How Can I Re-use Coffee Grounds? - Uncle Jim's Worm Farm

How Can I Re-use Coffee Grounds?

Compost, Live Worms

coffee groundsWhile dumping coffee grounds into the trash, you might wonder, “Can I re-use coffee grounds?” Fancy coffee blends and pods are expensive. Is there a way to brew an additional cup or pot from used coffee grounds? Where should you put used coffee grounds? If you can’t re-use them, can someone or something else use them?

The Economics of Coffee Grounds

Coffee brewed at home has become increasingly diverse. In the past, only a few factors distinguished one coffee from another. Roast and brand name were the main attributes setting ground coffee or coffee beans apart. However, in the past 25 years, Americans have become fussier about their coffee. Is it organic? Fairtrade? Where was it grown? What is the strength? The acidity? Flavored? The coffee aisle at the grocery store has a dizzying array of choices. Specialty coffees from the health food store, coffee and tea boutiques, online mail order, and coffee shop chains mean even more selection.

The more characteristics, the more expensive. For example, ground ethical coffee runs around $15-$25 per 12 oz – 16 oz.[1] On the other hand, the extra cost helps support communities and bring farmers out of poverty.

Using a single-serving coffee pod is more expensive than brewing a pot. A 25.6-ounce canister of Maxwell House French Roast Ground Coffee makes 210 cups of coffee and costs $7, or 3 cents per serving. A 12-pack of the same coffee in pods costs around $8, or 65 cents per serving.

Is there a way to get more value from coffee grounds?

Re-Using Coffee Grounds

First Cup of Coffee

Can you re-use coffee grounds to brew another cup or pot of coffee? The test kitchens at Uncle Jim’s Worm Farm gave it a try. We used coffee grounds in a single-serving reusable basket.

The first cup was dark and delicious.

We ran water through the coffee grounds again. What came out might technically qualify as a coffee-like substance. It was dark and warm. However, this brew’s flavor was weak and watered-down. Coffee from re-used grounds contains much less caffeine. The coffee beans only have a set amount of solids, oils, flavor compounds, and caffeine. The first cup extracts most of these substances. We tipped the second cup down the sink.

So if we can’t re-use coffee grounds to make more coffee, can we still extract some goodness? We can’t, but composting worms can! Red worms turn trash into treasure: valuable fertilizer for your plants.

Composting Coffee Grounds

Second Cup of Coffee from Re-Used Grounds (Weak)

Coffee grounds are a favorite food for composting worms. Just set up a composting bin using a tote, a composting bin from the hardware store, or a convenient tray-based composter. Order composting worms from Uncle Jim’s Worm Farm. We recommend Red Worms for composting.

The worms have a voracious appetite for organic matter. They will eat through coffee grounds, potato peelings, kitchen scraps, left-over vegetables and fruits, and uneaten oatmeal. Worms will then excrete a substance called “humus”. This worm poop is one of the best all-natural fertilizers on the planet. After a few months, you can harvest the worm humus and dig the black excrement into the soil. Your plants will grow strong, and you will get more value out of your coffee grounds.

A Tip for Composting Coffee Grounds

Coffee grounds alone are a bit too acidic for the worms. Crushed eggshells act as a buffer. The worms will use the eggshells as “grit” to help grind up food inside their bodies. To add eggshells and coffee grounds:

  1. Whenever you crack an egg, rinse the shell. Set aside to dry.
  2. Save coffee grounds separately, or throw them in your compost collection container.
  3. When the eggshells are dry, and you have accumulated a pile of them, crush them using a rolling pin.
  4. Mix a handful of crushed eggshells in with the coffee grounds before or while feeding them to your worms.

You can learn more about setting up a composter on our website. Uncle Jim’s Worm Farm is the #1 supplier of composting worms in the United States. Check out our live worms, composters, and supplies.



[1] “How Much Should You Pay For Coffee Beans?” JavaPresse

7 thoughts on “How Can I Re-use Coffee Grounds?

  1. I save eggshells, and have had really good luck with smashing them or taking a rolling pin to break them up and then putting them in my nutribullet or food processor to further break them up. The nurtribullet turns them into almost a powder, and the worms seemed to love them. The food processor doesn’t grind them nearly as fine as the nutribullet, but I use what’s handy. Hoping to get my worm farm up and running soon.

  2. Is it necessary to “treat” eggshells by boiling or by microwave in order to kill any bad microbes prior to crushing or grinding?

  3. How do I get rid of small ants in my composting plastic bin placed outside without killing my worms.

  4. James, re:ants in your worm bin: Diatomaceous Earth DE) can be purchased on line or at most garden stores. It will kill the ants wiithout harming your worms. Just apply with a duster to the surface of your bin between mistings. It loses its value when wet.

  5. Diatomaceous. Earth can be put in feed for any livestock, at no more than 2% by weight. It will prevent flies from breeding in the animal’s feces.

  6. Ones I ask about coffee grounds and the answer was that soil will be to acidic .
    I decide to spread it under the citrus tree and roses but my warms like the filters .
    ( Avocado tree like more alkaline soil )
    My warms witch I ordered last Year like a lot avocado shells with some pulp in it .
    They hatch a lot on it like poppy seeds what make me very happy .
    .They like a lot of pineapple scraps .I have to much remnants so I decided order more warms .
    Thank You for information about ants spray and the egg shell preparation to composted .

  7. I read an article about research done at a university in Australia where coffee grounds in varying proportions were integrated into the soil medium in which plants were growing. In all cases, the plants grown in soil containing coffee grounds did more poorly than those grown without any coffee grounds. The more coffee grounds in the growing medium, the worse the plants performed. The explanation given was that caffeine is a chemical designed to protect plants in which it exists , hence a level of chemical toxicity, and thus acts as an inhibitor to plant growth unless it has first been composted, processed so that the caffeine is reduced/removed. Unfortunately, I could not find the article in which I read this so what i write is from memory of the article.

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