Composting With Coffee Grounds: Everything You Need To Know!

Composting With Coffee Grounds: Everything You Need To Know!

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If you are one of the 150 million Americans who start their day with a fresh cup of coffee, you might be feeling a little guilty about tossing the old coffee grounds in the trash. The good news is you can put your old coffee grounds to good use right in your own yard and garden.

Coffee grounds are an excellent source of organic matter that can be put to good use in your garden. Not only can you compost coffee grounds, but you can also add them directly to the soil to enrich the soil and deter garden pests, too. But there are some things you should know about using coffee grounds in the garden.

How to Add Coffee Grounds to Your Compost

Adding coffee grounds to your compost doesn't require a lot of work or effort. But, you should be aware that because coffee grounds are high in nitrogen, they are considered green material in your compost pile. That means you need to mix your spent coffee grounds with other carbon-rich (brown) materials like dried leaves or shredded paper.

How you use coffee grounds in your compost depends on the number of coffee grounds you are using. If you simply want to put the spent coffee grounds from your morning coffee to good use, you can sprinkle them into the compost bin or compost tumbler and mix them in with your existing compost.

However, if you have an ample supply of coffee grounds to dispose of, you must use care to add them in the right proportions. Composting requires a 30:1 mix of carbon (brown) material to nitrogen (green) material by weight, says Cornell University. This ratio ensures there is enough nitrogen in the mix to decompose properly. Too much nitrogen can cause the release of ammonium gas and cause foul odors, while too little nitrogen will slow down the decomposition process.

Cornell lists coffee grounds with nitrogen to carbon ratio of 20:1, which means they must be mixed with plenty of brown materials to keep your compost pile healthy and active. Keep in mind these ratios refer to the weight and not the volume of organic materials. Many gardeners are successful with adding approximately equal amounts of green and brown materials (by volume) to the compost pile.

Use the health of the compost pile as your guide to determining if you need to add more brown materials to offset the addition of coffee grounds.

Signs Your Compost Needs More Carbon (Brown) Materials

Adding too many coffee grounds and not enough brown materials to the compost pile can lead to several issues. Watch for these signs that you need to add more brown materials, like dried leaves or shredded paper, to your compost pile.


Too much nitrogen-rich materials, like coffee grounds and fresh kitchen wastes, can cause the compost pile to overheat. This can kill off beneficial microbes and insects, too. Adding more dry materials and mixing them well will correct overheating issues.

Smells Like Rotten Eggs

Too many coffee grounds (and not enough brown materials) can cause your compost pile to smell like rotten eggs, especially when you turn it. Use this as a sign to add more brown materials to your compost, and make sure to turn it well.

Smells Like Ammonia

Too many coffee grounds (or other high nitrogen materials) can also cause your pile to smell like ammonia as it releases ammonia gases. To eliminate offensive ammonia smells and improve your compost, add more dry materials to the mix.

Looks Slimy

The pile may look and feel slimy if it does not have enough carbon materials to offset the nitrogen matter. For example, too many coffee grounds and other green materials and not enough brown matter to offset them may make your compost slimy. To correct the problem, mix in more dry materials like shredded paper or dried leaves and yard wastes and mix it in well.

Signs Your Compost Needs More Nitrogen (Green) Materials

Too many dry or brown materials in your compost pile can cause serious issues too. Watch for these signs you are adding too many brown materials and not enough green compost material, like coffee grounds and vegetable scraps.

The Compost Pile Isn't Heating Up

Your compost pile needs plenty of nitrogen-rich materials, like coffee grounds and kitchen wastes, to do its magic. The pile will not heat up and decompose without enough green compost material. If it fails to heat up properly, add more coffee grounds or other green materials to the compost pile.

The Compost Pile Isn't Decomposing

If the material in your compost isn't decomposing as it should, the most likely cause is insufficient green materials, like kitchen wastes and coffee grounds. So add more green material to the pile and mix it to boost the decomposition process.

