In 2013, a Welsh IT engineer named James Howells got a new laptop and threw away his old one. That story wouldn’t have made headlines (and I wouldn’t be sharing it here) except for the fact that the hard drive of the trashed computer contained 7,500 Bitcoins, at the time worth roughly $250 million. When he discovered his calamitous mistake, he offered the Newport City Council over $75 million to dig up their landfill until they found the hard drive. They refused, citing logistical and environmental obstacles.
While most of us will never throw away anything quite so valuable, we can still unknowingly toss stuff that can still be of great use. For example, many people toss another common (and less valuable) substance on a daily basis that could be serving a multitude of purposes.
I’m referring, of course, to coffee grounds.
Coffee Grounds Are Valuable
Coffee is one of the world’s most popular beverages, with an estimated two and a quarter billion cups consumed worldwide each day. And because of how coffee is made, that results in an awful lot of unconsumed by-products. Every year, humans collectively generate an estimated 23 million tons of spent coffee beans. For funsies, that’s about the weight of 470 fully equipped Cunard Line QE2 ocean liners.
But here’s the thing: While these coffee grounds may be “spent” in terms of making a quality cup of joe, they’re far from spent in terms of chemical, nutritional, and thermodynamic value. And many people are starting to catch on to the unrecognized value of coffee grounds.
Already, aspiring social entrepreneurs are innovating industrial reuses of coffee grounds, from inventing ways to process coffee grounds into fireplace logs and pellets, turning them into flavor additives, and even utilizing them to replace synthetic materials in manufacturing.
Coffee shops often have programs to collect bulk amounts of used grounds and share them with local nurseries, farms, and home gardeners (and you’ll see why in a bit!).
But you don’t have to wait for science or industry or commerce to figure out how to reuse coffee grounds. If you or anyone in your home is a regular drinker, spent coffee grounds no longer have to be a wasteful part of the morning routine. Instead, you can reuse them in elegant and clever ways. Not only will you reduce your ecological footprint, but you’ll also add value to other parts of your home and life.
Why Consider Saving Coffee Grounds
Let’s look at what happens to coffee grounds that end up in your kitchen trash. Much of the wet, pulverized remains of roasted coffee beans are sent to the landfill, where they emit methane gas and contribute to global climate chaos. If you send them packing via your garbage disposal, they can build up in your pipes (the disposal won’t grind them any finer than they’ve already been ground) and may eventually lead to a blockage.
And even if these disposal methods were benign, rather than harmful, spent coffee grounds contain enough residual value to warrant giving them a second life.
Coffee grounds can retain up to one-third of their original aromatic and beneficial compounds (including antioxidants) as well as oils and even the controversial but widely coveted caffeine. They also generate a surprisingly high energy output (which is why they make a great sustainable alternative to wood-based fuels like pellets and fireplace logs). And for the gardeners out there, coffee grounds are a rich microbial food source for beneficial organisms — the little critters that do the crucial work of keeping your soil bountiful and fluffy.
We can collectively reduce how many tons of coffee grounds we send to landfills or down the drain by innovating new ways to reuse or “upcycle” grounds. And many of these ways are simple, low-tech, and easy to implement on a personal scale. By reusing and/or upcycling the coffee grounds you (or your household) produce, you can reduce your environmental impact while also improving your life.
How to Reuse Coffee Grounds
1. Add Coffee Grounds to Soil
One of the twelve principles of permaculture (a sustainable and regenerative approach to farming and gardening) is to use and value renewables. And just as cardboard and fallen leaves can break down and return carbon to your soil, so too can coffee grounds share their residual nutrients with your garden beds.
If you’ve been gardening in the same spot for a while, everything you harvest represents some depletion of soil nutrients and minerals. You can spend money to replenish them with amendments harvested and processed from some other piece of land, or use synthetic fertilizers, but why not keep the nutrient cycle local and use coffee grounds to help restore fertility?
Coffee contains key minerals for plant growth, including nitrogen, calcium, potassium, iron, phosphorus, magnesium, and chromium.
To amend soil or garden beds with coffee grounds, here’s a simple 3-step plan:
- Sprinkle a ½-inch layer of grounds on the area you want to amend.
- Lightly till or scratch into the soil.
- Water as needed.
