A beginner’s guide to composting food waste

While we have a staggering amount of food waste to deal with in the United States each year, trashed grub can prove highly valuable. Food waste can be made into compost, a nutrient-rich substance farmers sometimes call “black gold” because of its ability to help plants thrive.  

While microscopic creatures like fungi and bacteria break down organic material out in nature, composting speeds up the process by creating the ideal conditions for these helpful organisms. It can be done everywhere from backyard bins to industrial-scale tanks, and is commonly performed in oxygen-rich (also known as aerobic) environments. All in all, composting comes with a long list of advantages when done right. 

What are the benefits of composting?

Composting helps both the environment and the economy because it helps divert trash, in this particular case food waste, from landfills and can make for more sustainable agriculture.

Composting reduces greenhouse gas emissions by helping sequester more carbon in soil and cutting down the methane that gets spat out of landfills. In those dense, oxygen-free trash heaps, waste like food releases loads of the powerful greenhouse gas that has nearly 30 times the heat-trapping power of carbon dioxide. In fact, wasted food causes nearly 60% of all methane emissions from municipal solid waste landfills.¹ According to an analysis published in 2022, diverting just half of the food waste that goes to landfill toward compost would cut 64.35 million tons of CO2-equivalent emissions, which is like taking nearly 13 million cars off the road.²

By redirecting these organic materials to agriculture, we can also fill the soil with nutrients and cut down on the need for fertilizers and pesticides (which can harm our health, the environment, and often rely on fossil fuels for shipping and production).³

Compost can also help conserve natural resources. It boosts soil’s ability to retain moisture and significantly reduces water demand. “Aerobic composting is amazing,” says Lily Pollans, an urban planner at Hunter College in New York City who researches municipal waste policy. “The food breaks down in an environment with oxygen and the end result is a high-quality soil amendment that can reintroduce the nutrients into the soil—it’s true circularity.”

Composting can also help draw attention to just how many meals and scraps we throw away. On average, U.S. households waste around one-third of all food they purchase—that’s around $240 billion hitting the bin each year.⁴

In addition to saving lots of cash, composting can create jobs. According to analysis from the Institute for Local Self Reliance, composting operations can create two times as many jobs as landfills and four times as many jobs as waste incineration.⁵

While compost does release some carbon dioxide as organic matter decays, it’s proportional to the amount that the discarded fruits and veggies absorbed up while growing. “It’s important to think about them being biogenic emissions,” says Callie Babbitt, a sustainability researcher at Rochester Institute of Technology. “When food is produced, this is the growth of plant matter that takes up carbon dioxide—so when it degrades, it’s a net-neutral action.”

How to compost food waste at home

While the process seems daunting, the whole shebang is relatively straightforward: Composting essentially consists of cycles of processing and piling up food waste, along with other organic materials such as leaves and twigs, and maintaining it until it’s ready for soil prime time in your garden (which doesn’t have to be huge to be successful!). 

Many public and private universities run continuing education programs and extensions to train people up on composting best practices. The guides from the University of Illinois Urbana-Champaign or the University of Florida are particularly good—as is this step-by-step YouTube playlist from Institute for Local Self Reliance. Definitely dig in and do your reading before you start a pile. In the meantime, these are the basics:

Step 1. Collect scraps

To set up your own DIY composting operation, you can start off by collecting food waste in a closed container. You can place it under the sink, on your kitchen counter, or in the fridge or freezer (this will make it less smelly and susceptible to curious pets or kids). Compost piles must contain two crucial components: roughly one-part nitrogen-rich “greens” that include many kinds of food waste, along with roughly three-to-four-parts carbon- or carbohydrate-rich “browns.” The latter includes dead leaves, twigs, shredded cardboard and non-glossy paper, brown bags, and untreated wood chips. These materials can be prepared for composting by breaking them into smaller pieces to help them break down more quickly.

Step 2. Start a pile

Once you’ve got the ingredients ready, it’s time to decide how and where you’ll build your compost pile. There are several methods to contain compost, such as using a bin, trench composting (i.e. burying waste into holes in soil, which can take around a year to break down), or placing it in a heap outside. The last option, however, can bring in pests since it’s not covered. Bins, however, can be made from a variety of materials, like cinder blocks, wood or wire.

The location of your composting operation depends on a few factors. If you’re looking to put it outside, the compost should be easy to access all year and have sufficient drainage. So try not to put it right next to a fence, and make sure you can access water nearby to regularly add to the compost if needed.

A note about vermiculture—or worm composting

If you don’t have a yard or outdoor space, vermiculture—or worm-powered composting—can be done indoors. This requires a container with a tight-fitting lid and some air and drainage holes, along with some bedding material and, of course, worms. As long as you take care of it correctly, it shouldn’t invite pests or stink up your home. This method is a little more advanced, so for now let’s stick to the more conventional approach.

Step 3: Maintain a good environment

Composting is an active process, so after your set-up is complete it requires some upkeep. The pile must remain at around 150 degrees Fahrenheit (compost thermometers are a thing, thankfully) to keep the decomposers working quickly and efficiently, ward off disease-causing organisms, and rid the compost of weeds.

You can help maintain a consistent temperature by turning and mixing your pile around every three to four days. This ensures oxygen reaches all those organic bits and pieces so that  decomposition can occur evenly throughout, rather than the center getting super hot. For a regular bin set-up, turning works like tossing a salad (a gardening fork or shovel should do the job). You can also get a special kind of tumbler that’s easy to rotate with a handle, rather than manually doing the work within a bin or outdoor pile.

