What is Composting and How Does It Work?

Last Updated on March 15, 2022 by Admin

You’ve heard about it. But, aren’t sure why people bother do to it.

Well, if you’ve been wondering about what composting is, how to do it and where you can use it, this guide’s for you.

Contrary to what many people believe, composting is not complicated. Once you understand what’s happening and what you need to do to make those things happen, it’s pretty straightforward.

So, follow along. By the end, you’ll be able to start composting in your backyard.


What Is Composting?

Composting is a method of waste disposal where items such as leftover food and grass clippings are allowed to decompose naturally. During this process the organic materials are broken down by microorganisms like worms and bacteria with a little help from oxygen-rich air and water. The latter two components speed up the decaying process.

What you end up with is a crumbly, dark brown product that looks like chocolate cake. And, contrary to what you might think, it doesn’t smell bad.

This final result of composting is called humus, which is the organic material that occurs in soil when plants and animals decay. And, it is what all the months of composting were for.

In short, well-aged compost (when done correctly) leads to humus.


Why is Humus Important to Soil?

Humus gives soil its crumbly structure. Its looseness allows for more air to circulate and water to flow through your container or garden soil.

Additionally, humus contains many nutrients that are beneficial to your plants, including nitrogen which promotes healthy foliage development and overall plant growth.

One of the most important properties of humus is its ability to hold water. In fact, it holds 90% of its weight in water.

This allows the soil surrounding your plant to stay moist for longer periods so that the roots can absorb the moisture. As such, it reduces the frequency with which you have to water your plants or crops. And, it keeps them from drying out.

So, besides being an environmentally-friendly way to get rid of waste products, composting also helps improve the quality of your soil via its byproduct, humus.

That said, it’s important to note that just because you started with a large pile of compost, it doesn’t mean you’ll end up with a similarly sized pile of humus.

That’s something I learned (among other things), the first time I tried it.


Only a portion, well, small portion to be exact, of your original compost pile turns into humus. The rest just disappears into carbon dioxide, water and a few other minerals.


Is Compost a Fertilizer?

This is one of the most common questions I get, probably because you may have heard some people say that “compost is a fertilizer”.

So, the answer to the question is both yes and no.

Here’s why.

  • Yes. Compost can be considered a type of fertilizer because it improves the quality of your soil. It contains 6% nitrogen and some smaller percentages of phosphorus, sulfur, calcium and magnesium among other things. These are all nutrients your plants need to grow and maintain good health.
  • No. However, compost does not contain all the nutrients that fertilizers do. And, depending on what you want to get out of your plants, be it foliage growth, blooms, etc., you may want to increase certain nutrients. Those are things you can’t fully or accurately control with humus.

As such, humus is not equal to fertilizer.

Instead, a better way of putting it is that humus complements fertilizer. Why?

That’s because fertilizer contains all the important nutrients needed by soil. These include the big 3 which are nitrogen, phosphorus and potassium.

However, your plants also need water and air, among other things.

That’s where humus comes in. Humus not only boosts the organic matter in soil, it also improves its structure by loosening it and allowing it to retain more moisture.

Thus, adding humus improves the soil you inherited with your garden. In most cases, that includes poor quality soils like clay, sand and other heavier kinds, all of which come with these unpleasant qualities.

  • They’re compacted or can easily become compacted. When this happens, air or water won’t easily flow through. It also prevents your plants’ roots from burrowing themselves deep into it.
  • Don’t drain well. Thus, retaining too much moisture
  • Low in microorganisms like beneficial bacteria and fungi
  • Don’t retain the nutrients from your fertilizer well

Humus helps fix all of that.




How Does Composting Work?

Now, it’s time to get your hands dirty. But, before getting to the actual process, one of the most important things to know is what you can and can’t put into your pile.

Unlike a trash bin, you can’t just put everything into your compost heap. Otherwise, it will smell, look and feel like garbage.

Instead, you’ll need to meticulously choose what you’ll include and exclude.


What Can You Compost?

When it comes to the ingredients of your compost pile, it all comes down to one thing: organic matter. And, withing that, you specifically want:

  • Items that are rich in carbon
  • Items that are rich in nitrogen

When mixed together with some water, these two types of material will turn into “black gold”.

