According to the International Coffee Organization, people consumed more than 166,000 bags of coffee (weighing 60 kilograms [kg] each) worldwide in 2020–2021. The United States accounted for over 30,000 of these bags.
Coffee grounds can be useful in several ways. The sections below look at some of these in more detail.
Skin exfoliation product 
People can mix coffee grounds with water, honey, or coconut oil to create a skin scrub that they can use all over the body.
Exfoliation removes dead cells from the top layer of the skin and can unclog pores, clean the skin, and reduce acne. It may also make the skin look brighter and reduce the appearance of fine lines.
One 2013 study suggests that caffeic acid, an antioxidant present in coffee, may reduce premature cell aging and boost collagen levels.
Natural dye
Coffee has a strong color, and coffee grounds can dye natural fabrics to different shades of tan and brown.
One 2019 study found that coffee grounds are a potential natural dye for use on a commercial scale, as the fabrics the researchers dyed in the study stayed colorfast to industry standards.
People can also use coffee grounds to dye their hair, though they may not produce a significant color change or last for a long time. That said, they may be suitable for a short-term change.
According to the American Cancer Society, research has not been able to confirm whether or not commercial hair dyes cause cancer. However, some chemicals present in some hair dye products may have the potential to cause cancer.
Fertilizer
Plants need nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur to grow. Coffee grounds can conserve the nitrogen content of soil, which may benefit plant growth.
One 2019 study found that mixing coffee grounds into soil improved the nutritional value of lettuce.
However, a 2016 study found that coffee grounds slowed down plant growth but retained moisture in the soil and reduced weeds. This study also suggested that more research is necessary to confirm the benefits of using coffee grounds as fertilizer.
Insect repellent
Coffee contains diterpenes, which
One 2018 study concluded that although coffee grounds were not toxic to ants, it was an effective repellent against them.
Coffee may also be an effective method of mosquito control, as a 2015 study found that mosquitoes were less likely to hatch if coffee was present in their environment.
Flea repellent
Fleas also do not like coffee grounds. Because of this, a person might be able to try rubbing coffee grounds into their pet’s fur if they have fleas.
However, before doing so, they should check with a vet to make sure that this method of flea prevention is suitable for their pet.
Caffeine is toxic to cats and dogs, so people should be careful not to let their pet eat coffee grounds. Caffeine poisoning can cause symptoms within around 30 minutes and be fatal.
Cleaning product
Coffee grounds are a coarse powder. This means that they are abrasive and that people can use them to scrub surfaces, utensils, or appliances that have ingrained or hard-to-remove dirt.
That said, coffee grounds may be too rough to use on delicate surfaces or utensils.
Odor reliever
The caffeine in carbonized coffee grounds can eliminate odors by absorbing hydrogen sulfide molecules from the air.
As a result, people can make coffee grounds into soaps to neutralize odors on the hands after cooking, for example, or to minimize odors in shoes.
Meat tenderizer
Meat tenderizers use enzymes to break down fibers in meat to make it softer and easier to eat. Meat tenderizing powders use acids and enzymes from fruits such as pineapple and papaya.
Coffee grounds are acidic and contain enzymes that can also break down fibers in meat, so a person can try using coffee grounds to soften meat before cooking it.
A person can also marinate the meat in coffee or use coffee grounds as a meat rub to add flavor. 
Furniture restoration product
A person can also use the strong color of coffee to restore scratched wooden furniture.
After mixing coffee grounds with water, a person can rub the resulting paste into scratches on wooden furniture to match the original color.
More uses of coffee grounds
What are some other things you can think of to use coffee grounds? Let us know.