Composting is becoming more and more popular among households. Everyone wants to try it out!

And why wouldn’t you? When you compost you lessen the amount of trash your family produces. This can reduce the cost of garbage pickup, result in a decrease of landfill usage, save money on trash bags, and even set you up with a free soil amendment!

A big concern is this: Does compost smell bad?

No, compost doesn’t smell bad. At least, not if it’s being processed properly. It should smell like fresh, rich dirt. If it doesn’t then something is going wrong. That’s why composting toilets are such a viable options for tiny homes and RVS (click here to learn how they work).

In this article we discuss reasons compost odor might appear and ways you can avoid it!

What is Compost?

Let’s make sure we’re all on the same page.

Compost is an amendment that is added to soil. It amends the soil with organic nutrients which are taken in by the root systems of plants. To make good compost, we use dry materials rich in carbon such as hay, dry leaves, paper, straw, and even cardboard. Also added are wet materials rich in nitrogen such as grass clippings, coffee grounds, fruit and vegetable scraps, and plant clippings.

The composting process just needs a balance of moisture and air, and then nature takes takes care of the rest. For bacteria, fungi, and worms, it’s an excellent food source. These creatures will break the soil down into micro-nutrients for other creatures and plants.

Why does compost smell?

Well, it shouldn’t.

If you smell a foul odor from a compost pile or bin, then there is something wrong. The balance of your compost is off, your compost may not be heating up correctly, or it may be failing to break down the organic matter. Here are some common reasons compost starts to smell, as well as some easy fixes.

The compost isn’t getting enough oxygen

If your compost pile isn’t aerated correctly, then the microorganisms and bacteria which break down the raw materials can’t do their jobs properly. Aerobic bacteria (the good bacteria) need oxygen to function. They help to break down the content in a compost bin. If there isn’t a healthy airflow and a healthy population of aerobic bacteria, then the anaerobic bacteria take over. This type of bacteria produce some disgusting odors during their metabolic processes. This is what makes the appalling smell, so keeping the balance in check is essential for a successful compost pile.

The first step to address this issue is examining compost location. If it’s in a shady, wet, or a damp area if so, this could cause improper air flow. Air has a rough time traveling through water.

Compacted compost can occur even without water. You may have too much dense material piled up which prevents oxygen from finding its way into the center of the compost pile. If your compost smells like rotten eggs, this is probably your issue.

If your compost is compacted, turn the pile over. If you’re using a tumbling compactor, just roll it or turn it over. If your compost is in a pile in the fresh air, then take a pitchfork or rake and turn everything over to expose the depth of the pile. This will give the pile some much needed fresh air circulating throughout. You can do this once a week until the compost smell is vanished then turn it over as whenever it’s needed.

Parameter Imbalance

The most successful compost piles are located outdoors with proper exposure to wind, rain, and sun. If any of these elements are off-balance then you’re going to have a problem. It inevitably creates stagnant compost.

You need to choose a spot for your compost pile that will receive at least 6-8 hours of direct sunlight. You also will need to turn the pile once a week (unless it’s being aerated another way). If it doesn’t rain at least once in a week, you may want to spray down the pile with a hose.

Composting doesn’t have to be a precise science. You don’t need to check moisture every 72 hours – just check on it when you are doing your other gardening tasks.

The Carbon:Nitrogen Ratio is Off

When you compost, keeping the greens and browns in balance is the primary goal. “Greens” are the nitrogen-rich material, and “Browns” are the carbon-rich material. The green-brown ratio can be anywhere from 50:50 to 20:80 depending on a variety of factors: different compost methods, how much active maintenance you do, types of materials included, and climate.

If you pile on too much green material, like grass clippings, food scraps, coffee grounds, etc., your pile will start to smell like ammonia. If you start to smell that, then increase your browns (which can consist of pine needles, straw, shredded newspaper, etc.) and turn your pile over to aerate it.

