Dear Dot: Can I compost coffee and tea?



Dot tackles your thorniest questions from a perch on her porch.

Dear Dot,

Someone told me that used coffee grounds are really good for my backyard compost. Is that true? Where can I get some?

–Tea Drinker, Tisbury

Dear Tea Drinker,

I am the proud owner of no less than four composters: three outdoors that I use in warmer weather for food scraps and yard waste, and an indoor vermicomposter (the Latin vermis = worm) that exists in my basement year-round devouring my food scraps, tea bags, and coffee grounds with an efficiency that would make the Swedish blush. Composting delights me, as does your question.

It feels like magic — you dump in your banana peels, your carrot peelings, your soggy, blackened lettuce that was part of your I-really-mean-it-this-time plan to eat more salads, and, yes please, your used coffee grounds — and it becomes nutrient-rich fertilizer for your plants.

Adding coffee grounds to your compost is particularly good on the Vineyard, because our soil is acidic, says Roxanne Kapitan, a 30-year composting veteran and manager of Oak Leaf Landscape in West Tisbury. “Good for growing blueberries,” she says. “Not so good for vegetables.” She explains that adding coffee grounds creates a pH of 6.5 to 6.8. “Almost all vegetable plants need that exact pH level.” Of course, I say, pretending to know what pH is.

Adding coffee grounds to your compost is particularly good on the Vineyard, because our soil is acidic.

Coffee grounds, which are considered “green” in compost parlance despite their actual color, neutralize or alkilize soil, and also accelerate decomposition. If your compost pile has just carbon (considered “brown,” and including twigs, leaves, even coffee filters, compostable coffee cups, or the newspaper you read with your coffee), it won’t heat up effectively. These are some magic beans: If your soil is sandy, coffee grinds will help it hold water. If your soil is more claylike, they will break it down so it doesn’t hold so much water. 

You might be able to convince your neighbors to save their coffee grounds for you. Mocha Mott’s takes its grounds to IGI, but also gives them out to composting customers, but please bring your own containers, and call or check in first so they can show you the ropes the first time. Espresso Love in Edgartown also offers up used grounds, but supply is first come, first served. And, again, check in first.

One more thing, Tea Drinker. As long as the tea bag itself is not made of synthetic materials, it can be composted. A blogger who goes by The Wild Minimalist has a comprehensive list of which popular US teas come in compostable tea bags. Or play it safe and open the bags, adding just the tea leaves to your compost.

Love, Dot

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