When Should You Stop Adding To Compost?

Compost refers to organic material, such as kitchen scrap, leaves, and grass clippings that was composted and turned into soil amendment.

Composting is not only a fantastic way to prevent waste from going into our landfills, but it also minimizes greenhouse gas emissions.

Many gardeners know the value of nutritious, dark, earthy compost and how it creates a healthy and conducive environment for plants to grow.

However, before you have finished compost, there are a couple of things you should know, such as when to stop adding organic material to compost.

Passive composting vs Active composting

There are two methods of composting: cold, or passive composting, and hot, or active composting.

Passive or cold composting is a type of composting where you gradually incorporate organic waste into your pile, but you don’t actively manage it.

This method is also called “set and forget it” because you essentially build your pile and then walk away to let nature take its course.

With this method, your compost should be finished within three to eight months, but sometimes it can take longer. The reason it takes longer is because without managing the compost, the bacteria become less active and the compost temperature drops.

Active or hot composting (also referred to as the batch pile technique), can be made in as little as 6 weeks. Unlike passive composting, it requires continuous maintenance such as turning the pile on a regular basis.

It’s important to point out that unlike passive composting, active composting ensures that the materials are evenly decomposed throughout the pile.

In short, active composting leads to a better finished product.

Image from solanacenter.org

When should you stop adding to compost?

That answer to that question depends on the type of method you choose.

I like to think about hot composting as a single big batch of waste that must decompose evenly over time, and not as something you can keep on adding new material.

In fact, adding new material on top of a batch undergoing decomposition will cool down its temperature and slow down the entire process, defeating the purpose of hot composting, which is to break down waste as quickly as possible.

Some composting professionals argue that you can keep adding materials using the hot composting method, but only when the pile starts to cool down.

Assuming that you have created the pile properly, it reaches peak temperature after approximately one or two days under moderate/warm weather. If you want to use a thermometer (link to Amazon), a temperature between 140 and 160 ºF is hot, so below that point is when you’ll want to add new waste.

In my opinion, to continually add kitchen and yard waste to your compost pile, I believe the best method is passive composting, as you’re free to continue adding new material to the pile as it decomposes.

Furthermore, many individuals are busy and unable to dedicate their time to preparing and maintaining a compost pile, so passive composting is perfect because it doesn’t require that much time or effort.

The issue is that it takes a while for the compost to mature, as it will decay at a relatively slower rate due to the incorporation of fresh waste.

What should you add to your compost?

Kitchen and yard waste is generally what most people add to compost.

If you intend to add new material to an active compost pile, you can do so but you might also slow down decomposition.

To prevent that from happening, a good idea is to add the new material to the central part of the compost as that’s where the bacteria is the most active.

This also makes sure that – regardless of the composting method – you don’t have to turn the pile every so often since it promotes a more even decomposition.

Additional note:

Regardless of the composting method, turning the pile is still a crucial factor in composting because it promotes the circulation of oxygen and allows the ‘working’ microorganisms (bacteria, fungi, etc) to breathe and reproduce.

When is compost finished?

Compost can only reach a finished state when you stop adding to the pile.

Most gardeners point out that even if your compost is no longer active or hot, you should leave it to cure for a while, preferably a few weeks, before you use it in your garden.

To achieve complete decomposition, there are numerous processes that must occur at somewhat cooler temperatures.

For instance, after the death of the so-called heat-loving bacteria, mesophilic bacteria will continue to break down the decaying material at relatively lower temperatures.

Other microorganisms like actinomycetes and fungi are also active at the same temperature to break down things like cellulose and lignin.

Worms also retreat to the pile once the temperatures go down, as they can’t survive the high temperatures required to eliminate disease-carrying pathogens. The same goes for other insects like beetles.

Compost doesn’t go bad or expire, however, if left unattended for an extended period of time, it might lose some of its nutrients.

Therefore, it’s better if you use finished compost as soon as possible.

Signs that compost is ready to use

Don’t spread unfinished compost onto your garden.

Unfinished compost may contain substances that potentially harm your plants, namely pathogens and acids.

Also, unfinished compost is still undergoing decomposition, a process that requires both nitrogen and carbon. Bacteria use these elements to decompose organic matter – which means they’re only available for plants when the process is completed.

For that reason, it’s not recommended that you use unfinished compost because it can pull away nutrients from plant root systems and surrounding soils.

Whether you’ve opted for cold or hot composting, the end product should look more or less the same.

Finished compost is dark, crumbly, and has an earthly smell. The volume of the pile is also reduced to almost half, and the organic materials that were initially added to the compost should no longer be recognizable.

Additional tips:

Some gardeners use 2 or 3 bins to determine the point at which the compost is finally ready to use. The logic is fairly simple – as it involves using one bin to start a new pile while the old one finishes.

Having a single compost bin means you have to wait a couple of months before your compost is done. With two bins, you have continuous, ongoing cycle of compost creation.

If you don’t want to purchase two separate compost bins, a compost tumbler (link to Amazon) can prove handy, as you can find models with multiple compartments. Plus, they’re easy to use.

Compost tumblers are also more efficient, so you can expect to have finished compost in less time than usual.

With that being said, the most important aspect of composting is to guarantee that you have the three core elements at work: a good mix of greens and browns, oxygen, and a tad bit of moisture. All is left is to trust the process.

Final Words

By investing only a small amount of time and effort, you can significantly reduce the amount of waste produced in your household.

Not only that – you can create a product that is extremely useful for gardeners.

Finished compost can improve the soil, helping it retain moisture, while at the same time suppressing plant diseases and pests. It also encourages gardeners to avoid chemical fertilizers that damage the structure of the soil.

In addition, by composting, you’re reducing methane emissions from landfills and lowering your carbon footprint.

Composting is a good way to start contributing to a better environment.