What Is Compost And What Does It Do?

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You can’t look into gardening without coming across the term ‘compost.’ Whether it’s store brought or homemade, compost is intrinsically linked to backyard gardening.

Gardeners will always tell you their secret to good compost, and it will inevitably be different depending on whom you’re talking to.

What is composting? Composting is a natural process that can be sped up to meet your needs, producing a nutrient rich additive that will enhance your topsoil and make it more fertile.

In this article I’m going to cover what is compost, how you can make it at home, and understand the benefits of compost to your garden.

What is Compost?

Compost is organic matter that has broken down into a nutrient-rich soil amendment for plants to thrive in. It’s a magical process that turns kitchen scraps, yard waste, and other organic materials into what gardeners call “black gold,” or usable compost.

This organic material absorbs nutrients during its lifespan, and it’s these same nutrients that we want to add back into our soil.

By composting, we are collecting nutrients and redistributing them back into the soil to feed our plants and help them grow. Compost reduces the need to add chemical fertilizers into the soil.

Composting is simply creating a space where organic matter can fully decompose, then taking that decomposed matter and using it to feed your plants.

This composting process can take anywhere from a couple of weeks to six months. Different materials decay at different rates, so by mixing up the materials you can speed up the overall decomposition of the matter on your pile.

There are many different ways to compost, from using a compost tumbler or compost bin, to enclosed worm factories and open compost heaps. Whichever way you try, the end result will be a wonderful additive for your garden or your potted plants.

Compost will add back any nutrients that have been used by your plants, so it is especially good to use if you are growing vegetables. Adding in compost regularly is the best way to keep your soil healthy and fertile.

What are the Benefits of Composting?

What does compost do, what is compost for, and why do you want to start composting? It’s a common question for people wondering if it’s worth the effort – which it is!

Composting is a process that transforms organic materials into a nutrient-rich fertilizer for plants. By diverting waste from landfills, composting reduces the cost of waste management and helps to protect the environment.

Composting also improves the soil quality, leading to healthier and more productive plants. Here are the key benefits of composting:

1. Adds Nutrients and Organic Matter to the Soil

Compost is rich in nutrients that plants need to grow, such as nitrogen, phosphorus, and potassium. When compost is added to the soil, it provides a slow-release source of nutrients that plants can absorb over time.

Compost also improves the soil structure by adding organic matter, which helps to aerate the soil and increase its water-holding capacity.

2. Increases the Moisture Holding Capacity of Soil

Compost can hold several times its weight in water, which means it can help to reduce the need for irrigation. By adding compost to the soil, you can increase its ability to retain moisture, which is especially useful in areas with low rainfall or during droughts.

Compost also helps to prevent soil erosion by stabilizing the soil and reducing runoff.

3. Reduces the Need for Fertilizers and Pesticides

When you add compost to the soil, you are providing a natural source of nutrients that can replace synthetic fertilizers. Because compost releases nutrients slowly over time, it can reduce the risk of over-fertilizing or burning plants.

Compost also contains microorganisms that can help to suppress plant diseases and pests, reducing the need for pesticides.

4. Immobilizes Pollutants

Compost can help to immobilize and degrade pollutants in the soil, such as heavy metals and petroleum products.

The microorganisms in compost break down these pollutants into harmless compounds, which can reduce the risk of contamination of groundwater or surface water.

Compost can also help to improve the health of habitats by restoring degraded soils.

5. Reduces Waste in Landfills

Composting helps to divert organic waste from landfills, which can reduce the amount of methane gas produced by decomposing waste. Methane is a potent greenhouse gas that contributes to climate change, so reducing its emission can have a significant environmental impact.

Composting also reduces the need for landfill space, which can save money and reduce the environmental impact of waste management.

Read more about Composting Pros and Cons

What is in Compost?

Compost is made up of organic matter. Gardeners use many different types of organic materials in their compost for their organic gardens. Basically, anything that was once alive in the environment can be added to your compost.

Of course, there are practical limitations to this, and you will have to get a good mix of different kinds of matter to get good compost. A compost heap, or composter, should contain different decaying organic materials.

Gardeners categorize organic matter into two groups: Greens and Browns.

  • Greens are materials that are high in nitrogen, they break down quickly and usually contain a lot of moisture. Greens are things like plant material (grass clippings, weeds) and food waste from fruits and vegetables.
  • Browns are high in carbon, they are slow to break down and are usually dry. Browns are things like wood products, mulch, straw, leaves, newspaper, and shredded paper.

Green materials help to break down browns. Browns keep the compost aerated and stop it from becoming too sludgy and smelly. Good compost is usually a 50/50 mix of greens and browns.

Green and brown materials must be mixed together to create a decent compost collection. Many people are under the misconception that compost is smelly, but a smelly compost heap usually indicates an imbalance in nitrogen and carbon.

Foul odors coming from a compost heap usually mean that there is too much nitrogen. You should add more brown matter to balance it out and neutralize the bad odor.