The Pile Bursts into Flames

Although rare, your compost pile can heat up and burst into flames if it has too many carbon-rich materials and not enough nitrogen-rich materials. To prevent your compost pile from catching on fire, make sure to add green material frequently and mix it in with the existing material.

Click Here to Know What is the Green and Brown Material of Compost

How to Compost Coffee Grounds

Composting with coffee grounds doesn't require any additional composting supplies or any special techniques. They will compost just fine on their own, but you will need a good supply of coffee grounds and carbon-rich materials, like dried leaves, shredded paper, and yard wastes, too.

Remember, even though coffee grounds appear brown and dry, they are high in nitrogen content and must be considered green for the purpose of composting. Follow your regular composting routine, adding coffee grounds with fruit and veggie scraps, grass clippings, and other green composting materials.

Can you Compost Fresh Coffee Grounds?

You can compost both used and fresh coffee grounds, but unless you have a secret stash of fresh coffee grounds that you don't intend to brew into your morning coffee, there are better ways to use fresh coffee grounds than tossing them in the compost pile.

However, there is no need to throw away that half a can of stale unbrewed coffee grounds. They can be added to the compost pile without problems.

Can You Compost Paper Coffee Filters?

Paper coffee filters can be composted in the compost pile but should be shredded or torn into strips to speed the composting process. While organic coffee filters are the best, ordinary white filters can be composted, too.

Some coffee filters have been bleached and may add a small amount of bleach to the compost bin. If you are concerned about composting bleached filters, buy organic filters for your coffee.

Some coffee filters may be slow to break down, but as long as they are biodegradable, you can add coffee filters to the compost pile.

Click Here to Know More about Compost Coffee Filter.

Can You Compost K Cups?

The used grounds and paper liner of K cups can be composted, but you will need to open and separate them from the plastic cup before using them for making compost. You can purchase cutters made specifically for separating the K cup from the paper liner and coffee grounds, but it can be done with a sharp knife or kitchen scissors with a bit of effort.

Cut the top of the K cup away from the plastic cup. Discard the top in the trash. Next, run a sharp knife around the inside rim of the K cup to cut the filter from the plastic cup. Place the coffee grounds and paper filter in a bowl or container and toss them in the compost pile when you are ready.

Some companies now produce K cups made from plant-based materials that are fully compostable. These compostable K cups do not need to be opened or separated before adding them to the composter.

How Long does It Take Coffee Grounds to Compost?

Composting coffee grounds doesn't take any longer than composting other kitchen and yard wastes. When composted in an outdoor compost pile and turned once a week, the coffee grounds will turn to usable compost within three to six months.

Kitchen composters or compost tumblers may produce compost quicker, depending on the design of the composter. For example, the Karfo kitchen waste composer can transform coffee grounds and other kitchen scraps into usable compost overnight. Check with your user's manual to determine the amount of time it will take to turn coffee grounds and kitchen wastes into usable compost in your particular type of composter.

How to Use Fresh Coffee Grounds in the Garden

Fresh coffee grounds can be beneficial in the garden, too. Consider these uses for fresh coffee grounds in the garden.

Use Fresh Coffee Grounds for Acid Loving Plants

Unlike used coffee grounds that have a fairly neutral pH, fresh, unwashed coffee grounds are acidic. Therefore, they can be used to raise soil's acidity levels for acid-loving plants.

Simply sprinkle fresh coffee grounds around acid-loving plants like blueberries, lilies, azaleas, and hydrangeas and work them into the soil. Avoid fresh coffee grounds near tomatoes.

Use Fresh Coffee Grounds to Deter Pests

The caffeine in fresh coffee grounds is thought to be an effective deterrent for slugs, snails, rabbits, and cats when sprinkled around the base of plants. They may deter other garden pests, too. Work the unbrewed coffee grounds into the top inch or two of the existing soil. Coffee grounds spread on top of the soil will dry out and prevent water from entering the soil.

Use Fresh Coffee Grounds to Suppress Weeds

Unbrewed coffee grounds also help to suppress weeds and can be sprinkled around plants to help control the growth of weeds. Mix coffee grounds into the top few inches of the soil. But beware. Tomato plants do not like coffee grounds. So do not add coffee grounds near your tomato plants.