All in all, it’s important to take great care of your compost not only to ward off pests and keep the soil free of disease and weeds, but also to reduce methane emissions. If your pile overheats, it can release the potent gas the same way landfills do. Still, it isn’t necessarily a major concern as long as you maintain it carefully.

Step 4: Watch and adjust

It’s also key to keep things moist—but not too moist. Your compost should feel like a wrung-out sponge, so be sure to add water if it starts to get dry. If your pile starts to stink, it could be too wet or lack enough air circulation. Adding more dry material and turning it should help. If your compost isn’t getting warm enough, you can add some greens and turn it.

Step 5: Harvest & cure

So when is it time to harvest your compost? It can take anywhere from two weeks to two years based on the materials you put in there, the size of the pile, and how regularly it’s getting turned. A bin of worms takes around three to six months, a standard bin kept at warm temperatures may take a month or two, and a leaf pile left alone can take longer than a year.⁶

At this point, it may be time to cure. This process, which takes at least four weeks, allows degradation to slow down and create more chemically stable compost—uncured compost can kill adjacent plants by modifying their environment. To cure it, you can move the oldest portion at the bottom of the pile to another area or simply cease adding new materials. You should also sift out things that didn’t fully break down, like twigs or eggshells (which can go back into a new compost pile).

Here are a few signs your compost is cured and ready for primetime (aka planting):

You can also try this easy test: Place a handful of moist compost into a zip-lock bag and press the air out before you seal it. Leave it for three days, and then check if it smells like ammonia or has a sour scent—that means it isn’t quite ready.

What kinds of food can be composted?

Lots of scraps that normally hit the trash can help your compost thrive. 

“Greens” break down quickly and offer nitrogen, a vital ingredient for plant growth, to compost. Here’s a few essentials to add to your compost pile, though you should consider saving these for stocks and smoothies, if at all possible:

“Browns” include:

While food waste does typically make for helpful compost, researchers have pointed out in recent years that toxic, non-degrading forever chemicals can make their way to agriculture through food waste in compost.⁷ But at the moment, it isn’t clear whether PFAS in compost are at concentrations that can harm human health.⁸

What should not be composted

Unfortunately, not all food waste is fit for the home compost pile. Some items take too long to break down, may attract animals, or must be processed at industrial facilities that can reach higher temperatures.

These at-home no-nos include:

Can biodegradable products go into my compost?

Biodegradable doesn’t always mean compostable, and it’s a term often applied to plastics that definitely don’t belong in your compost bin. For a material to deserve this label, it must be possible for decomposing bacteria and other organisms to break it down into simple substances like water, methane, and carbon dioxide. Truly compostable products are made from organic materials that can break down over time, but biodegradable products can receive this vague label even if they take centuries to break down in nature or require special processing in a facility.

Food waste composting programs in the U.S.

If you don’t have the space to compost at home, a state or community program might take those food scraps off your hands. Composting policies in the U.S. are set by states and cities, the latter having the most control over local food waste processing. In recent years, composting access has expanded significantly across the U.S.: Between 2014 and 2019, the number of communities with composting programs grew by 65%.⁹ More than 200 cities around the country offer curbside food scrap collection for composting. 

But overall, composting resources aren’t evenly spread throughout the country. Nearly half of all full-scale food waste composting facilities are located in just a handful of states, and California far outnumbers even the top locations. To see whether you have any composting programs near you (public or private), check out this website. You can also try the app ShareWaste to see if any neighbors are looking for food scraps to add to their home compost.

Where does food waste normally end up?

Unfortunately, more than one-third of the country’s food waste ended up in landfills, accounting for 24% of the castoffs in those trash heaps; only about 4% went towards compost.¹⁰ But cities and states around the country have passed or are looking into legislation to divert these nutrient-rich materials back to food-insecure households, composting, energy-producing facilities or other sustainable options.

What are other solutions to food waste?

While composting is one of the most straightforward techniques to deal with food waste, uneaten grub can also be sent to places including landfills, turned into energy and fertilizer via anaerobic digesters, or livestock operations as food for animals. Edible food can also be donated to organizations who send it to people in need—some states, such as Vermont and New York, require some businesses to donate excess edible food.

1. Quantifying Methane Emissions from Landfilled Food Waste, U.S. Environmental Protection Agency, Jan. 2024 ↩︎
2. How the US Economy and Environment can Both Benefit From Composting Management, Environmental Health Insights, 2022 ↩︎
3. Human Health Issues Related to Pesticides, U.S. Environmental Protection Agency, Oct. 2023 ↩︎
4. Estimating Food Waste as Household Production Inefficiency, American Journal of Agricultural Economics, Mar. 2020 ↩︎
5. Pay Dirt, Institute for Local Self-Reliance, May 2013 ↩︎
6. Cornell Composting, Cornell Waste Management Institute ↩︎
7. Per- and Polyfluoroalkyl Substances (PFAS) in Commercial Composts, Garden Soils, and Potting Mixes of Australia, Environmental Advances, Apr. 2022 ↩︎
8. Emerging Issues in Food Waste Management: Persistent Chemicals, U.S. Environmental Protection Agency, Jan. 2022 ↩︎
9. Composting in America, U.S. PIRG Education Fund, Frontier Group, 2019 ↩︎
10. 2018 Wasted Food Report, U.S. Environmental Protection Agency, Nov. 2020 ↩︎