The Perfect Compost Ratio: Greens to Brown Balance

Belen Molina 2021-06-15 8 min

Have you already tried making compost at home and failed? Well, let me tell you that as happens in the kitchen there are certain rules to follow so that you can achieve the perfect compost. But which are these rules? Let me introduce to you the concept of the compost ratio of green to brown. A balance between greens and browns that will save your life (or your sustainable soul at least). Continue reading the article to discover the secrets.

What is the C:N Compost Ratio?

The compost ratio is the desired balance between carbon-rich ingredients and nitrogen-rich ingredients. I know that at this moment you may be thinking: but what does science have to do with compost? Everything. Compost piles require four elements to fully work: carbon, nitrogen, oxygen and water. Let´s first explain some terms.

Carbon-rich ingredients represent the browns in a compost pile, whereas the nitrogen-rich ingredients represent the greens. As a reminder, typical browns are dried leaves, cardboard and paper, straw and some more. While typical greens include fresh leaves, vegetable and fruit scraps, flowers, eggshells, etc. Each of those ingredients has a specific amount of carbon and nitrogen. For example, coffee grounds are 20:1.

If you want more information about this, check the following article: How to make a Compost Pile? All you need to know about it

Sweet-smelling compost

Scientists asserted that the key to achieve a sweet-smelling compost is to keep a carbon to nitrogen ratio of about 25/30 parts of carbon to 1 part of nitrogen (25/30:1). The reason for this is that the microbes involved in the composting process decompose the organic matter of the compost pile. To do such a process, they nurture themselves from carbon and use nitrogen to build their cell structure.

The above mentioned “growth” of microbes results in a fast and successful composting process and also the compost pile arrives to suitable temperatures. When this compost ratio is lower than the standard, you may experience issues with your compost, such as ammonia odor due to an excessive amount of nitrogen or greens.

When it is higher than the standard, the compost will seem dry due to an excess of carbon or browns. Arriving at the ideal ratio will accelerate the decomposition process enormously.

However, we know that the majority of people don't have the time to stop before composting to analyze which organic material represents carbon or nitrogen. That is why we will try to simplify your life.

pexels-photo-8219462
Maria Naichenko, from Pexels

Difference Between Ratios

It is important to mention that the carbon: nitrogen ratio and the compost ratio of green to brown are not the same. As we mentioned before, at your home you will be able to count buckets of browns and greens instead of atoms and molecules. Greens will help you enlarge nitrogen concentration and browns will help you reduce that concentration.

After all this knowledge you may wonder, but how can I know the C:N ratio of the materials? Luckily, each material has its corresponding C:N ratio. Read the list of greens and browns appearing below to excel at your compost ratio of green to brown.

Approximated Carbon:Nitrogen Ratios

GREEN (NITROGEN)

Food scraps

17:1

Vegetable scraps

25:1

Aged chicken manure

7:1

Coffee grounds

25:1

Grass clippings- Fresh

17:1

Fruit wastes

25-40:1

Weed

30:1

Garden waste

30:1

Seaweed

19:1

Fresh weeds

20:1

Farm manure

90:1

BROWN (CARBON)

Straw, Hay

90:1

Leaves

60:1

Sawdust

500:1

Wood chips

400:1

Nut shells

35:1

Shredded newspaper

175:1

Pine needles

80:1

Corn stalks

60:1

Grain hulls

80:1

Shredded cardboard

350:1

How can you calculate the perfect compost ratio of C:N?

When you add two parts of a green material to one part of a brown material to your pile you will achieve the C: N compost ratio. But how can you calculate it? A part of a material is simply a certain quantity of it. The calculation you can do is summing up the carbon side ratio of the materials you have, then divide that result by the number of materials.

The resulting number will reveal the truth. Based on that number, you will decide whether to add more greens/nitrogen or add more browns/carbon.

Let's imagine that I have vegetable scraps, aged chicken manure and leaves as materials for my compost. The sum will be 25,7,60 and divide by the material´s quantity, i.e.: 92/3 equals 30:1.

