Look, it happens. You’re cleaning out the fridge, and you encounter a bag of mushy grapes, some wilted spinach, or a rotten half-head of cauliflower hiding in the back that you never got around to eating. After the momentary pang of guilt washes over you and the frustration of having to (yet again) throw away past-due produce you paid for subsides, you proceed to toss the spoiled items into your trash bin.
Next time, before you chuck it out, you may want to reconsider doing so—or rather, where you do so. Instead of the garbage, toss spoiled ingredients, foods scraps, and leftovers into your compost bin.
Food waste that ends up in landfills can contribute to alarmingly high quantities of methane gas emissions harmful to the environment. According to the United States Department of Agriculture (USDA), about 30-40 percent of the food supply in the U.S. turns into food waste. Food waste is also the third-largest source of human-related methane emissions in the country, accounting for approximately 14.1 percent of America’s emissions in 2017.
There is much work to be done in regards to curtailing food waste, starting with preventing it from happening in the first place. Composting food scraps and other spoiled ingredients is one great way to help offset the impact of your own wasted food on the environment.
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Whether you have a well-developed green thumb or are just getting into gardening, composting can help cut your costs and keep your beloved plant babies thriving—all while reducing harmful methane emissions caused by wasted food. To make composting a breeze, we’ve gathered the best foods for compost, plus other fodder that can supply your garden and the planet with vital nutrients for rejuvenated growth.
The 9 best foods for compost
Fruits
Most fruits—from apples and bananas to pears, grapes, and berries—provide compost with plenty of nutrients that will enrich your soil. Typically most varieties are safe to add, depending on the type of composting system you have at home, though there are some fruits that are better for composting than others. According to Jennifer Jewell, author of The Earth in Her Hands: 75 Extraordinary Women Working in the World of Plants and host of the award-winning radio program and podcast, Cultivating Place: Conversations on Natural History and the Human Impulse to Garden, “If you have a small space and you are using traditional outdoor composting methods—rather than vermicomposting, which uses earthworms in a bin—you might want to avoid fruits and vegetables that have very tough rinds or large seeds.”
Fruits with large seeds like avocados and stone fruits (including peaches and nectarines) can take a long time to decompose and might not break down at all. It’s fine to compost the fruit itself, but when possible, remove the pit. Additionally, certain fruits that are highly acidic, like citrus fruits and tomatoes, may harm the pH levels of vermicompost bins.
Vegetables
Scraps from vegetables are some of the best foods for compost. And yes, go ahead and compost them in any form: Raw, cooked, or rotten. When cooking at home, making a habit of reserving scraps (like the top portion of leeks or the kale stalks for your compost) can help reduce your food waste footprint.
Nuts and Grains
Nuts, nutshells, and grains will all greatly benefit your compost ecosystem, as each of these can impart important nutrients in your soil. Though items like tough pistachio shells may take several years to decompose, crushing them before adding them to the bin can help speed up the process and meld into the soil more uniformly.
Leftovers
In recent years, commercial composting bins have become more commonplace in businesses, especially in restaurants. According to the Natural Resources Defense Council (NRDC), U.S. restaurants generate an estimated 22 to 33 billion pounds of food waste each year. But composting leftovers in your own kitchen is an excellent idea as well, even if you’re cooking in a smaller scale. Go ahead and discard all your undressed vegetables, grains, and pasta, as well as boneless pieces of lean meat and protein. Jewell does recommend limiting things like “dairy, oils, dressings, or other fats to avoid impeding the decomposition and lively microbial activity.” Additionally, the Environmental Protection Agency (EPA) also recommends limiting meat or fish bones and scraps, as they create odor problems and attract pests such as rodents and flies (more on this below).
Coffee
Instead of throwing away the coffee grounds from your daily cup of coffee, Jewell recommends adding them—and unbleached paper coffee filters—to your compost to help add nitrogen into the mix. Both the coffee grounds and filters will quickly decompose within a few months in an active composting system. Some gardeners also suggest checking with your local coffee shop to see if they’re willing to donate any used coffee grounds they no longer need for your composting purposes. (Win-win.)
Tea
If drinking tea is part of your everyday routine, you may want to consider saving the steeped tea bags to toss into your compost bin. Nutrient-rich with minerals like potassium, phosphorus, and nitrogen, tea leaves can help maintain moisture levels, boost oxygen levels, and increase the speed of decomposition. Note: It’s important to make sure your tea bags are made from biodegradable, compost-safe materials before adding them to your compost.
Eggshells
Using eggshells in compost adds minerals like calcium and other essential nutrients that are beneficial for plant growth, making this scrap one of the best foods for compost. Though it isn’t necessary to crush the shells before adding them to your composting container, Jewell recommends doing so, as it helps speed up how quickly they break down.
Plant leaves
To help balance out the damp, green, and high-in-nitrogen materials from household leftovers, Jewell suggests adding drier, carbon-rich yard waste like dry leaves, plant trimmings, and old soil to your compost. Balancing the moisture and organic materials used will help prevent the compost from rotting, or becoming overly stinky, anaerobic, or dominated by bacteria.
Foods you should avoid composting
Though most foods are safe to compost, others may invite unwanted pests or lead to undesirable scents in your home. As mentioned, according to the EPA, dairy and/or animal products such as butter, milk, sour cream, yogurt, and eggs can create odor problems and attract pests. Additionally, they note that fats, grease, lard, or oils and meat, fish bones, and scraps can also potentially lure rodents and flies. Never compost any charcoal or char from your grill. Lastly, avoid adding any food waste that is potentially contaminated with harmful pathogens or bacteria that can disrupt the health of your compost. This applies to animal waste from pets, too.
What are indicators that your compost is ready to use?
“Once your compost feels, looks, and smells like crumbly, rough ‘soil’—and not like the food scraps or plant waste you originally put into it—it’s ready to use,” Jewell says. “The final product should maintain and drain water equally well and have good tilth. This means it holds together when damp and when squeezed in your hand, but it crumbles apart when you gently work it. Lastly, it should smell earthy,” Jewell notes.
How much compost should you introduce at a time to your garden or plants?
Indicators like the color of the leaves and the formation of flower buds can help identify a plant in need of a nutrient boost, Jewell explains. Introducing your homemade compostable scraps can help give your plants and garden the nutrients they’re lacking.
“I add a good two inches of compost around the drip line of my plants—often called top dressing—and then dig it into the existing soil a bit so that it does not just wash away or mound up at the crown of the plant when you next water them,” she says. When it comes to frequency, Jewell explains that the requirements are different for every type of plant. “I tend to dress my perennials, like roses and salvias, once in spring and once in fall with compost. I top dress my potted plants two times per year, once in spring and once midsummer, with fresh compost from my pile. And of course, I dress my summer vegetables every few weeks in their peak growing season,” Jewell explains.
The benefits of composting
In addition to saving wasted food and enriching your soil, one of the main benefits of composting is that you know exactly what went into your healthy soil, and therefore your plants and homegrown crops. Unlike store bought soil that runs the risk of exposure to chemicals or pesticides, homemade compost is cheaper, healthier, environmentally-friendly, and free of any plastic packaging.
“Compost mulch on your garden soil can help feed plants, deter weeds, keep roots cool in summer, and improve moisture retention in your soil, so you are using less water as well. It’s a win, win, win!” Jewell exclaims.