable scraps
• Coffee grounds, including the filter
• Bread, pasta, and baked goods
• Rice and other grains
• Beans, nuts, and seeds
• Eggshells
• Meat
• Bones
• Yogurt, milk, and other dairy products
• Dried leaves 
• Grass clippings
• Straw and hay
• Newspaper and other non-glossy papers, torn into pieces
• Cardboard, torn into pieces

Do not add these items to the compost bin:

What NOT to Compost

• Weeds
• Plastic
• Waxed cardboard (e.g. the containers used for milk, soup broth, and wine)
• Coated paper or cardboard (e.g. cereal boxes)
• Metal
• Glass

There is some disagreement about adding animal products like meat, bones, and dairy products to the compost bin. Carr gives these items the green light, but with a word of caution. "Meat, dairy, and eggs have a greater potential to produce odors and attract pests," he says. However, Carr says that both of those issues can be eliminated by following the "no food showing" rule of composting: Whenever you add food scraps of any kind, cover them with a layer of brown materials.

Composting isn't a toss-and-ignore process; it requires active management. Your compost pile should be "turned" at least once per week, says Tashjian; essentially, you have to use a pitchfork or shovel to incorporate the ingredients—just like tossing pasta in sauce. Turning the pile helps distribute moisture and introduces oxygen, both of which will help your compost pile break down faster and prevent foul odors.You'll know it's ready when your old banana peels, apple cores, and leaf mulch look like rich, black dirt.

The temperature within your composting bin, the mix of what it contains, and the frequency with which you turn its contents will influence how long it takes for the material inside to break down into compost. A compost bin located in a hot, arid climate that's filled with the ideal ratio of green to brown and turned each week will break down much faster than a bin set up in a cold, wet climate with too much green material that's turned every other week. On average, Carr believes it'll take at least one year for your banana peels and newspapers to transform into black gold.

Vermicomposting: A Solution for Small Spaces

No room for a backyard compost bin? Vermicomposting is a good, small-space composting solution. In this set up, also called a worm bin, you put red wiggler earthworms in a small container that you keep in the kitchen (people often tuck them under the kitchen sink). You feed them food and yard scraps, still maintaining an ideal green-to-brown ratio, and the wiggling workers break it down into compost.

Tashjian admits that vermicomposting isn't for everyone. You might be grossed out by the idea of sharing your living space with worms or unwilling to maintain a bin full of living creatures in the kitchen. It's also not a good option for diverting larger quantities of food waste. On average, vermicomposting takes three to six months. While that may sound like a lot less time than outdoor composting, it's actually a relatively long time given that an under-the-sink bin only holds a fraction of the compostable material of a three-foot cube.

"Worms can only eat so fast," Tashjian says. "One of the biggest reasons worm bins fail is overfeeding."

Failing to maintain the correct ratio of green and brown materials in an under-the-sink bin also increases the odds the bin will smell or attract flies—not something you want in your kitchen. Indoor vermicomposting is best suited to a single person who doesn't produce much waste and is committed to treating the worms like odd little pets that need regular care.

Community Composting

While backyard composting is a DIY process, Tashjian acknowledges that tending to a backyard compost pile is not an interest (or a priority) for everyone. Community composting was designed to offer an alternative. 

Community gardens, businesses, nonprofits, or local farms often operate community composting programs. You can have your waste materials picked up or you can drop them off at the site and they manage the actual process of composting. As a bonus, the finished compost is often returned to the community, added to community gardens to promote local foods, or used in stormwater management or soil remediation projects. 

Compost Crusader operates a community composting program in Milwaukee. Tashjian provides homeowners and businesses with bins and picks them up on a regular basis to be composted at local facilities. The company diverts 250,000 pounds of food waste from the landfill every month—and that's just in Milwaukee. 

Many municipalities have also committed to composting, offering curbside composting programs, along with bins to put those materials in, to residents, similar to the way trash and recycling are managed. Some states have gone further; for example, Vermont passed a state law that bans sending food scraps to the landfill; California, Connecticut, Massachusetts, Oregon, and Washington have similar laws, according to the U.S. Composting Council. 

"It's good to have municipal collection available," says Brown. "Not everybody needs to [compost] on their own but everybody needs access."

Several of these programs were postponed during the pandemic but, Brown notes, that most have come roaring back. If you've considered composting or are looking for ways to reduce your environmental footprint, it's a good time to get started.

"Taking food scraps out of the landfill is something everyone can do and it has an immediate benefit," says Brown.