The resulting  compost in the ideal environment has a lovely earthy aroma, and looks like rich earth to grow healthy plants. 

How Does Composting Work?

The aim of composting is to create conditions that are ideal for the natural decomposition process to take place. The ingredients for composting are: organic materials, microorganisms from the soil, water, air, and heat.

Microorganisms eat and excrete the organic matter, and break it down using aerobic decomposition. These microorganisms require both air and water to survive and multiply.

An actively managed pile can produce compost in about a month, otherwise it can take up to six months or more for the compost to form enough to become useful fertilizer. 

Through this process, the microorganisms radiate heat and give off carbon dioxide. A healthy compost pile can reach temperatures in excess of 150 degrees Fahrenheit.

As well as generating heat, compost heaps need heat to aid the breakdown of materials. The ideal temperature range for a compost heap is 135° to 160°F.

Any warmer and the thermophilic organisms won’t be able to continue to decompose the materials. Also, if the temperature gets too high, the beneficial bugs and worms will not be able to survive.

Compost microorganisms work best in conditions that are neutral to acidic, with a pH balance of 5.5-8. Acidic conditions will promote the growth of fungi and the breakdown of cellulose and lignin.

A compost pile is actually a complex ecosystem of its own, housing numerous beneficial composting organisms. Bacteria and fungi are the first to start breaking down organic materials.

The bacteria and fungi then feed mites, single felled organisms called Protozoa, and tiny worms called nematodes. These are then eaten by predatory nematodes and mites, as well as other bugs like millipedes and beetles.

All of these organisms, along with worms, ants and wood-lice, aid the breakdown of organic materials and help to form the nutrient rich fertilizer.

Compost can be dug into the soil, or laid on top for the nutrients to be watered in. You can even make compost tea that you can use to water your plants and give them a boost of nutrients.

Types of Composting

How do you compost? When it comes to backyard composting, there are two main composting types: cold and hot composting.

1. Hot Composting

Hot composting is an excellent method for breaking down organic materials quickly and efficiently. This method relies on the perfect balance of high temperatures, oxygen, water, and organic materials. With the right mix, hot composting can produce black gold.

This type of composting process involves the use of high temperatures, which speeds up the breakdown of materials and results in the production of usable compost within just a few months.

The higher temperature not only accelerates the speed of decomposition, but also destroys any harmful pathogens, bacteria, fungi, protozoa, worms, or parasites that may be present in the organic waste.

Hot composting requires more management, as the pile needs to be turned and maintained to ensure that it reaches and maintains a high temperature.

Cold Composting

Cold composting is the more passive method of the two, requiring little management beyond adding organic waste to the pile. This method relies on the slow decomposition of materials that occurs naturally over time.

While this method does produce usable compost, it may take up to a year or longer to fully break down, depending on the ratio of compost ingredients used.

Unlike hot composting, cold composting does not require any artificial heat or forced decomposition. Instead, it relies on nature to do its work over time.

To start cold composting, simply layer your brown and green materials in a pile, making sure to give them enough airflow and moisture to break down naturally.

The great thing about cold composting is that it doesn’t require constant maintenance. You can let the pile sit for up to a year or more, allowing nature to do its slow and steady work. The end result is a usable compost that’s just as nutrient-rich as the hot composting method.

Which Type of Composting is Best?

Both cold and hot composting can be effective methods for turning organic waste into usable compost, but the choice between the two depends largely on the amount of organic waste to compost and the time and effort you are willing to put into the maintenance of the pile.

If you have a larger amount of organic waste to compost and are willing to put in the extra maintenance, hot composting may be the way to go. However, if you have less organic waste and want a more hands-off approach, cold composting may be a better choice.

Additionally, those concerned about weed seeds or pathogens may opt for hot composting, as the high temperatures will help prevent them from spreading.

Regardless of which method you choose, it is important to maintain a proper ratio of compost ingredients and to regularly turn and aerate the pile to ensure that oxygen is present and that it does not become anaerobic.

An oxygen-rich environment will allow beneficial bacteria and other organisms to thrive, breaking down materials more quickly and producing a higher quality compost.

Regardless of which method you choose, proper management and maintenance are key to producing high-quality compost. You want compost that is free of harmful pathogens, weed seeds, and other contaminants, and can help improve plant growth, all the while reducing the need for pesticides and herbicides.

What Can Be Composted?

Pretty much any organic materials can be composted, although there are a few things that you’ll want to avoid. Let’s take a look around your home and life to see what things you can compost:

Things to Compost From the Garden and Lawn

From your lawn and garden, you can compost:

  • Plant trimmings and cuttings
  • Dead plants
  • Grass clippings
  • Dead leaves
  • Twigs
  • Branches
  • Wood chips

Things you’ll want to avoid are any plants that are showing signs of disease. They should not be added to your compost as you run the risk of spreading plant diseases.