Used Coffee Grounds Are Not Acidic

Contrary to common belief, used coffee grounds are not acidic and don't pose a risk of altering the soil pH. While unbrewed coffee grounds are acidic, the acid in coffee grounds leaches into the water when you brew your coffee, leaving the spent coffee grounds with a pH of 6.5 to 6.8 and are close to neutral pH, says Oregon State University.

How do Coffee Grounds Improve the Soil?

Coffee grounds make an excellent soil amendment that improves the soil in several ways. Using coffee grounds to add organic matter to the soil is a safe and effective way to improve the soil. Check out these amazing benefits of adding coffee grounds to your garden's soil.

Coffee Grounds Add Organic Matter to the Soil

When you add coffee grounds to your garden soil, you add valuable organic matter that your plants need to thrive. Organic matter enriches the soil and provides a good source of slow-release nutrients to your plants.

Coffee Grounds Improve Aeration

Adding coffee grounds to the soil helps keep the soil aerated by creating tiny air pockets. Air pockets in the soil make it easy for young roots to grow and access the water and nutrients in the soil. It also provides roots with the oxygen they need for healthy growth.

Coffee Grounds Improve Drainage

Plants need well-draining soil to prevent the soil from getting soggy and choking out oxygen to the roots. Adding coffee grounds to the soil improves drainage and helps your plants get the oxygen they need. They also prevent the soil from compacting or forming a crusty surface.

Coffee Grounds Attract Earthworms

Worms love coffee grounds, and that's good news for gardeners. Earthworms burrow through the soil, improving aeration and water filtration. They also add organic matter with their castings. They prevent the soil from becoming compacted and make nutrients available to the plant's roots. Add coffee grounds to your soil to attract earthworms and reap the benefits they provide for your garden.

Coffee Grounds Add Nitrogen to the Soil

Many gardeners report using coffee grounds as nitrogen fertilizer. Still, the Oregon State University Extension (OSU) explains that although coffee grounds are an excellent source of nitrogen in the compost pile, they are not a nitrogen fertilizer when applied directly to the soil without composting them first.

OSU recommends adding extra nitrogen fertilizer to the soil at the same time you add uncomposted coffee grounds to the soil. The coffee grounds and the nitrogen fertilizer work together to improve the soil. In addition, the coffee grounds encourage the growth of microorganisms that need nitrogen to grow and reproduce.

As the coffee grounds in the soil decompose and break down, they then release more nitrogen into the soil. Nitrogen is vital to plant growth and promotes healthy stems and foliage.

Coffee Grounds Add Phosphorus to the Soil

All plants need phosphorus to grow. It helps plants build strong root systems to transport water and other nutrients and to provide support for the plant. Phosphorus is also needed for the plant to carry out photosynthesis and make and store energy from the rays of the sun. Phosphorus is vital to plants maturing and producing healthy fruits.

Coffee grounds provide a good source of phosphorus to the soil.

Coffee Grounds Add Potassium to the Soil

Potassium is essential for healthy plant growth. It helps plants use water effectively and helps combat the effects of drought. In addition, it promotes healthy fruit development by regulating plant growth.

Adding coffee grounds to the garden adds the vital nutrient potassium to the soil.

Click Here to Know More about the Living Soil

Can You Use Coffee Grounds for Mulch?

Coffee grounds can be used for mulch in the garden if you cover them with leaves, hay, or other organic matter. When placed on top of the soil, coffee grounds dry out quickly and form a crusty layer on top of the soil. In addition, dried coffee grounds on top of the soil will cause water to run off when it rains, preventing water from entering the soil.

When coffee grounds are used under other organic mulch, they help to retain moisture and suppress weeds. If you have a surplus of coffee grounds, try using them as the base for mulch around your flowers and vegetables.

Where Can You Get Coffee Grounds?