Sometimes the ratio isn’t the problem but how the layers of the browns and greens stack up. If you make a layer of brown or green too thick, then the pile won’t break down properly. If you layer the materials like you would lasagna and spread them out evenly, then the pile will smell as it should. It may take a little trial and error on your part to find the right balance, but by increasing the carbon a bit at a time, then the perfect balance will be found.

Meats, dairy, animal fat, or oils were added

These items should not be in a compost pile used for gardens. Animal-derived products can only be broken down in very large, heated compost piles – which is out of the scope of most backyard composters. “Cold compost” piles, like the ones we’ve described, lack the necessary environment and bacteria to break down these products, so smell is inevitable.

Plus, by limiting yourself to plant-matter only, you won’t have any problems with animals rooting around in your compost!

Missing Microorganisms 

Sometimes, very rarely, the local population of microorganisms will be insufficient to break down newly added materials.

This usually only happens if the compost is isolated from a natural source of microbes (such as dirt). Tumbling composters sometimes suffer this problem because the material is in a plastic tub which is sealed and up off the ground. Or piles of compost could be placed on tarps, and the material isn’t touching the earth. Not only will a pile of compost without microorganisms’ smell, but it also won’t heat up to the proper temperature so that it won’t break down.

Throw away the tarps and tumblers and put your compost on the ground! This will encourage good bugs to migrate into your pile. Alternatively, introduce microorganisms by inoculating your compost with organic soil or fresh compost.

Products To Reduce Compost Odor

Most of the above strategies were for dealing with outdoor compost. What if you’re simply collecting kitchen scraps for pick up? Composting doesn’t happen in buckets, so the smell can definitely proliferate when the bucket is opened.

There are ways to store those scraps without stinking up your kitchen. Below are some items which can help you reduce compost odor:

  • Compost Crock: If you want to store your scraps from the kitchen, but don’t want an unsightly mess or smell, then a compost crock will do it. These are usually made from ceramic or stainless steel and blend in with a counter top or an island. Plus, most of these typically have a charcoal filter, so the contents don’t stink up your kitchen. The cost of a crock usually is between $20 and $60.
  • Compost bucket or pail: The compost pails are an answer for people who have a place in a pantry or cabinet to store kitchen scraps. A pail is a little larger than a crock and comes in steel or plastic. The plastic option cost less than the steel option. The plastic pails come with tight lids to prevent odors from escaping. The steel pails have charcoal filters similar to the ones used in the crocks. The prices for the pails are between $10 and $50 depending on whether you buy plastic or steel.
  • Coffee cans: If there isn’t much waste produced in your kitchen, you can always recycle a steel or plastic coffee can to hold your scraps. By using the lid on top, it makes a convenient sealed scrap holder. You can store a coffee can either in the refrigerator or a cabinet until it’s ready to be emptied. If you place the can in the fridge for storage, it will keep odors under control. Odor control is also possible if you empty and the clean the can out daily.
  • Recycling plastic buckets from paint or detergent: If you purchase your laundry detergent in a five-gallon bucket or if you have one leftover from painting, it will be the perfect solution for kitchen scraps. You need to wash out the container and lid and then begin to start adding scraps. You can even go a couple of days before making a trip to the compost pile because the buckets are so large. However, odors can build up fast in the bucket, but if you add Bokashi mix and you sprinkle some on top every time you add more scraps, it will help to control smells.
  • Recycle plastic bags: Since mostly everyone has plastic bags in their home, they can be used to store scraps. You can place scraps in the plastic bags and then store them in your refrigerator. Then it can be emptied at the end of the day. Or, if you’re planning on starting a compost pile in the spring, you can freeze your kitchen scraps over the winter. Then when you go to work on your compost pile in the spring, you can empty the contents into the pile. Because the scraps are frozen, there aren’t any odors. Kitchen waste, after being frozen, will break down faster in the compost because of the freezing and then thawing process.