What can you include in compost pile
What can you include in compost pile

Here’s a chart that shows the C:N ratio of different compost components. On the left you have carbon-rich materials or browns. On the right, you have nitrogen rich materials (greens).

Carbon to Nitrogen Ratio. C:N Ratio of carbon rich materials and nitrogen rich materials for composting
Carbon to Nitrogen Ratio. C:N Ratio of carbon rich materials and nitrogen rich materials for composting


Carbon-Rich Materials for Your Compost Pile

These are the browns. Once you see the list below, you’ll know why.

It’s because most of them are brown or some shade of the color.

As you’ve learned above, the creatures inhabiting your compost pile need food, which they convert into energy.

That’s why high carbon materials are an essential element of your compost pile. These include:

  • Dry leaves
  • Hay
  • Sawdust
  • Wood trimmings from your garden like twigs and stems
  • Paper products including cardboard, paper towels, shredded paper and newspapers
  • Pine needles
  • Straw
  • Cotton fabrics (make sure they’re 100% cotton)
  • Stalks from vegetables
  • Peat moss

Here’s the chart from above again. But this chart only shows the carbon-rich materials and each of their C:N ratios.

carbon to nitrogen ratio browns
carbon to nitrogen ratio of carbon rich materials (browns)


Nitrogen-Rich Materials for Your Compost Pile

In contrast, these are the greens. Again, it’s because many of them are green or greenish in color. Although, there are a few exceptions.

While the high carbon ingredients provide microorganisms with energy, the nitrogen-rich components are responsible for building their cells. That’s because they provide proteins which are the building blocks of cells.

Here are some the most common nitrogen-rich materials used for composting.

  • Grass clippings
  • Leaves
  • Coffee grounds
  • Manure
  • Kitchen waste
  • Teabags (including the bag)
  • Feathers
  • Fur
  • Hair
  • Old houseplants
  • Eggshells
  • Aquarium water
  • Kelp
  • Seaweed
  • Algae

Here’s the chart similar from above. However, this only shows the chart of nitrogen-rich materials and their respective C:N ratios.

carbon to nitrogen ratio of nitrogen-rich materials (greens)
carbon to nitrogen ratio of nitrogen-rich materials (greens)


What Shouldn’t You Compost?

Similarly, there are some items you should never add to your compost. That’s because they can cause it to go rancid, attract animals, introduce diseases, chemicals and other harmful things.

Since you’ll be applying the end product of the composting to your soil, you don’t want any trace of these materials in the humus.

As such, it’s a good idea NOT to put any of these items in your compost heap.

  • Waste from pets including dogs, cats, and birds
  • Grease, different kinds of fats, and oil
  • Anything with dairy
  • Meat and their bones
  • Ashes from wood or charcoal
  • Wood that’s been treated with chemicals
  • Anything synthetic
What you should not include in compost pile
What you should not include in compost pile


How Do You Speed Up the Compost Process?

If you’ve looked around stores both on- and offline, you’ve probably seen some products meant to speed up your compost.

In all likelihood, you don’t really need any of them. As long as you get all the right ingredients into your pile or bin, you’ll be fine.

That said, if you’re in a hurry and want to speed up the entire process as much as you possibly can, it’s good to know what’s out there. And, what each of the products can do.



These are loaded with nitrogen. As such, they’re designed to speed up the decomposition process. They’re an alternative to adding more greens to your pile, which achieves a similar result.

Here, you’ll find different options including artificial and organic options.

Chemical options include all sorts of compounds that have some kind of nitrogen in them. Among these is ammonium nitrate fertilizer.

But, do be careful with this because using it incorrectly can make your pile smell like ammonia. I don’t think I need to tell you how bad the odor is.

If you do decide to add an activator, do go with the organic one. These make use of natural sources including blood meal, seaweed and poultry waste.

You can get them in both box and bag forms. And, they’ll include other nutrients as well.



If you don’t want to wait for the microorganisms to arrive at your compost heap, you can add them yourself to jumpstart the entire process.

Inoculators are products that contain these microorganisms. As such, introducing them to your pile increases the number of decomposers in it.

Like the activators, there are a few variations of inoculators as well.

Some come in tablets that dissolve. When they do, they release bacteria and fungi that get to work. Additionally, there are also those that are made from different plants including nettle, dandelion and chamomile.