Most of what goes into U.S. landfills is organic waste, ranging from household food scraps to yard trimmings. That's a problem because in that environment, organic waste is deprived of oxygen, which helps break material down.
The result: , a potent greenhouse gas that contributes to global warming.
Consumers can curb their environmental impact by composting, which helps break material down in ways that reduce the release of methane. This can be done whether someone lives in a home with a yard or in an apartment without outside space. Composting also alleviates pressure on landfill space and results in a nutrient-rich substance that help soil.
Robert Reed, with the recycling and composting company Recology, said that applying compost makes soil better at retaining moisture, which makes it resilient against droughts, wildfires and erosion.
For people who want someone else to compost their food scraps, some local governments offer curbside pickup. Otherwise, nonprofits, farmers markets and community gardens often fill that gap. Companies in some areas also will pick up the food waste to be taken away for composting for a fee.
For those who want to try , here's how to .
If you’ve got a yard
Composting doesn't necessarily require much space. Even 4 square feet — roughly the size of a standard office desk — can do the trick. Common receptacles include open wooden bins or large barrel-shaped tumblers that you can rotate on a metal rod. Free-standing piles also work.
Some people follow a strict schedule of turning the pile, often with a hoe or shovel, or adding to it regularly. Backyard composting typically relies on microbes to break down the waste, which can bring a pile's temperature up to 130-160 degrees Fahrenheit (54-71 degrees Celsius). Others follow a more passive approach.
Experts break the composting recipe down into four main ingredients: water, oxygen, nitrogen-rich “greens” (food scraps, grass clippings) and carbon-rich “browns” (cardboard, dead leaves, shredded paper). Typically compost has two or three times as much “brown” material as “green.”
The Environmental Protection Agency meat, bones, dairy, fats and oils in backyard compost piles because they typically don't get hot enough to fully break them down, and because they're more likely to attract pests. The agency also says to steer clear of treated wood, glossy paper, pet waste and compostable dishware or bags.
Experts say composters can experiment with what works and what doesn't. Rodale Institute Senior Farm Director Rick Carr said he's tried animal products and just about everything in his household. Hair from the hair brush and fully cotton swabs break down great. Cotton T-shirts? Not at all.
“If you’re unsure if it’ll break down, put it in there and you’ll find out,” he said.
The bacteria and fungi feed on the pile of organic waste and turn it into compost. The finished product looks like moist, dark soil. The EPA says a well-tended pile can produce finished compost in three to five months, while a more passive pile that doesn't reach high temperatures may take up to a year.
Bob Shaffer, who owns a company called Soil Culture Consulting, said that for him, the process can take closer to nine months, but it's easy to tell when it's finished.
"When you look at compost, what you should not be able to see is, oh, there’s a leaf. There’s that carrot top that I put in there 10 months ago. You shouldn’t be able to discern what the material is," he said.
Common pitfalls
Most composting problems happen when the ingredients get out of whack.
One way to make sure you’ve got the right balance of “greens” and “browns” is a “squeeze test,” by reaching into the pile and grabbing a handful then letting it go, said Nora Goldstein, editor of the organics recycling magazine, Biocycle.
“If it just kind of crumbles off your hand, it’s too dry. If you squeeze and get a little bit of drips, it’s a little wet. But what you want is to squeeze it, let it go, and have kind of a coating on your hand.”
When the pile gets too dry, the composting process slows down or stops. The answer: Hose it down or add more food scraps.
Another common problem is the opposite: there isn’t enough air, or there are too many nitrogen-rich “greens.” The first sign of trouble is when the compost pile smells. That typically means the microorganisms are dying and the pile is releasing methane, like in a landfill. The solution: stir the pile to get more air inside and allow it to cool down. Then add some cardboard or paper. A pile that's too wet can also attract flies, maggots and rodents.
“As long as you’re mixing in enough amendment or browns, you’ll stay out of trouble,” Goldstein said.
If you lack outdoor space
Composting indoors is possible through what's known as vermicomposting, a process that relies on worms. People can buy premade worm bins, make their own out of untreated wood or use plastic storage bins with a few modifications, according to the EPA. The containers should have tight-fitting lids and keep out the light. Only certain types of worms will work, and they can be obtained from a worm grower or a neighbor who's already started vermicomposting.
Goldstein said that the process isn't always easy: “You really have to know what you're doing.”
Instead of relying on microbes, worms feed on the carbon- and nitrogen-rich organic matter. They poop out almost-black castings. That's the finished product. The EPA says it takes about three to six months, which can be faster than backyard composting. They can create a more nutritious end product than in traditional compost.
But Goldstein said that it can be tricky to ensure conditions are right for the worms.
“You want to make sure those worms are very happy, because if they’re not, they will leave the bin. And they’re not harmful, it’s just a little freaky," said Goldstein.
Traditional composting, whether indoors or outdoors, is typically a process that takes place over months, not days, Goldstein said. Electric countertop devices that promise to break down food in hours or days don’t use the same process. Goldstein said those devices produce material that can be used in gardens, but it’s “not completely broken down” and should be mixed with soil.
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