Some useful added information

does compost smell

Remember, if you’re adding plants or clippings from your garden, don’t add any which have been treated with pesticides. Plus, if you add ashes to your pile, only add a little at a time because ashes are alkaline. The alkaline will affect the pH in your compost, bacteria for composting works best in neutral to acidic conditions with a 5.5 to 8 pH range. Another great addition to a compost bin is algae and seaweed which need to be washed off first.

You will notice that your finished compost is usually half the volume of what you started working with. This is because although it’s smaller, and it’s much denser. Also, the perfect size for a compost bin is 3′ x3′ x3′. It’s because this is a manageable size for turning and will retain heat while still getting a fresh airflow. Another thing is that compost will decompose the fastest between temperatures of 120-160 degrees Fahrenheit. It will decay at a lower temperature, but it will take longer.

When you add more green materials, the less water you’ll have to add. Also, nitrogen-rich materials such as lawn clippings will collapse during decomposition. If you mix hedge clippings, fibrous material or shredded newspaper, it will improve the air circulation.

Your compost pile should be damp like a wrung-out sponge but not wet. When making your compost pile, make sure that added layer is moist. The surface should stay damp even through the summer months.

If starting a new compost pile, you can help it along by adding aged manure, alfalfa meal, blood meal, compost starter, or cottonseed meal. The microbes responsible for breaking down the organic matter in compost will get a jump start because of the extra nitrogen. Also, if you add corn cobs or woody stems they will decompose slowly. The more material you add to your compost pile at one time, the faster it will heat up. Significant additions of material are better than several smaller additions.

You need to use a hammer or rock to smash them so the microorganisms can break them down easier. Too, if you want to speed the decomposition process when using yard and garden waste, chop them into smaller pieces. When your compost is finished, it should feel and smell like dark, fertile soil. You shouldn’t be able to see any of the items that you placed in your compost pile.

When using worms for composting, remember that worms love coffee grounds. Also, redworms are at their best when the pH is about 7.0, but they can tolerate 4.2 and 8.0 levels. The ideal temperature for a bin of worms is 55-77 degrees. Being that a worm bin is compact, they can be kept in an insulated garage, a basement, or even under the kitchen sink. Plus, worms can be left alone for a few weeks as long as they are fed a little more before you leave. If you’re gone longer than three weeks, you had better have someone come by and check on them.

One of the best worms that can be used in a home vermicomposting system is the Red Wiggler. When in its natural habitat, it will eat large amounts of decaying material, leaves and manure. It will also produce enormous amounts of castings, which will be an excellent addition to any garden. Also, worms can be used to convert pet waste into castings. Because the worms eat odor-producing bacteria, there is not much of a smell. However, you should not use castings from pet waste in vegetable gardens.

Vegetable peels, coffee grounds, fruit rinds, eggshells, tea bags, and most kitchen waste can be fed to worms. But don’t feed them meat and dairy products.

You can soak your compost that is finished in water to make compost tea. This is a nutrient-rich liquid which can be used for watering herbs, vegetables, foliage, flowers, or anything else that grows in your home or garden. You can apply finished compost about 2-4 weeks before planting your garden. This will give the compost some time to stabilize and integrate within the soil. Too, finished compost can be used in the garden any time of the year. It won’t burn the plants or pollute the water, remember, in the garden, there is never enough compost!

To figure out if your compost is ready, grab a handful from the middle of your pile and squeeze. If a few drops of water spill out, your compost is ready to go. Another use for compost is to mulch with it. If you apply a thick layer around plants, then worms will help to mix it with the soil below. Another tip is an excellent potting mix recipe will contain equal amounts of sand or perlite with garden topsoil and compost. Compost by itself is too heavy to be used in containers.

If you want to keep your compost going throughout the winter, keep it in a black plastic bin and direct sunlight. You can also use hay bales for further insulation.

Composting can be fun as well as being green. Cutting down on waste and getting compost for your gardens is an excellent tradeoff for a little time.