13 Surprising Uses For Coffee Grounds You Should Know About

Funky-smelling fridges are nothing new — it happens in the best kitchens. The good news is you can recycle one mess — wet, used coffee grounds — for this stinky situation. Because of the nitrogen found in coffee, the used grounds can actually help neutralize odors. As Science Daily explains it, coffee is caffeine-rich, as we know, and caffeine consists of nitrogen; nitrogen acts as a natural booster for carbon's process of adsorption, which is how carbon removes sulfur, a common cause responsible for noxious odors.

To use coffee grounds to eliminate the foul smell in your fridge, begin by drying them out, then put them in an open container and set them on the refrigerator shelf. Remember though, that natural odor eliminators such as coffee grounds or vinegar are already strong-smelling so by using them to get rid of foul smells, you're also inviting their scents to take over the fridge. 

Cooking with coffee isn't entirely new, but how about using coffee for the mess left behind? For an eco-friendly method to scrub away tough residue on your pots and pans, try using coffee grounds. Because of the naturally abrasive texture, they work well for scouring, especially cast iron skillets. You can use only the grounds, or you can mix a small amount of soapy water to make your scrub. If you're scouring cast iron, it might be best to forgo the soap unless you're facing something the rough grounds can't fight alone. But this trick won't work for every pot and pan — if it's ceramic, it may scratch the surface. Even though ceramic is tough, hard scrubbers like steel wool (or coffee scrubs) are known to cause damage.

While the texture plays a large role in how effective a coffee scrub is, the acid in coffee also lends a hand to the cleaning. According to Healthline, the beverage is quite acidic and the finer the grounds, the more acid a cup of brewed coffee might have. Keeping this in mind, if you use spent coffee grounds that are very small, the increased acid could help with cleaning even more.

You can bypass the hassle of messy powders by sprinkling fresh coffee grounds into your shoes as a natural and effective way to absorb odors. Shoes tend to get particularly miasmic because of the buildup of bacteria and moisture from sweat, which cause unpleasant odors that are persistent long after the sweat is gone. An experiment published in Towards Data Science shows that coffee grounds are capable of absorbing quite a bit of water, suggesting they'll efficiently get rid of the moisture in shoes, as well. Aside from the porous nature of coffee grounds that allows them to act like tiny sponges, coffee also contains nitrogen, an organic deodorizer.

This process won't work with wet or used coffee grounds like some of these other solutions; you'll want to ensure they're completely dry before you get to work. Fill a pair of socks or small sachets (or makeshift ones with nylon pantyhose or coffee filters) with the coffee grounds and place them inside your shoes overnight. Not only are you left with odor-free shoes, but you've done so in an environmentally-safe way without using harsh or unknown chemicals.

Whether used as a tenderizer, rub, or marinade, coffee's acidity and complex flavor profile can help elevate your meat recipes. As far as what kind of coffee to go with, it all depends on the roast. If you're a beginner to the wide world of coffee beans, it helps to know a few basics. Dark roasted coffee tends to have a more bitter flavor and less acidity, while a light roast is not only more acidic but it usually has more caffeine. While the caffeine content won't matter when marinating or tenderizing meat, acidity is vital. Acidic liquids or foods can help break down the connective tissue in meat, so using a highly acidic coffee will certainly work well as a tenderizer, especially in tough cuts of meat like brisket, chuck roast, or steak.

Coffee can also add a unique flavor when used as a rub or marinade. Combined with other complementary spices and herbs, coffee gives a rich, smoky, and slightly bitter taste. Coffee rubs are often applied to meats before cooking, which can form a delicious crust as it cooks on the grill or roasts in the oven. By using a coffee-based marinade or applying coffee directly as a rub, the meat's fibers start to soften too, leading to a more tender and flavorful outcome. While there are a plethora of coffee-infused recipes, we suggest trying coffee-rubbed steak or coffee pot roast.

To deep-clean various surfaces with an eco-friendly solution, try incorporating coffee grounds into your cleaning regimen. Not only are they gritty enough to face difficult dirt and grime, but they also have antibacterial properties that can aid in sanitization. When used with a sponge or cloth, they can help remove residue, especially on sinks, grill grates, and countertops. Just make sure to wipe them out of the sink instead of rinsing them down the drain because they could clog your pipes. Contrary to previous claims that running coffee grounds down the drain could break down grease in the same way it does on surfaces, coffee grounds are not water-soluble, so they can actually cause blockages.

Both caffeine and caffeic acid are present in coffee, and these natural substances can reduce harmful bacteria, creating an organic sanitizer. A study in Applied and Environmental Microbiology shows the positive effects of caffeic acid on bacteria (called "bactericidal activity") such as E. Coli and Salmonella. For best results, combine fresh coffee grounds — or make sure to hand-dry used ones — with dish soap and mix it together to create a paste that you can use to scrub down your kitchen counters and appliances.

Both burning coffee grounds as incense and sprinkling wet grounds in your garden are organic ways to help repel mosquitoes and other insects from your lawn. Between the strong smell, the color, and the components of coffee, it acts as a decent repellent. As explained by a study in Parasites & Vectors, coffee has qualities that are unattractive to mosquitoes and flies, plus caffeine can potentially inhibit a spider's capability to weave its web. Furthermore, it's possible for coffee to kill some unwanted insects and larvae. All of this aside, mosquitoes are also attracted to our sweat and the carbon dioxide we exhale, so this isn't a fool-proof method for the pesky biters.

Despite understanding that some mosquitoes might remain stubborn, we think it's worth a shot. Burning coffee grounds is fairly straightforward; just make sure to use a heat-resistant dish — like something metal or ceramic — to put the coffee grounds in before lighting them on fire. If you don't feel like playing with fire, you can spread damp coffee grounds around the base of plants or in areas where you want to repel insects.

Coffee grounds offer valuable benefits for your garden by helping to regulate soil acidity while also providing nutrients that act as fertilizer. When used in moderation, they can positively impact plant growth, but if you use too much, they could cause balding in your garden, courtesy of a caffeine overdose. According to some studies, caffeine has been shown to impede the growth of roots, so take care not to go overboard.

If used correctly, which requires sprinkling damp grounds only in the areas you want it to affect, the slight acidity of coffee grounds is ideal for acid-loving plants like tomatoes, begonias, rhododendrons, and azaleas, as they help maintain an optimal pH balance in the soil. Additionally, they are an excellent source of nitrogen, phosphorus, and potassium, all of which are considered fundamental macronutrients for promoting soil health. According to the University of Wyoming, they consist of "2% nitrogen, 0.06% phosphorus, and 0.6% potassium by volume." These nutrients gradually release into the soil as they decompose, acting as a slow-release organic fertilizer for various plants, especially nitrogen-demanding species such as corn, tomatoes, lettuce, spinach, and sunflowers.