Difference Between Humus and Compost | Top 5 Key Differences

The main difference between compost and humus is that humus is that compost is formed through the aerobic decomposition of organic materials while humus is formed through the fermentation of organic material without oxygen. Humus is the fully broken down, final product of broken down organic materials which can take many years to make.

This article will explore the differences between humus and compost. This includes how they form, how to use them and the break down process.

Differences Between Humus and Compost

Check out my comparison table between humus and compost. The main difference between humus and compost is that humus is fully broken down organic matter while compost is mostly broken down. It will eventually turn into humus over time.

How it formsAnaerobic fermentation (without oxygen)Aerobic decomposition (with oxygen)
What it looks likeDark, crumbly soil, no large piecesSoil like material, still contains some medium sized organic matter pieces
Break down processFully digested organic materialPartly digested organic matter
Continues to break downNoYes
How long it takes to make2-3 years or more6-12 months
Holds water in soil  YesYes
Loosens soil  YesYes
Adds nutrientsYesYes
Feeds worms and soil bacteria  NoYes
Contains nitrogenYes, highYes, small amounts

How humus and compost form – Key Differences

Here are the top differences in the way that humus and compost form.


Humus forms naturally on forest floors where a range of organic materials fall and are broken down. It can be made up of dead leaf matter, animals, insects or fungi. Worms will mix this humus through the soil to improve it over time, provide trees with nitrogen and help to lighten the soil.


Compost will form naturally on forest floors or in your gardens your mulch breaks down on your top soil. This forms when organic material is broken down by soil bacteria and worms with oxygen or aerobically.

A range of materials can be broken down in your home compost or worm bin including food scraps, cardboard, shredded paper and old mulch.

Benefits of humus and compost – Key Differences

Compost is technically partially broken down organic matter so will continue to feed worms and soil bacteria when added to your soil. It will be broken down further into humus slowly over time in the soil as the oxygen runs out.

Humus is high in nitrogen (10:1) and forms naturally in environments where organic matter is broken down without oxygen by soil bacteria. Compost is lower in nitrogen but this nitrogen will slowly be release to your soil as bacteria continue to break down the elements of the compost.

Compost is ready the organic matter is broken down so you can no longer tell which ingredient is rich. Humus is a rich, dark material that looks like light, crumbly soil.

What is compost?

Check out the main things to know about compost so you can see the difference between compost and humus.

Compost can be made out of a range of materials including fall leaves.

What compost is made of

Compost is made up of decomposed organic matter, can make it at home from food scraps, coffee grounds and fall leaves or it will naturally form on the forest floor or on the top of our garden beds.

Compost contains a small amount of humus that will continue to form over years.

When compost is done

Compost is considered done or finished when it resembles light crumbly soil. Most of the pieces will have been mixed through and are broken down you won’t be able to see the separate materials. Food scraps and straw will be broken down but there may be a few larger pieces left.

Compost will continue to break down even further when you leave it for longer or dig it through your garden soil.

Finished compots is dark, brown and great for your soil.

Benefits of compost

Compost is used to improve and lighten clay or sandy soil, it can add nutrients and organic matter to your vegetable garden or be dug through the soil before planting new trees. You can mix compost through potting soil to add extra nutrients or use it as a top dressing for trees in spring.

Compost will lighten the soil, add a small amount of nutrients, help the soil to hold water for longer and help plant roots to spread far and stabilize the plant. It will also feed worms and soil bacteria which will continue to break down the compost in the soil over time.

Compost can also be used as a mulch or top dressing for established plants and will help to stop weeds from growing, keep water in the soil and will gently feed the plant over time.

Compost can be made at home faster than humus which can take years to form. A good hot composting pile can create compost within 4-6 weeks or a cold compost will take anywhere from 6-12 months to be ready to use in your soil.

What is humus?

Check out the main facts about humus and how it compares to compost.

What humus is made of

Humus is made of fully decomposed organic matter. It will look dark and similar to light crumbly soil with no visible pieces of any particular material. There will be no remnants of straw, hay, leaves or food scraps. It will look dark, almost like coffee grounds. not be broken down any further. It is high in carbon and will contain the digested nutrients from the compost material.

When humus is done

Humus is done when it looks dark, crumbly and light in texture when it is done. Small amounts can be found on the forest floor where old trees have fallen and are beginning to break down anaerobically at the base. It can look dark and sludgy if there is water around.

Benefits of humus

Humus is a fantastic ingredient to improve soil structure, help to loosen clay and hold sandy soils together, to add nitrogen to the soil and generally improve plant growth.

Humus can hold up to 90% of its weight in water so is a great addition for drought stricken areas.

Difference Between Humus and Compost | Summary

Compost is made from broken down organic matter, is great for improving soil and can be easily made at home. Humus is formed through the natural anaerobic fermentation of organic matter and happens on both forest floors and naturally in your compost over time. It is best to aim to make compost and humus will naturally form in your soil as the compost continues to break down.

Happy growing.


BDPedia, About: Humus, https://dbpedia.org/page/Humus, accessed 9/3/22.