The grounds will slowly release nitrogen and feed beneficial soil microbes as they break down. One reason to gently till the grounds rather than just tossing them on the surface is that they will repel water when left on top of the bed. Gently incorporated into the soil substrate, they’ll help retain moisture and preclude the need for frequent watering during dry spells.
As an added bonus, the grounds may help deter pests that annoy your plants (like slugs) and annoy you (like mosquitoes).
2. Fertilize Houseplants with Coffee Grounds
Like garden crops, houseplants can also benefit from coffee grounds fertilizer, with one small but significant difference. While you want most garden beds to retain moisture, the roots of your potted plants can become oversaturated with water if you add grounds directly to the soil. A better way to get coffee nutrients working for your houseplants is to turn the grounds into a liquid fertilizer “tea.”
Make the tea by steeping up to one cup of used grounds in a gallon of water for a few hours or overnight. Then strain out the grounds using a sieve, a cheesecloth, or (who’d ever think of this?) a coffee filter, and use the remaining “tea” as a liquid fertilizer. You can pour it into the soil, or put it in a spray bottle and use it as a spray directly on the leaves.
But wait, there’s more! You can reuse the strained grounds on garden beds, or in compost piles because even after all that, they still have some nutritional love to give to your soil.
Both the tea and the twice-used grounds can provide supplemental nitrogen to your plants, and since they’re relatively pH-neutral, you don’t have to worry about acidifying your potting soil. And because plants lack central nervous systems, it’s unlikely that cold brew will make them jittery.
3. Compost Coffee Grounds
As we’ve seen, coffee grounds are rich in nitrogen, calcium, and potassium — all of which are essential building blocks of rich compost. And compost is any gardener or farmer’s best friend since this highly fertile material can rejuvenate your soil, helping produce bigger, tastier, and more nutritious yields. Adding healthy compost to your garden allows your beds to retain more nutrients and water, buffering them against both nutrient depletion and drought.
We make compost by fostering the natural decomposition of organic matter, like food scraps and yard debris, along with providing sufficient water and oxygen. And coffee grounds are one of the best food scraps to add.
First, they can help compost smell better; most people prefer the aroma of a dry roast to that of rotting squash peels. Second, compost that includes coffee grounds is higher in nutrients than coffee-free compost. A 2009 study compared three formulas used in vermiculture, a form of composting that employs worms to eat the waste and convert it into soil. While the worms appeared to enjoy cow dung and kitchen scraps, their favorite meal was cow dung mixed with coffee grounds, as measured by how much they grew and multiplied.
If you don’t have access to a source of cow dung (which, according to my research, is generally a cow), or you prefer vegan gardening, without any animal inputs, then you can follow the formula recommended by Oregon State University: equal parts coffee grounds, dried leaves, and fresh grass clippings.
4. Create Baked Goods and Other Tasty Treats with Coffee Grounds
Have you ever been disappointed when you took a bite of coffee cake to discover it didn’t actually taste like coffee? Talk about false advertising!
Luckily, if you love the taste of coffee enough to want to add it to baked goods, you can upcycle coffee grounds in a variety of baked goods and desserts. Typically, you want to use more finely ground coffee for this purpose.
Ways to use coffee grounds in baking:
- mix them into cake, brownie, and pancake batter
- add them to bread and cookie dough
- stir them into savory rubs for vegetables and tofu
While I wouldn’t eat them by the spoonful, coffee grounds are safe to consume in small amounts. And bonus, they also contain antioxidants and dietary fiber!
Just remember that they also contain caffeine, so unless you want to spend the night sitting up in bed alternating between wondering what that sound was and where you put the receipt for that thing you need to return, you probably don’t want to eat coffee-infused baked goods after dinner. (If you perform shift work, do whatever you need to do to that last sentence to make it work for you.) Of course, decaffeinated coffee grounds contain little to no caffeine.
5. Clean Stubborn Dishes with Coffee Grounds
No, I’m not talking about the Pyrex casserole that refuses to fit into your toaster oven no matter how nicely you ask. By stubborn, I’m referring to dishes with hard-to-clean, baked-on food and stains. Turns out that coffee grounds can serve as a great natural cleaning scrub for nonporous surfaces.
They may even have a sanitizing effect due to their antiviral and antibacterial properties. (These properties are so intense, researchers have begun using leachate from coffee to disrupt the life cycle of Aedes albopictus, the mosquito that transmits dengue fever. That’s especially good news because the little buggers have recently started to develop immunity to some pesticides.)