Things to Compost From the Kitchen

Many things from the kitchen are perfect additions to your compost: 

  • Food scraps like fruit and vegetable scraps, like peelings
  • Old fruit or vegetable waste that is no longer edible
  • Egg shells
  • Stale bread, cereal, pasta
  • Used teabags and tea leaves
  • Used coffee grounds/grinds
  • Paper towels and egg cartons

Some people compost cooked food, but I advise against it because they might attract unwanted pests. Raw meat should also be avoided for the same reason.

Raw and cooked meat can also harbor harmful bacteria and pathogens, so it’s best avoided altogether.

There are some composters on the market that are designed to compost cooked food, but if you have an open pile, then it’s best to avoid foods that will attract scavengers.

Kitchen composting is one of the best and main sources of compost ingredients. 

Things to Compost From Home

Items you can compost in your home include:

  • Newspapers
  • The cardboard inner tube of toilet rolls
  • Hair
  • Nail clippings
  • Scrap paper
  • Cardboard (Learn more about cardboard composting)
  • String
  • Items made from natural materials like silk, cotton or wool.

Things to Compost From Pets and Animals

Animal products are a popular, natural organic waste to add to the pile. If you have pets, they can provide compost material:

  • Pet hair and feathers
  • Pet waste and droppings, preferably if your pet is an herbivore and fed fresh fruits and vegetables

Farm animals and other larger animals like horses, cows, and chickens can provide manure, but only if from herbivores (vegetable and plant eaters, non-meat). 

Fresh manure is too strong to use directly in your garden though. It must be left to decompose for at least a month before being used. Adding it to your compost is the ideal solution.

If you have cats, learn more about composting cat poop and cat litter here.

If you have dogs, learn more about composting dog poop here.

Compost Recycling and Uses

Composting is the ultimate form of recycling, plus it is free and easy to do. If you are a gardener, then there’s no reason for you not to compost. Compost can be useful in many ways and will definitely benefit your garden and the environment. 

Even if you aren’t a gardener, you can still have a go at composting! Composting reduces landfill waste as well as harmful greenhouse gas emissions.

Nearly 25% of waste in the United States is actually compostable materials. That’s a staggering 65 million tons of waste that could have been used as compost.

If you like the idea of composting but don’t think you’d use the end result, there are still things you can do with the compost. You could:

  • Give it away to any gardeners you may know
  • Advertise free compost to collectors on Craigslist
  • Donate it to a school or community garden
  • Give it away to a local farm or landscaper.

If you’re feeling particularly rebellious, then why not have a go at some guerrilla gardening!

You could add a bit of compost to the topsoil of local trees, or brighten up your neighborhood by sprinkling some wildflower seeds into it and depositing it in suitable spots.  

Final Thoughts on Composting

The compost process can be quite a magical experience, watching your waste turn into nutritious fertilizer that will feed your vegetables, which in turn will feed you.

There is something very rewarding about digging out compost that once was trash. Composting is very beneficial to our environment. We need to start thinking about how we recycle more often. The benefits of using compost outweigh its drawbacks.

If you don’t have the space for a large composter, check out worm farms. These can be used indoors and will turn your kitchen waste into compost with the aid of some friendly worms!

What is Compost FAQs

What is compost made of?

Compost is made of all sorts of different ingredients including food scraps, grass clippings, leaves, wood chips, straw, sawdust, coffee grounds, eggshells, tea bags, etc. 

How do you make compost?

You can make compost yourself by adding these items to an outdoor bin and leaving them alone until they break down over time. This takes anywhere between a few weeks to six months, and even longer depending on the materials. 

Can you buy compost online?

Yes, you can purchase bags of compost online through websites such as Amazon.com

What should not go in compost?

Materials that should not go into compost include: cooked food, meat, dairy products, fish, eggs, oil-based foods, plastics, batteries, paints, cleaning supplies, chemical pesticides, chemical fertilizers, animal bedding, diapers, sanitary napkins, cotton balls, tissues, styrofoam, balloons, condoms, tampons, toothpaste tubes, toilet tissue rolls, plastic wrap, aluminum foil, tin cans, glass bottles, metal utensils, and styrofoam. 

Does compost turn into soil?

No, compost does not turn into soil. Compost is a soil amendment that’s mixed with topsoil for use in gardens. 

What is compost used for?

Compost is commonly used in home gardens and landscapes because it adds nutrients back into the soil. In addition, it helps prevent weeds from growing. 

When is compost finished?

Compost is finished and ready to be used once it has broken down enough so that it no longer smells bad and doesn’t attract pests. It will look and smell like rich, fertile soil when done. 


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Written by:

Denise Davis
I am an avid gardener who has spent most of her life in the garden, growing and cultivating organic veggies for friends and family. I love the earthy smell of composting and making homemade fertilizers from natural ingredients like old coffee grounds or eggshells. Gardening is a great way to get outside, learn new things about nature, exercise your body (and brain!) and eat healthy food you have grown yourself!