Benefits of achieving the perfect compost ratio of green to brown

As the ecologist lover that you are, I am sure you know some of the benefits of compost. The organic matter decomposed through that process can be used as a fertilizer and soil amendment. You can put that natural fertilizer on your garden and your plants will grow faster and stronger. It is better than using chemical fertilizers and it is also cheaper. Apart from that, you can reduce the garbage at your house at huuuge levels. Statistics show that food scraps and yard waste equal more than 30% of the garbage that we keep at home! Composting boosts the creation of humus, which results from the decomposed organic matter. Also, your waste remains in your garden in a different form instead of going to the landfills. There, garbage releases methane that affects the ozone layer.

By composting you can get the best of both worlds: help the environment and improve the quality of your soil and plants.

pexels-photo-6510855
Tima Miroshnichenko, from Pexels

Follow these steps for good results!

When you get to achieve the compost ratio of green to brown in your compost pile, the results will be seen immediately.

  1. Take your time to divide the materials that you count with at your home.
  2. Try to use the table that appears at the beginning of the article to identify your greens and browns. Remember to take into account the compost ratio to have a balance of browns to greens. A good advice is to alternate layers of different sized materials so that everything can be perfectly integrated.
  3. Pay attention to the water amount that you put on the compost pile. It is essential to add water since it moisturizes the pile and helps to disintegrate the organic matter.

Tips to Excel at Your Compost Ratio of Green to Brown

  • Be Careful with the Compost Temperature,

In hot composting the C:N ratio is super important. High C:N ratios will result in a stinky and ammonia odor compost. That doesn´t occur in cold piles since the off gassing of nitro only takes place under thermophilic conditions. Not only will the compost ratio of green to brown accelerate the composting but it will also help the pile to reach a hot temperature.

  • Select Materials of Different Sizes,

Since they allow the entrance of oxygen into your compost pile. The oxygen will help the microorganism’s growth and the results will be seen in a short time.

  • Think in dry and wet materials,

Materials as browns (carbon) and in wet materials as greens (nitrogen). Green material is usually found in your garden or at your household, while browns are more difficult to obtain. Picturing those concepts in your head will make everything easier.

  • Remember...

Woody materials and chips are hard materials to break easily, they spend more time decomposing. That is why it is better to replace them with fallen leaves for example and leave those materials for another activity.

woody materials and chips
Jorge Urosa, from pexels
  • Avoid Composting Diseased foliage

You better burn them.

  • Become an Odor Expert with your compost pile

One excellent advice is to train your smell to have a perfect compost balance. Whenever you smell something similar to rotten eggs means that you need to make a change. Add more greens and you will witness the miracle in a few days.

  • Do not Compost dairy products

Such as sour cream and eggs. They cause disgusting odor and bring rats to your compost.

Consequences of Having a Wrong Compost Ratio of Green to Brown

If you think that something is wrong with your compost pile, check these hints:

  • Odor:

If your compost smells like putrid food then you need to revise the nitrogen materials added to your pile. Probably there is an excess of them so you will need to counteract the effect by adding carbon materials (browns).

Compost bin, full of ingredients
Gareth Willey, from pexels
  • Too Much Water:

The microorganisms of your compost pile need the right amount of water and air to grow. If the pile is soggy it won't be able to provide the organisms a good living space. Instead, anaerobic bacteria will take their place. What are anaerobic bacteria? They do not need oxygen to survive since they don´t live or grow when there is oxygen present. They end up slowing the process of composting and produce a smell in your compost.

  • Too Little Water:

Despite excess water isn't good for your compost ratio of green to brown, neither is a little amount of water. The right amount of water will result in a faster decomposition of organic materials; hence you will obtain results more quickly. You can notice the lack of water by revising the compost pile.


Although it may seem difficult to have a great compost ratio, it is easier than you think. I encourage you to take into account all the advice given in the article and process the information calmly. Trust your gut on the process!

Belen Molina

I am a passionate person about healthy food and the environment. Translator/copywriter.

Read other articles from this writer
+TOP
Related articles