If you are looking for a good source of coffee grounds for composting, you may be surprised to discover there may be several sources for free coffee grounds right in your own neighborhood. Coffee shops, restaurants, and other food establishments often have hoards of coffee grounds at the end of the day and have to pay to have them hauled away to the transfer station or landfill.

Most will gladly save them for you as long as you pick them up in a timely fashion. Take a drive around your neighborhood and look for businesses that regularly serve coffee. This includes convenience stores, the local coffee shop, and even hospital cafeterias. Check with your local coffee house to find out what you need to do to get their used coffee grounds for composting.

You may need to provide a bucket or bin for collecting the spent coffee grounds and agree to pick them up regularly. You can buy a 5-gallon bucket at the local hardware store for a few dollars, which is money well spent in return for coffee grounds for your garden and compost.

How is Composting Coffee Grounds Good for the Environment?

According to Bio-Bean, an astounding 9 million tons of coffee is brewed worldwide each year. That produces 18 million tons of spent coffee grounds. It is estimated that 75 percent of those coffee grounds end up in landfills where they get trapped and cannot decompose efficiently.

Coffee grounds in landfills do decompose eventually, but without the oxygen they need, they cannot decompose aerobically like they do in a compost pile. So instead, these coffee grounds are subject to anaerobic decomposition and give off large amounts of methane. Methane is a greenhouse gas that is 25 times more powerful than carbon dioxide when contributing to global warming.

Preventing coffee grounds from landing in landfills is a big step towards reducing global warming. When you turn them into usable compost, you help build rich soil in your own garden. Collecting and composting coffee grounds from the coffee shop or other food establishments helps the environment and reduces your carbon footprint, too.

Do Used Coffee Grounds Contain Caffeine?

Most of the caffeine in coffee beans is lost during brewing as the caffeine seeps into the hot water giving you the morning jolt you desire. However, some traces of caffeine remain in the old coffee grounds and can add traces of caffeine to the soil. The small amount of caffeine in the used grounds does not pose a danger to your soil.

Can You Use Leftover Coffee in the Garden?

Some people report using leftover coffee to water plants in the garden. It may be beneficial around acid-loving plants as brewed coffee is acidic. Although it isn't recommended that you pour gallons of cold-brewed coffee around your plants, a cup or two of leftover coffee on occasion isn't likely to hurt your plants and may even be beneficial.

Do Coffee Grounds Inhibit Germination?

Adding coffee grounds directly to the soil without composting them first may cause problems with seed germination. A study conducted on lettuce seeds planted in soil with 25 percent uncomposted coffee grounds showed delayed or reduced germination rates.

If you choose to add used coffee grounds directly to the soil, it is best to do so after your seedlings have emerged or later in the summer so the coffee grounds will have time to break down in the soil before planting time in the spring.

Composted coffee grounds do not affect the germination rate of seeds.

Can You Use Flavored Coffee Grounds in Compost?

If you enjoy flavored coffee and customarily brew a pot of delicious hazelnut or vanilla flavored coffee, you may wonder if it is okay to add coffee grounds from flavored coffee to the composter. While there is little information on the topic, many gardeners claim they toss both flavored and unflavored coffee grounds into the compost pile without experiencing issues.

Because the flavoring in flavored coffee is made from natural ingredients and likely dissolves in the water when you brew your coffee, it is unlikely that traces of flavoring left in the used coffee grounds will have any effect on your compost.

How Should You Store Used Coffee Grounds for Composting?

Used coffee grounds can be stored in a bowl or bucket for several days before adding them to the compost pile without getting smelly, as long as you don't add other kitchen wastes to the container. Consider a large resealable container under the sink or on the counter for collecting and storing your used coffee grounds until you are ready to take them out to the composter.

Composting with coffee grounds is a great way to reduce your contribution to landfills while improving the condition of your garden soil, too. Whether you choose to compost on a small scale with the grounds from the morning pot of coffee or seek out large amounts of coffee grounds from local food establishments is up to you. Both will provide you with valuable organic matter to enrich your soil and help reduce the demand for landfills.


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