Even if you’re not trying to prevent the spread of tropical diseases, you can still take advantage of coffee’s cleaning powers. Keep coffee grounds on hand in the kitchen to scour the sink, polish your cookware, and clean your stove. Just make sure to avoid porous surfaces such as the grout between tiles, as the grounds can stain them brown.
6. Kitchen Odor Removal with Coffee Grounds
Coffee grounds don’t just leave surfaces looking cleaner; they can help your spaces smell cleaner as well since they’re great at absorbing and neutralizing odors. When combined with carbon, the nitrogen in coffee grounds can eliminate foul-smelling sulfur gasses from the air. (You can make this magic happen even if you did poorly in chemistry class.)
You can keep a bowl of coffee grounds in your fridge or freezer to help contain smells from spoiled or fragrant food. Or, dry out the grounds and add them to socks and pantyhose (ones you aren’t wearing, preferably) to create simple, portable, chemical-free air fresheners. Depending on how grotty the socks or hose are, they might make great DIY gifts — the ultimate stocking stuffer!
You can store used coffee grounds in a container next to your kitchen sink. Dip your fingers in the grounds and scrub with water to remove aromatic oils and fragrances from your hands after you’re done cooking.
7. Exfoliate with Coffee Grounds
Coffee grounds are a great natural exfoliant that can be easily added to coconut oil, moisturizers, or soaps. You can safely add a small amount of used grounds to a mixture that works for your skin type and massage it into your face and body. Not only will they help remove dead skin, but they also contribute antioxidants that can help protect your skin from sun damage. And vigorous scrubbing with coffee grounds can increase blood flow, leading to healthier, more vibrant skin.
8. Repair Scratches on Dark Wooden Furniture
OK, now we’re getting into “Crazy Plant-Based Hacker” territory. But yes, coffee grounds are a cheap and chemical-free alternative to dark-finish wood restorers.
Here’s how to conceal and buff out scratches on wood surfaces with coffee grounds:
- Apply wet grounds to the damaged area and gently rub in with either a cotton cloth or cotton swab for smaller areas.
- Wait 10 minutes.
- Remove the coffee grounds and excess moisture with a clean cloth.
9. Create a Natural Coffee Dye
If you’ve ever spilled coffee on a white rug or tablecloth, you may be well aware of its power to create stains that just won’t come out. While you may not appreciate this quality if the item in question was part of Grandma’s trousseau, you can put it to use on any items you’d like to turn brown on purpose.
Used coffee grounds show promising potential as a nontoxic replacement for commercial food, textile, and cosmetic dyes. And you can adapt these industrial processes for your own home. Coffee grounds can effectively color cotton, rayon, cellophane, linen, and paper.
One clever tip is to inexpensively refresh your stained tea towels with a coffee ground dye. Here’s the process:
- Rewet and boil your coffee grounds for 30+ minutes, adding water as necessary.
- Remove from heat and add the material you wish to dye (for some materials, you may need to let the water cool).
- Soak until the desired hue is reached. To achieve a light tan color, you only need a few minutes. For a darker brown, leave to soak for at least 30 minutes, or even overnight.
- Rinse and wash fabrics before mixing them with other garments.
10. Rid Your Companion Animal of Fleas
Most flea-removal products have harsh chemicals that can harm your dog or cat. And while fleas appear pretty easygoing when it comes to choosing their homes, they really don’t seem to like being around the compounds found in coffee. So do coffee grounds repel fleas?
Yes! Simply rub coffee grounds into your companion animal’s coat while shampooing, and then rinse. (If they retain a little mocha aroma and brown color, you may need to resist the urge to change their name to Starbucks or Cappuccino.) Coffee grounds act as a chemical-free flea deterrent. If this nontoxic, DIY flea treatment doesn’t do the trick, you may want to discuss other options with your vet.
Don’t Throw Away Spent Coffee!
The many uses for used coffee grounds make them worth recycling or even upcycling. If you or anyone in your home is a regular creator of coffee waste, now you’ve got a bunch of ways to keep them out of landfills while saving money. Plus, you can retire a bunch of synthetic chemicals in favor of a safe and nice-smelling alternative.
Tell us in the comments:
- Which way to reuse coffee grounds was most surprising to you?
- Have you ever used coffee grounds that were left over after making coffee?
- What’s one “coffee ground hack” you’d like to try?
Featured Image: iStock.com/CalypsoArt
